2023 Vol. 40, No. 1

Research status and development trend of electromagnetic absorbing materials
WANG Yifan, ZHU Lin, HAN Lu, ZHOU Xinghai, GAO Yuan, LYU Lihua
2023, 40(1): 1-12. doi: 10.13801/j.cnki.fhclxb.20220512.005
With the wide application of electronic equipment in military, communication, medical, transportation and other fields, the problems of electromagnetic interference and electromagnetic radiation are increasing. Wave absorbing materials can convert the electromagnetic wave energy into heat or other forms energy, which is a direct and effective means of electromagnetic pollution prevention and control. Therefore, researchers at home and abroad have invested a lot of research on the development and application of high-performance wave absorbing materials. Based on the current research status at home and abroad, the paper briefly summarizes the absorption theory and the classification of wave absorbing material. In addition, the paper focusses on the enhancement of electromagnetic adsorption performance from the structural design of materials. Finally, this paper prospects the development trend of wave absorption materials from the direction of compatibility, composite, intelligence and eco-friendly. The paper aims to provide research ideas and theoretical basis for the development of new and high-performance wave absorbing materials.
Research progress of fiber reinforced composites by grinding technology for hole making
CHEN Bing, XU Hu, WANG Jian, SU Fei
2023, 40(1): 13-37. doi: 10.13801/j.cnki.fhclxb.20220419.008
For the excellent physical, chemical and mechanical properties of fiber reinforced composites, they are widely used in high-tech fields such as aerospace, automobiles, and new energy. Compared with traditional drilling and milling tools, less defects are generated when machining holes of fiber reinforced composites by abrasive tools, such as delamination, burrs, tearing and thermal damage after processing, especially, fiber reinforced ceramic matrix composites with higher hardness could be stably processed when using abrasive tools. In this paper, hole making mechanism of grinding fiber reinforced composites is reviewed, including chip formation, grinding axial force, grinding temperature, and so on. And then, the research status of hole making defects and their evaluation methods are discussed. Subsequently, hole-making quality and its influencing factors are analyzed. Besides, the abrasive tools for grinding fiber reinforced composite holes and their wear mechanisms are summarized. Finally, the development trends of grinding holes for fiber reinforced composites are concluded and forecasted.
Research progress on the hierarchical structure and mechanical behaviors of phloem fibers
CHEN Bingwei, KAN Yu’na, ZHAI Shengcheng, PAN Mingzhu, WANG Xinzhou, MEI Changtong
2023, 40(1): 38-50. doi: 10.13801/j.cnki.fhclxb.20220512.004
Phloem fiber (or Bast fiber), a kind of non-woody plant fiber, is widely used to reinforce composites due to its good mechanical properties and eco-friendliness. In the cell wall of phloem fiber, abundant cellulose microfibrils with the helical structure are embedded in an amorphous matrix composed of hemicellulose, pectin, and lignin. The variation of the cellulose microfibril angle forms a highly ordered hierarchical structure of the cell wall. The assembly structure and compositions at different scales are of great significance for mechanisms and principles of the excellent mechanical performance of phloem fiber. This work summarized the structural characteristics of phloem fibers represented by hemp and flax at the tissue level, cell wall level, ultrastructural level, and molecular level. The emphasis was focused on the underlying interactions at different levels which generated the special mechanical behavior of the phloem fibers during the axial stretching process. Finally, the existing problems were pointed out, and the development trends of future research were prospected. The extracted concepts may provide new ideas for improving the utilization of phloem fiber and serve as inspiration for biomimetic applications.
Application progress of nano-materials in detection of antibiotics by electrochemical sensors
YAO Congcong, WEI Jianqiang, LIN Jinyu, LU Qiuyue, QIAN Junchao, CHEN Feng
2023, 40(1): 51-61. doi: 10.13801/j.cnki.fhclxb.20220412.001
Since the discovery of antibiotics, they have been widely used in the prevention and treatment of bacterial infections because they can hinder the growth of bacteria. However, the abuse of antibiotics in animal husbandry and agriculture leads to antibiotic pollution, which greatly threatens the safety of water sources, increases bacterial drug resistance, and brings great harm to the environment and human health. For these reasons, the detection of antibiotics has attracted extensive attention in recent years. Based on the electrochemical activity of most antibiotics, nano-modified-electrode can improve the sensitivity of electrochemical sensor by enhancing the electrochemical oxidation or reduction reaction of antibiotics in electrolyte. Various electrochemical sensors for the detection of antibiotics are described in detail in this paper, as well as their properties. Finally, the challenges and development prospects of nanomaterial electrochemical sensors in antibiotic detection are discussed.
Organic/inorganic hybrid polyimide matrix resins with high temperature resistance
LIU Yi, MO Song, XU Xiaozhou, DU Xinyu, HE Minhui, ZHAI Lei, FAN Lin
2023, 40(1): 62-71. doi: 10.13801/j.cnki.fhclxb.20220415.002
Thermosetting polyimide resin matrix composites have been widely used in aerospace industry, but the heat resistance of traditional organic polyimide matrix resins is gradually insufficient to satisfy the design and application requirement of the aircrafts, with the development of aerospace technology. Therefore, novel organic/inorganic hybrid polyimides resistant to higher temperature have become the focus of research. In this paper, the recent progress of organic/inorganic hybrid polyimide matrix resins was summarized. The synthetic pathway, structure design, performance control, curing process and degradation behavior of polyhedral oligomeric silsesquioxane-containing polyimide, carborane-containing polyimide and siloxane-containing polyimide were reviewed, providing a detailed description of the characteristics and thermo-resistant mechanism of the organic/inorganic hybrid polyimide resins. The challenges and opportunities for the future development of organic/inorganic hybrid polyimide resins were also discussed and analyzed.
Resin Polymer Composite
Mode I interlaminar fracture toughness measurement of PBO fiber reinforced epoxy composites by DIC technology
YANG Lu, XIAO Jinyou, WEN Lihua, ZHANG Chengshuang, HOU Xiao
2023, 40(1): 72-82. doi: 10.13801/j.cnki.fhclxb.20220112.002
The mode I double cantilever beam (DCB) test was commonly applied to investigate the material resistance to crack propagation in unidirectional composites, aiming at obtaining the interlaminar fracture toughness in mode I, which was an important input parameter for the study of delamination propagation and failure mechanism of composite materials. The DCB test must be suspended frequently for the multiple measurements of the crack length, which will not only have a potential effect on the propagation of crack and even lead to the measurement error, but also can be a time and effort consuming process. Digital image correlation (DIC) technology applied to crack propagation length measurement has the advantages of real-time tracking and precise positioning, effectively improving the measurement efficiency of the mode I fracture toughness, but it still has limitation when applied to discontinuous deformation behavior, and it is susceptible to interference from image noise, resulting in measurement error. This paper developed a real-time crack length detection method based on DIC and obtained the discontinuous deformation displacement field of the specimen through an image matching algorithm, and then proposed an identification method based on the degree of dispersion of the global lateral displacement, which realized the crack tip real-time capture. Then, compared with the traditional measurement method in the DCB test, the measurement error of the crack length does not exceed 2.76% on average, which verifies the accuracy and efficiency of the method, meanwhile, overcomes the measurement interference caused by roughness of the side surface, the poor speckle quality and the fiber bridging of the poly p-phenylene-2,6-benzoxazole (PBO)/epoxy composites. Finally, the effective initial value and steady-state propagation value of the mode I interlaminar fracture toughness.
Preparation and properties of high strength-medium density nanoporous resin-based ablation/insulation integrated composites
QIAN Zhen, ZHANG Hongyu, ZHANG Qikai, WANG Feng, WANG Sheng, ZHAO Jian, NIU Bo, ZHANG Yayun, LONG Donghui
2023, 40(1): 83-95. doi: 10.13801/j.cnki.fhclxb.20211223.001
To meet the extreme thermal protection requirement of new-generation spacecrafts, nanoporous resin composites (IPC-90) with medium-density, high strength and excellent ablation/insulation properties had been prepared via a sol-gel polymerization using phenolic resin as nanoporous matrix and needled fiber fabric as the reinforcement. The effects of fiber type, namely quartz fiber (QF/IPC-90) and carbon fiber (CF/IPC-90) on the microstructure, mechanical properties, static thermal insulation, and ablation properties of the composites were systematically studied. The as-prepared IPC-90 with medium density of ~0.95 g/cm3 has excellent mechanical properties with tensile strength >120 MPa and bending strength >90 MPa. Due to the introduction of nanopore resin matrix and lightweight fiber felt, the resultant IPC-90 has relatively low room-temperature thermal conductivities (0.089 W/(m∙K) for QF/IPC-90 and 0.120 W/(m∙K) for CF/IPC-90), as well as low effective thermal conductivities at 1000℃. Furthermore, the possible ablation mechanisms under different temperatures were analyzed. It is found that both QF/IPC-90 and CF/IPC-90 have low linear ablation rates under the oxygen-propane ablation test below 2000℃, which are mainly caused by resin matrix pyrolysis and shrinkage. However, under the oxy-acetylene ablation test above 2000℃, the ablation of CF/IPC-90 is dominated by ultrahigh temperature carbonation-sublimation, while the severe ablation of CF/IPC-90 is caused by the melting of quartz fiber. Under the oxy-acetylene ablation of 4.2 MW/m2, the linear ablation rates of CF/IPC-90 and QF/IPC-90 are 0.073 mm/s and 0.186 mm/s, respectively, being similar to the conventional high-density phenolic composites.
Effect of thermo-oxidative aging on the mechanical properties of multi-layered biaxial weft knitted fabric reinforced composites
YANG Chen, JIANG Yaming, XIANG He, LI Jia’nan
2023, 40(1): 96-108. doi: 10.13801/j.cnki.fhclxb.20220225.002
Several multilayered biaxial weft knitted (MBWK) fabric reinforced composites with different shear angles were prepared by changing the orientation of preform inserting yarns. The thermo-oxidative aging test was designed based on Arrhenius model and Ozawa method. The thermal and physical properties of the samples before and after aging were characterized by mechanical properties, DSC, FTIR and DMA tests. The experimental results show that: With the change of yarns’ shearing angle, the composite mechanical properties retention rate after thermo-oxidative aging is also significantly different, because the post curing will occur for the vinyl ester resin in the thermo-oxidative aging environment. Therefore, the bending modulus of the composite materials in the aging process presents downward trend after increased first, and the tensile properties are affected by the reinforcement structure. The degradation of adhesion strength at fiber/matrix interface makes the tensile modulus decrease continuously during the aging process. With the aging time prolongation, the curing degree of resin increases gradually, and the glass transition temperature Tg increases gradually. The peak value of energy storage modulus increases at the initial stage of aging due to molecular chain crosslinking, while decreasing of the peak value is caused by molecular chain fracture at the later stage of aging.
Comparision of vibration fatigue behaviors of 2.5D woven composites in warp and weft directions
WANG Yana, REN Sue, ZHANG Qin, LIU Yanfeng, HE Yuhuai
2023, 40(1): 109-118. doi: 10.13801/j.cnki.fhclxb.20220223.001
2.5D woven composites are resistant to delamination and impact, which have great application prospects in aeroengine structures. The first-order bending vibration fatigue tests under different stress levels were carried out for the specimens made of 2.5D woven carbon fiber reinforced bismaleimide resin matrix composites in the warp direction and weft direction, respectively. The experimental results show that the vibration fatigue performance of the warp specimens is better than that of the weft specimens. With the increase of stress levels, the lives of the specimens are shortened obviously, and the decline percentage of natural frequency increase, and the damage degree and damage propagation speed within specimens also increase. In the process of vibration fatigue test, the main failure mode of 2.5D woven composites was the loss of structural integrity caused by the debonding of the yarns and the matrixes, which leaded to the continuous decrease of the stiffness of the specimens. 3D CT reconstruction images of the internal damage of the specimens show that the damages spread throughout in the working section of the specimens. The higher the stress levels are, the greater the internal damage ranges and the higher the damage degrees are. And the internal damage state of the warp specimens is more serious than that of the weft specimens. The mathematical model of stress-life (S-N) curve of vibration fatigue of 2.5D woven composites is obtained by data fitting for vibration fatigue results under different nominal stress levels by using the log-log-linear life model, which can be used to predict the life of 2.5D woven composites.
Tensile mechanical behavior of ultra-high molecular weight polyethylene reinforced thermoplastic resin matrix composites for ballistic application
HE Yemao, JIAO Yanan, ZHOU Qing, JIA Nan, CHEN Li, WAN Xili
2023, 40(1): 119-130. doi: 10.13801/j.cnki.fhclxb.20220221.001
Ultra-high molecular weight polyethylene (UHMWPE) fiber reinforced thermoplastic resin matrix composites for ballistic application were selected as the research object. Composite laminates with unidirectional orthogonal structure were prepared by hot pressing process. Based on the self-designed tensile test device, the in-plane tensile tests of UHMWPE fiber reinforced thermoplastic resin matrix composite on macro and quasi meso scales were carried out to investigate its in-plane tensile mechanical properties and failure modes. The results show that the in-plane tensile mechanical properties of UHMWPE composites for ballistic application on quasi meso scale are their intrinsic properties. With the increase of off-axis angle, the tensile fracture strength decreases exponentially. This is attributed to the failure mode changing from the tensile fracture failure of fiber to the interfacial failure between the fiber and resin matrix. Furthermore, the tensile failure strength of UHMWPE fiber reinforced thermoplastic resin matrix composites on the macro scale is 50.52% lower than that on the quasi-meso scale, because the in-plane tensile mechanical response on the macro scale is the coupling result of in-plane tensile deformation and interlayer delamination failure, that is, the lamination effect of laminates.
Preparation of polyimides containing carborane moiety and the thermal resistance mechanism
HAO Yifan, DONG Jie, ZHAO Xin, ZHANG Qinghua
2023, 40(1): 131-140. doi: 10.13801/j.cnki.fhclxb.20220124.001
A series of polyimide materials were successfully prepared by embedding o-carborane cage structure into polyimide main chains. First, the diamine monomer (DNCB) containing o-carborane unit was designed and synthesized, and then copolymerized with 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-benzophenone tetracarboxylic anhydride (BTDA) to synthesize the polyamic acid (PAA) precursor solution. PAA films were prepared by solution casting method, and then polyimide films containing different contents of carborane unit were obtained after high-temperature thermal imidization. Thermogravimetric analysis (TGA) shows that the addition of DNCB significantly improves the thermal stability and thermal oxidation stability of polyimide materials. When the molar content of DNCB in all diamines reaches 40%, the temperature corresponding to 5wt% mass loss (T5%) increases by nearly 13℃, T10% increases by nearly 43℃ and the mass residual rate was as high as 82.6wt%. Under the air atmosphere, T5% increases by nearly 36℃, T10% increases by nearly 64℃, and the mass residual rate reaches as high as 83.1wt%. This is due to the oxidation of carborane cage and the formation of multi-layer passivation protective layer on the surface of the film, which prevents the degradation of internal polymer materials in contact with oxygen.
Formation mechanism of drilling defects on CFRP pipe surface
QIU Xinyi, LI Pengnan, NIU Qiulin, LI Shujian, LI Changping, TANG Lingyan
2023, 40(1): 141-150. doi: 10.13801/j.cnki.fhclxb.20220315.001
Carbon fiber reinforced polymer (CFRP) drive shaft is widely used in lightweight fields such as automobile, aerospace, ship and cooling tower fan because of its excellent performance, but it is prone to burr, delamination and other defects in the drilling process. In order to reveal the formation mechanism of defects in CFRP pipe surface drilling, double point angle drills and candle stick drills were selected to drill CFRP pipe surface. Using the method of drilling blind holes and through holes by some steps, the force of the damaged part was analyzed to study the causes of hole entry tear, hole exit burr and delamination. According to the experimental results, it is found that the hole entry tear of the double point angle drill is large. The tear damage is located at the lowest point of the contact between the drill bit and the pipe surface, and it is mainly the fibers that are horizontally wound around the CFRP pipe. The reason is that the horizontally wound fibers have the largest buckling deformation and are more sensitive to the cutting force. The chisel edge of double point angle drill and candle stick drill had no effect on the final delamination of the hole, and the cutting action of the main cutting edge determined the hole final exit delamination. For using the same drill, the axial force is not the only factor affecting the delamination factor, and the cutting heat should also be considered. Compared with the double point angle drill, the candle stick drill can effectively cut the fiber due to the sharp outer corner edge, making smaller hole exit delamination.
Thermal reaction characteristics of large tow PAN precursors and their evolution of structure and properties during continuous pre-oxidation
CHEN Xiaohan, GUO Lichuang, HUANG Xiangyu, WANG Xiaoxu, LIU Jie, WANG Chunhua
2023, 40(1): 151-159. doi: 10.13801/j.cnki.fhclxb.20220225.001
Thermal stress, DSC, FTIR, element analysis (EA), XRD, mechanical properties and density were used to analyze the thermal reaction characteristics of large tow polyacrylonitrile (PAN) precursors (48K) in combination with small tow PAN precursors (24K). The large tow carbon fibers were prepared by 50 min continuous pre-oxidation method, in which the evolution of structure and properties were studied. The results show that the thermal stress of large tow PAN precursors is 1.13-1.43 times of small tow PAN precursors, and the starting temperature is lower. The difference of thermal stress reaches maximum at 250℃ and the corresponding density of large tow fibers is 1.316 g/cm3. The crystal regions of PAN precursors transform into amorphous regions rapidly at the initial stage of reaction, and the grain size of the crystal regions increases first and then decreases. The monofilament tensile strength and modulus of large tow carbon fibers prepared by 50 min continuous pre-oxidation are 4240 MPa and 244 GPa, respectively, which are at the same level as those commercial foreign large tow carbon fibers.
Thermal conduction mechanism and heat dissipation effect of compression molded boron nitride/polyethylene terephthalate composites
WANG Shimin, WEN Bianying
2023, 40(1): 160-170. doi: 10.13801/j.cnki.fhclxb.20211215.002
The high density integration of components in electronic and electrical equipment makes the problem of heat dissipation increasingly prominent, and the demand for thermal conductive materials is increasing. In this paper, polyethylene terephthalate (PET) and hexagonal boron nitride (h-BN) were used as the matrix and thermally conductive filler, respectively, a series of h-BN/PET composites were prepared by melt blending method. The effect of the h-BN content and the crystallinity of the PET matrix on the thermal conductivity of the composites were investigated, and the thermal conduction mechanism of the composites was analyzed. The temperature dependence of the thermal conductivity and heat dissipation effect of the composites were explored from the perspective of material application. The results show that both the crystallinity of the PET matrix and the content of h-BN both contribute to the final thermal conductivity of the composites, and the thermal conductivity of the composites increases with the increase of the crystallinity and h-BN content. h-BN plays a role of heterogeneous nucleation, significantly accelerates the crystallization rate of PET and improves the crystallinity of PET. In compression molding, h-BN is driven by shear stress to oriented in the direction of flow in the PET matrix, resulting in the composite material showing obvious anisotropic characteristics. The orderly arrangement of h-BN in the in-plane direction provides more channels for phonons transmission. When the filling amount of h-BN reaches to 50wt%, the in-plane and through-plane thermal conductivity of the composites reach the maximum values of 3.00 W·(m·K)−1 and 2.19 W·(m·K)−1, respectively. h-BN/PET composites have good heat dissipation effect. The higher the h-BN content, the faster the cooling rate. The rule of temperature drop conforms to the exponential function during the heat dissipation process.
Functional Composite
Supercritical CO2 fluid assisted synthesis of Si-Fe-Fe3O4-C composites and lithium storage performance
LU Zhihang, MA Junkai, YANG Gangfeng, XIA Yang, GAN Yongping, ZHANG Jun, ZHANG Wenkui, HUANG Hui
2023, 40(1): 171-179. doi: 10.13801/j.cnki.fhclxb.20220126.003
Silicon-carbon anode is an important issue for the development of lithium-ion battery materials. Aiming at the problems of uneven combination and poor interfacial contact of silicon-carbon anode prepared by traditional ball milling, this paper proposes a new strategy to synthesize Si-Fe-Fe3O4-C composite by ball milling in supercritical carbon dioxide (scCO2) fluid medium. It is found that during the process of ball milling mixture of nano-silicon and mesophase carbon microspheres (MCMB) in the scCO2 medium, CO2 and Fe reacts firstly to form a uniformly dispersed Si-FeCO3-C precursor, and then in situ high temperature decomposition of FeCO3 solid phase results in final Si-Fe-Fe3O4-C product. Under the infiltration of scCO2 fluid, MCMB microspheres exfoliate into graphite flakes, and achieve ideal combination with nano-silicon and Fe-Fe3O4. The introduction of Fe-Fe3O4 in the composite has significantly improved the lithium storage capacity, cycle stability and rate performance of silicon-carbon anode, the synthesized Si-Fe-Fe3O4-C composite material maintains a reversible capacity of 1065 mA·h·g−1 after 100 cycles at 0.2 A·g−1. The method shows the merits of facile operation procedure, easy industrial production and potential commercial application basing on the supercritical fluid permeability and strong diffusion ability.
Preparation and adsorption-photocatalytic properties of Cu2O-PVA/nanocellulose composite
WANG Yanfei, JIN Zeyuan, LI Zhuolin, WANG Heran, XING Pengyu, LUO Linlong, HU Yingcheng
2023, 40(1): 180-191. doi: 10.13801/j.cnki.fhclxb.20220117.004
In order to improve the photocatalytic performance of cuprous oxide (Cu2O), Cu2O particles and polyvinyl alcohol (PVA) were added to nanocellulose (CNF) at the same time, and a functionalized cellulose-based aerogel (Cu2O-PVA/CNF) with three-dimensional (3D) porous structure and abundant active sites were successfully prepared by the exsitu method. The aerogel samples were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffractometer, automatic specific surface area, and compression test. Taking the degradation of methylene blue (MB) as a model pollutant, the photocatalytic performance of 6wt%Cu2O-PVA/CNF composite catalyst was evaluated, the effects of different initial concentrations, catalyst dosages and solution pH conditions on the photodegradation of MB were investigated. The results show that the use of the three-dimensional porous cellulose aerogel improves the adsorption capacity of MB and prolongs the absorption of visible light. In particular, Cu2O doped in the cellulose matrix excites electron-holes under light, which increases the active sites, thereby improving the catalytic ability. The photodegradation rate of 6wt%Cu2O-PVA/CNF composite catalyst to MB reaches 95.6%, which is much higher than 79.6% of pure Cu2O. The photodegradation process of Cu2O-PVA/CNF composite catalyst follows the apparent quasi-first order dynamics model. In addition, compared with pure CNF aerogel, the addition of PVA increases its compressive strength by 4.4 times. The catalyst is reused after 5 photocatalytic cycles, and the visible light catalytic degradation rate of MB can still reach 71.06%. The Cu2O-PVA/CNF composite material is beneficial to the treatment of dye wastewater by solar radiation.
Hard@soft composite carbon anodes towards synergistic potassium storage
CHEN Yaxin, CAI Yaling, CAO Zhenjiang, GAN Mingtao, GUO Nannan, JU Zhicheng
2023, 40(1): 192-200. doi: 10.13801/j.cnki.fhclxb.20220214.003
Hard@soft composite carbon can improve the potassium storage performance synergistically by combining the advantage of hard carbon and soft carbon. But the potassium storage mechanism of different composite structure is lack. Here, rhodanine and F127 were used as the precursor of hard carbon, and the volatile matter of coal tar pitch was used as the precursor of soft carbon. Hard carbon, soft/hard hybrid carbon and soft carbon shell@hard carbon core composite were fabricated using co-carbonization and chemical vapor deposition. When used as the anode materials of potassium-ion battery, soft carbon shell@hard carbon core composite possesses high reversible capacity (365 mA·h·g−1 at 0.05 A·g−1), high cyclic stability (80% after 100 cycles), and excellent rate performance (177 mA·h·g−1 at 1 A·g−1). It can be ascribed to the abundance of active sites of hard carbon and the coating of soft carbon on the defect sites at the surface of hard carbon. Moreover, the soft carbon can improve the conductivity of the composite, which can enhance the rate performance of composite anode and release the voltage hysteresis. Benefiting from the synergistic potassium storage, soft carbon shell@hard carbon core composite anode shows much better performance than hard carbon anode.
Preparation of BiOI/BiOBr0.9I0.1 photocatalyst and its degradation performance on 2,4-dichlorophenoxyacetic acid
YU Guanlong, WANG Shitao, YANG Kai, SUN Qifang, YANG Yi
2023, 40(1): 201-211. doi: 10.13801/j.cnki.fhclxb.20220216.001
The pollution of pesticides seriously threatens the ecological environment and drinking water safety. A novel and efficient photocatalyst of BiOI/BiOBr0.9I0.1 was prepared through solvothermal method. The physicochemical properties, such as structure, morphology and optical properties, were characterized by detections of XRD, SEM, XPS, UV-vis DRS, PL, EIS, etc. The BiOI/BiOBr0.9I0.1 synthesized has a cluster-like accumulation structure, which facilitates the increase of active sites. The combination of solid solution and heterojunction broadens the photoresponse range of BiOBr, effectively prevents the recombination of photogenerated electron-hole pairs inside BiOI/BiOBr0.9I0.1 and improves the redox ability of photogenerated carriers. The results of photocatalytic experiments show that 15wt%BiOI/BiOBr0.9I0.1 reaches the best photocatalytic performance for 2,4-dichlorophenoxyacetic acid (2,4-D) under visible light, and the degradation efficiency of 2,4-D can reach 95% within 120 min. Furthermore, the degradation rate still reaches 80.9% after four cycles of experiments. According to the results of capture experiments and electron spin-resonance (ESR) tests, it can be confirmed that •O2 and h+ are the main active species. The BiOBr0.9I0.1 synthesized can effectively modulate the energy band structure of BiOBr. The heterojunction composed of BiOBr0.9I0.1 and BiOI is consistent with the characteristics of Z-scheme heterojunction, and the synergistic effect between the two strategies of constructing heterojunction and solid solution can be produced in enhancing the photocatalytic activity of BiOBr.
Preparation and properties of regenerated polyester hollow fiber wikis for sound absorption
XIANG Yulong, GUO Jing, GUAN Fucheng, LI Feng, YANG Qiang, DI Chunqiu
2023, 40(1): 212-218. doi: 10.13801/j.cnki.fhclxb.20220225.004
With the aggravation of environmental pollution, the development and application of recycled polyester fibers based on bottle chip is of great significance. In this paper, recycled polyester hollow fibers and skin core type heat-bonded fibers were used as raw materials to prepare sound absorbing materials with multi-scale micropores by hot air consolidation. The structure and properties of polyester hollow fibers were characterized. Standing wave tube method was used to study the relationship between linear density and sound absorbing effect of hollow fibers, and a "multistage" sound absorbing theory was proposed. The results show that the hollow fibers with the linear density of 10 D has the largest hollowness, the best toughness and the best sound absorption effect. The sound absorption coefficient and noise reduction coefficient increase linearly with the increase of thickness. When the thickness is 2 cm, the noise reduction coefficient (NRC) is greater than 0.5, which is expected to become an ideal sound absorption material.
Preparation of magnetic Fe3O4 nanocomposites and their adsorption to Pb(II)
BAO Guoqing, WU Chunxin, ZHAO Deming
2023, 40(1): 219-231. doi: 10.13801/j.cnki.fhclxb.20220117.001
In order to solve the problem that Fe3O4 nanoparticles were easy to be corroded and agglomerated, it was decided to functionalize it. Magnetic nano-Fe3O4 particles were prepared under ultrasonic irradiation, then 2-diaminobenzenesulfonic acid (SP) and m-phenylenediamine (mPD) monomers were selected as introduction agents to prepare metal matrix composites Fe3O4-mPD/SP(95∶5), which were rich in amino, sulfonic acid and imine active functional groups, and nanocomposites were characterized by FTIR, TEM, XRD and other methods. The characterized results show that the magnetic nanocomposites prepared by ultrasonic strengthening method have the characteristics of good stability, high reaction activity, small particle size and larger specific surface area. The adsorption properties of Pb(II) by Fe3O4-mPD/SP were investigated which showed that the molar percentage of SP and mPD, reaction temperature, sorts of competitive cations and the pH value of solution all had effect on the adsorption of Pb(II). The adsorption isotherm conforms to the Freundlich model, and the adsorption of Pb(II) is a spontaneous process, Gibbs free energy ∆G0<0. It is found that the adsorption behavior of Pb(II) on nanocomposites can be well described by quasi secondary dynamics equation, kinetic constant k2=3.61×10−3 g·mg−1·min−1, equilibrium adsorption capacity qe=63.297 mg·g−1. It is speculated that the adsorption mechanism of this adsorbent includes ion exchange, complex adsorption and electrostatic adsorption.
Experimental analysis and theoretical prediction to piezoresistance sensing characteristics of multiwalled carbon nanotubes/natural rubber composite
LIU Xingyao, GUO Rongxin, YANG Yang, FAN Zhengming, WANG Yang
2023, 40(1): 232-243. doi: 10.13801/j.cnki.fhclxb.20220120.007
A multiwalled carbon nanotubes (MWCNT)/natural rubber (NR) composite was prepared by two-roll method to achieve effective monitoring for the working performance of isolation bearings. The resistance-strain response behaviors of MWCNT/NR composites under constant strain and interval loading were studied. The results show that the stability, repeatability, monotonicity, symmetry and ‘shoulder peak’ effect of the resistance-strain response are depended on the constant strain loading. The variation amplitude of resistance tends to be stable with the increase of interval time, and the change of the amplitude can effectively be predicted via the theoretical model established. The piezoresistance behaviors for MWCNT/NR composite under different delamination forms show distinct characteristic, and the response mechanism is explained by Digimat and Workbench. A mathematical model that can completely characterize and predict the dynamic resistance-strain response was established and verified based on viscoelasticity of NR and conductivity network of MWCNT. The analytical results obtained by mathematical model are in good agreement with the experimental results, which lay a theoretical foundation for the industrial application of MWCNT/NR composites.
Fabrication of superhydrophobic FeNi2O4/vinyl methacrylate-diethylenebenzene copolymer porous material and its application for oil-water separation
YU Chuanming, QIU Xinni, WANG Xin, ZHANG Nantao, HUANG Keyi, KE Siyin, LI Yong
2023, 40(1): 244-254. doi: 10.13801/j.cnki.fhclxb.20220120.005
To cope with the increasing frequency of oil spills and to achieve the purification of oily waters, FeNi2O4−doped vinyl methacrylate-diethylenebenzene copolymer porous materials were fabricated via a high-internal-phase Pickering emulsion templating method. The material structure was characterised using FTIR, SEM, TGA, VSM, contact angle measurement, static mercury piezometry and universal testing machine. The results show that the material possesses a three-dimensional porous structure with pore sizes mainly distributed at 3 μm and 6-14 μm, and the large pore size can be modified. The material demonstrates good thermal stability with an initial thermal decomposition temperature of up to 300℃. The introduction of FeNi2O4 nanoparticles not only enhances the emulsion stability but also imparts magnetic responsiveness to the material. The materials exhibit good hydrophobicity and lipophilicity, with water contact angle of 151°, rolling angle of 5° and oil contact angle of 0°, fast oil absorption rate, good reusability and excellent oil-water adsorption selectivity. Its saturation adsorption multiplicity for a variety of oils and organic solvents reaches 40.80-93.08 g·g−1, and the oil retention rate are all above 90%. The pore structure regulation of the material was investigated and it was found that changing the internal comparison of the emulsion could regulate the macropore distribution, porosity, density, specific surface area, oil adsorption multiplicity and mechanical property of the material. In summary, superhydrophobic FeNi2O4/vinyl methacrylate-diethylenebenzene copolymer porous materials can efficiently separate oil from water, which is of practical significance for the treatment and purification of the aqueous environment.
Study of the degradation of tetracycline by visible photo-Fenton catalyzed by ultrasound-assisted LaFeO3/PS
GE Xiaodong, MENG Guanhua, LIU Baohe, ZHANG Linsen, YANG Jianhua, CHENG Luowen
2023, 40(1): 255-269. doi: 10.13801/j.cnki.fhclxb.20220101.001
The powdered LaFeO3 material had shortcomings such as easy agglomeration and difficult separation, so it was limited in large-scale applications. The deposition of powdered catalysts in polystyrene resin (PS) made up for the above shortcomings of powdered materials. Therefore, in this study, the self-assembled LaFeO3 gel was deposited on the PS through ultrasound-assisted sol-gel and hydrothermal methods. The dispersion and distribution of LaFeO3 on PS broadens the forbidden band width of LaFeO3, improves its redox ability, solves the problem of agglomeration, and consequently improves its photo-Fenton catalytic activity. The LaFeO3/PS composite prepared under the following experimental conditions shows the highest photocatalytic activity: La∶Fe∶Citric acid(CA) molar ratio=1∶1∶2, ultrasonic time 40 min, hydrothermal temperature 90℃, hydrothermal time 18 h, LaFeO3 initiator/polystyrene mass ratio=32∶1. The removal rate of tetracycline hydrochloride (TC) is up to 96.51%(rate of degradation k=0.0160 min−1) under visible light irradiation in the Fenton process catalyzed by LaFeO3/PS. Free radical capture experiments show that •O2 is the main active species. According to the capture experiment, the degradation mechanism of TC was proposed. Through LC/MS analysis, the degradation path of TC was obtained. The photo-Fenton process catalyzed by LaFeO3/PS is a promising technology for the degradation of organic pollutants due to the high stability of the catalyst and the efficient use of solar energy.
Preparation and CO2 adsorption properties of tannin modified phenolic based carbon cryogels
ZHOU Yalan, LUO Lu, FAN Mizi, DU Guanben, ZHAO Weigang
2023, 40(1): 270-279. doi: 10.13801/j.cnki.fhclxb.20220110.002
Based on the large number of reactive hydroxyl of green and low cost of tannin, its hold the similar mechanism as phenol and resorcinol reacted with formaldehyde. On the basis of carbon cryogels from traditional phenolic resin (phenol-urea-formaldehyde), a new type of carbon cryogels for efficient CO2 capture were successfully prepared by tannin modification. The surface chemistry and pore structure of carbon aerogel were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption and desorption analysis. The adsorption capacity, selectivity and adsorption heat of carbon cryogel were studied by carbon dioxide adsorption and desorption analysis. The results show that the new and efficient phenolic carbon cryogel can be prepared by using green and renewable biomass raw material tannin to partially replace the traditional phenol or resorcinol, which can not only significantly reduce the product cost, but also significantly improve the carbon dioxide adsorption performance. When the addition amount of tannin (15 g) is 50wt% of that of phenol, the sample has the maximum specific surface area (1376.31 m2·g−1) and micropore volume (0.55 cm3·g−1), which is a potential gas adsorption material. The corresponding CO2 adsorption capacity is as high as 5.36 mmol·g−1, and the selective adsorption and adsorption heat are 16.84 and 34.49 kJ·mol−1, respectively. The properties of phenolic carbon aerogels are significantly better than those of unmodified phenolic carbon aerogels, and also better than most of the traditional carbon aerogels. This is mainly attributed to its high specific surface area, micropore volume, suitable pore size distribution and good 3D network structure.
Arc erosion resistance of Cu-Al2O3 composite effected by CNTs
YANG Yubo, GUO Xiuhua, SONG Kexing, LI Shaolin, MI Xujun, LI Zhou
2023, 40(1): 280-289. doi: 10.13801/j.cnki.fhclxb.20220112.001
Cu-Al2O3 composite has excellent conductivity and mechanical properties, and it widely used in the field of wear-resistant materials. In order to further improve the arc erosion resistance of composite under the condition of electro-friction, CNTs/Cu-Al2O3 composites with different contents of carbon nanotubes (CNTs) were prepared by internal oxidation combining with powder metallurgy. The distribution of reinforcing phase and the interface between CNTs and matrix in CNTs/Cu-Al2O3 composites were observed. The conductivity and mechanical properties of Cu-Al2O3 composites effected by CNTs were studied. The arc erosion resistance mechanism of CNTs/Cu-Al2O3 composites was mainly explored. The results show that in-situ nano-Al2O3 particles pin dislocation, CNTs are dispersed in the copper matrix due to the regulation of CNTs distribution by Al2O3 particles. Compared with Cu-Al2O3 composites, the arc duration and energy of CNTs/Cu-Al2O3 composites are obviously reduced and fluctuate more stable. In the process of arc erosion, CNTs in the molten pool will float to the surface to disperse the arc and reduce the concentrated erosion area. Nano-Al2O3 particles can stabilize the molten pool, reduce the splash of molten droplets and the mass loss of CNTs/Cu-Al2O3 composites. Among them, CNTs/Cu-3.5Al2O3 composites with 1.2vol%CNTs has the lowest and most stable arc duration and energy. This research result provides a favorable theoretical basis for the research of ablation resistant materials.
Fabrication and optimization of dielectric elastomer actuator using MWCNT-CB/PDMS composite electrodes
MA Li, DING Jingxian, ZHANG Xiaodie, SHEN Linawa, PAN Jiuhong, GUO Dongjie
2023, 40(1): 290-299. doi: 10.13801/j.cnki.fhclxb.20220124.003
Flexible electrode of dielectric elastomer actuator (DEA) plays important roles in generating electric fields and constraining dielectric matrix deformation. By using one-dimensional multi-wall carbon nanotubes (MWCNT) and zero-dimensional conductive carbon black (CB) as co-conductive fillers, a series of polydimethyl siloxane (PDMS) composite electrode films (MWCNT-CB/PDMS) were designed with varying size, mechanical and electrical properties. The electrode films were adhered to the lateral surfaces of a polyvinyl chloride gel matrix film and imported into a pulsed high-voltage signal to obtain novel dielectric polymer actuators with various electromechanical behaviors. Tests of electromechanical properties reveal that, the increase of electrode coverage is beneficial to DEA’s strain, the increase of electrode thickness hampers its strain, while the strain exhibits an initial increase following decrease trend with increasing MWCNT loading. Orthogonal experiments show that, the MWCNT loading has a significant effect on the displacement output, while the electrode coverage and thickness present high-level significances to the displacement output. Under the optimal condition, the displacement output of DEA is 1.71 mm at maximum.
Preparation and properties of sodium nitrate/semi-coke ash shape-stable phase change composite
YAO Chenhua, XIONG Yaxuan, REN Jing, SONG Chaoyu, WANG Huixiang, DING Yulong
2023, 40(1): 300-309. doi: 10.13801/j.cnki.fhclxb.20220222.002
The massive accumulation of industrial solid waste semi-coke ash (SCA) will cause damage to local ecological environment. To promote the large-scale consumption of industrial solid waste semi-coke ash and fabricate low-cost shape-stable phase change composites (SSPCCs), semi-coke ash was innovatively proposed as a skeleton material to fabricate the SSPCCs. To evaluate the feasibility of the semi-coke ash as the skeleton material of the SSPCCs, eight NaNO3/semi-coke ash SSPCC samples with different mass ratio of the semi-coke ash to NaNO3 were fabricated. The key performance of the NaNO3/semi-coke ash SSPCCs were investigated by the differential scanning calorimetry, laser flash analysis, scanning electron microscopy, constant speed pressurization method and X-ray diffraction. Results show that the sample NaNO3/SCA-50 without visual leakage and deformation holds the optimal mass ratio 5:5 of the semi-coke ash to NaNO3 with the thermal energy storage capacity of 338.24 J/g ranging from 100 to 380℃ and the mechanical strength of 96.98 MPa. After 4027 heating/cooling cycles, the sample NaNO3/SCA-50 keeps good thermal stability and chemical compatibility, which indicates that the semi-coke ash is feasible for the SSPCCs fabrication, and provides a new way for recycling the resource of the solid waste semi-coke ash.
Form-stabilized phase change composites based on biochar and n-Eicosane for photo- and electro-thermal conversion and heat storage
YU Xinghai, LI Yan’an, TANG Haiwei, HAN Yuqi, WANG Yongsheng
2023, 40(1): 310-322. doi: 10.13801/j.cnki.fhclxb.20220223.002
To overcome the obstacles of poor thermal conductivity of pure n-Eicosane, a typical single-phase change material, and prevent the melt from leaking during the phase change process, a biochar/n-Eicosane based composite phase change material that possesses high form stabilization, photo- and electric-thermal converting, and enhanced phase change heat transfer was prepared. Firstly, corn straw was selected as the raw material of biomass, and pyrolyzed at higher temperature. Following a KOH etching procedure at 700℃, a biochar support with large surface area and hierarchically interconnected pores were obtained. Then, KBC/n-Eicosane composite phase change materials were prepared by injecting n-Eicosane into biochar skeletons via ethanol melting and vacuum impregnation. The as-prepared composite materials were characterized by SEM, XRD, FTIR and other characterization methods. The thermal stability and heat storage capacity were also tested by TG and DSC. The effect of mass content of n-Eicosane to melting enthalpy and crystallization enthalpy were calculated, and the results reveal that the optimized mass content is mKBCmn-Eicosane=1∶2 associated with the melting enthalpy and crystallization enthalpy of 121.3 J·g−1 and 117.6 J·g−1, respectively. Notably, after 100 thermal cycles, the melting enthalpy and crystallization enthalpy have negligible changes, and no clear liquid leaking is observed through all thermal cycles, indicating significant thermal storage ability and cycling stability. In addition, the ability of photo- and electro-thermal conversion and storage of the composite phase charge materials were tested by simulated sunlight irradiating and DC power supply powering. The results display that the KBC/n-Eicosane composite phase materials are capable of converting solar energy or electric energy into thermal energy and storing as latent heat with excellent performance. Thus, the as-prepared KBC/n-Eicosane are not merely a phase charge materials with remarkable properties, but can realize varied energy transformation and storage, showing great potential for use in green and renewable energy conversion and storage.
g-C3N4/BiOCl composite photocatalyst used as 2D/2D heterojunction for photocatalytic degradation of dyes
WU Jianbo, SHI Liang, ZHENG Xiaoqiang, ZHANG Mingjian, CHEN Lijuan
2023, 40(1): 323-333. doi: 10.13801/j.cnki.fhclxb.20220225.006
In order to expand the sunlight absorption range of BiOCl and obtain more efficient photocatalyst, Graphite phase carbon nitride (g-C3N4)/BiOCl (2D/2D) composite photocatalyst was prepared by hydrothermal method and characterized in detail. The results of structural and morphology characterization show that BiOCl nanosheets are deposited on the layered g-C3N4 surface to form 2D/2D face-face composite structure. The analysis of photoelectric chemical properties shows that the formation of heterostructure can effectively expand the frequency range of light absorption and promote the separation and migration of photocarriers, which is conducive to the improvement of photocatalytic performance. The results of photocatalytic degradation of RhB by xenon lamp (500 W) show that the photocatalytic degradation activity of g-C3N4/BiOCl heterojunction is much higher than that of g-C3N4 and BiOCl alone. Among them, 9wt%g-C3N4/BiOCl shows the most superior photocatalytic activity, and the degradation rate of RhB is 94% within 180 min, and the apparent rate constant Kapp value of 9wt%g-C3N4/BiOCl is 5.7 and 3.6 times that of g-C3N4 and BiOCl. At the same time, the photocatalytic mechanism of g-C3N4/BiOCl heterojunction was studied, and the photocatalytic degradation mechanism of RhB under dye sensitization was proposed by combining the electronic structure of the composite catalyst and free radical capture experiment.
Fabrication of high and low adhesive superhydrophobic coatings with magnesium oxysulfate whiskers and SiO2 nanoparticles
WU Peng, NAI Xueying, LIU Xin, DONG Yaping, LI Wu
2023, 40(1): 334-341. doi: 10.13801/j.cnki.fhclxb.20220303.003
Superhydrophobic materials have been received extensive attention due to their unique properties and wide applications. In this work, two kinds of superhydrophobic coatings were successfully fabricated with magnesium oxysulfate whiskers (MOSWs) and nano-silica. Firstly, surface modifications for MOSWs and nano-silica (with size of 50 nm and 500 nm) were carried out to reduce their surface energy. Then, surface roughness was constructed by mixing MOSWs and nano-silica based on a mixture design approach, which was studied using contact angle, sliding angle and average roughness (Ra) as response variables to illustrate causality among morphology, size and mixing ratio. Furthermore, the adhesive property of superhydrophobic coatings to water droplets was illustrated. The influences of roughness on superhydrophobic properties were investigated in detail. Based on the obtained results, superhydrophobic coatings with different adhesive properties were fabricated. The results show that the high adhesive superhydrophobic coating can be obtained using MOSWs as the raw material, whose contact angle is about 152.59°, and water droplets do not drip when the coating is turned upside down. The low adhesive superhydrophobic coating can be prepared by mixing MOSWs and 50 nm silica with the same mass fraction, whose contact angle and sliding angle are about 163.25° and 0°, respectively. Importantly, the excellent properties can be obtained for the low adhesive coating, when the average roughness (Ra) is between 5-10 μm.
Impact of Fe content of coal fly ash magnetospheres and the grinding size upon microstructure and microwave absorption properties of Fe3C@C-CNTs nanocomposites
ZHU Pei, ZHANG Xiaomin, YU Jie, YANG Shuang, CHEN Tianxing, HE Panyang
2023, 40(1): 342-354. doi: 10.13801/j.cnki.fhclxb.20220307.001
Nano-structured iron/carbon composites can be prepared by chemical vapor deposition (CVD) using coal fly ash magnetospheres as raw materials, showing good microwave absorption properties. However, there are problems such as uneven properties of magnetospheres and difficulty in structural regulation. In this paper, the magnetospheres were separated by the shaking bed method, and then were grinded. The effects of the magnetospheres Fe content and the grinding particle size on the CVD products were investigated. The results show that the CVD product of Fe-rich magnetospheres is Fe3C@C-CNTs, and the composite exhibits a porous cluster spherical structure. With the increase of magnetic bead Fe content, the relative carbon deposition (C/Fe value) of the composite decreases, and the graphitization degree decreases (Higher D/G peak intensity ratio ID/IG value increases), resulting in the increase of impedance matching value and the improvement of wave absorption performance. When the Fe content is 71.43wt%, the effective absorption band of the composite reaches 4.5 GHz, and the minimum reflection loss (RLmin) reaches −16.1 dB. After grinding the magnetospheres, the C/Fe value of CVD products is unchanged, but the carbon deposition rate increases, the ID/IG value increases, and the electromagnetic wave attenuation constant decreases, but the impedance matching is significantly improved, and the microwave absorption performance is greatly improved. When the grinding particle size is 18.23 μm, the effective absorption band of the composite is 4.8 GHz, and the RLmin can reach −34.7 dB. The excellent microwave absorption properties of the composites benefit from the synergistic absorption of CNTs and Fe3C@C. Multiple reflections of microwave are supposed to be enhances in the porous cluster aggregated spheres, and the promoted interface polarization is also attributed to the excellent microwave absorption properties.
Civil Construction Composite
Effect of temperature on dynamic compression properties of PVA/ECC
LIU Zejun, WANG Changye, LI Yan, ZHANG Wenbin
2023, 40(1): 355-368. doi: 10.13801/j.cnki.fhclxb.20220322.001
In order to study the effects of different temperatures, different polyvinyl alcohol (PVA) fiber contents by volume and different strain rates on the dynamic compressive properties of engineered fiber reinforced cementitious composite (PVA/ECC), impact compression tests were conducted on PVA/ECC after the high-temperature and water-cooled by using a 50 mm diameter split Hopkinson compression bar (SHPB). The results show that when the temperature is greater than or equal to 250℃, the integrity of PVA/ECC specimens becomes worse after impact damage and the stress-strain curves tend to be flatter. The dynamic peak strain doesn’t increase obviously but the dynamic peak stress and impact toughness decrease remarkably. Furthermore, the deterioration effect of high temperature on the dynamic peak stress and impact toughness of PVA/ECC with larger fiber contents by volume is more obvious. When the temperature is less than or equal to 150℃, the dynamic peak stress, peak strain and impact toughness of PVA/ECC improve significantly with increasing the PVA fiber contents by volume. When the temperature is greater than or equal to 250 ℃, the dynamic peak strain increases with increasing the PVA fiber contents by volume, but the improvement extent of impact toughness reduces significantly and the dynamic peak stress decreases. PVA/ECC still has a significant strain rate effect after the high temperature and water-cooled. While when the temperature is greater than or equal to 150 ℃, the strain rate sensitivity of compressive strength reduces.
Axial compressive property of circular steel tubular stub column filled with basalt fiber reinforced recycled concrete
ZHANG Xianggang, ZHOU Gaoqiang, FAN Yuhui, GAO Xiang, LENG Faguang, WANG Fang
2023, 40(1): 369-382. doi: 10.13801/j.cnki.fhclxb.20220317.004
To study the axial compressive performance of basalt fiber reinforced recycled concrete (BFRRC)-filled circular steel tubular stub columns, the replacement ratio of recycled coarse aggregate and the content of basalt fiber were designed as the variable parameters and the axial compression performance tests on 15 BFRRC-filled circular steel tubular stub column specimens were carried out. The failure mode and whole loading process of the specimen were characterized. The load-displacement and load-strain curves of the specimen were obtained. The influence of design parameter on the BFRRC-filled circular steel tubular stub column specimens was analyzed. A feasible full-curve equation of composite-section stress versus strain was established. It is observed that the specimen undergoes buckling damage, but the internal BFRRC is crushed but “broken and not scattered”. On increasing the replacement ratio of recycled coarse aggregate, the energy dissipation capacity and ductility coefficient of the specimen are gradually increased, the maximum increasing extent for energy dissipation capacity and ductility coefficient are 1.84% and 10.36%, respectively, whereas the bearing capacity is gradually decreased, and the maximum increasing extent of bearing capacity is 5.03%. On increasing the basalt fiber content, the energy dissipation capacity and ductility coefficient of the specimen are gradually increased, the maximum increasing extent for energy dissipation capacity and ductility coefficient are 2.97% and 4.93%, respectively, whereas little increase appears about the bearing capacity. The measured load-displacement curve of the specimen with different basalt fiber content is full, and it has a long deformation flow, which presents satisfactory ductility.
Effect of conductive carbon black Super-P on concrete properties
HE Wei, LI Shilei, WANG Yawei, JIAO Zhinan, LI Guifeng
2023, 40(1): 383-395. doi: 10.13801/j.cnki.fhclxb.20211216.002
Nano conductive carbon black Super-P (CBSP) with low cost and high stability was used as additive of cement concrete. By setting different water-cement ratios and different CBSP contents, the effects of CBSP addition on various properties of concrete (slump, mechanical properties, impermeability, electrical conductivity and temperature sensitivity) were studied. The microstructure of concrete was analyzed by SEM. The experimental results show that the slump of concrete decreases with the addition of CBSP. With the increase of CBSP content, the mechanical properties of concrete improve first and then decrease, and the change trend of each age is similar. When the CBSP content is 0.75wt%, the mechanical properties reach the maximum. Meanwhile, the mechanical properties of concrete decrease with the increase of water cement ratio. The impermeability of concrete increases first and then decreases with the increase of CBSP content and decreases when the water-cement ratio is large. When CBSP content is 0.75wt%-2wt%, the resistivity of concrete decreases rapidly. The resistivity of concrete cured by standard curing condition is lower than that cured by indoor drying. The resistivity of concrete with different water cement ratios has little difference. SEM shows that CBSP fills pores and conducts electricity in tunnels. Experiments show that the addition of CBSP can improve the performance of concrete.
Biological and Nano-composite
Construction of microstructured composite coatings based on polyetheramine ED900-tannic acid and cytocompatibility study
HAN Jianmei, XIA Yuxiang, CHENG Fang, HE Wei
2023, 40(1): 396-406. doi: 10.13801/j.cnki.fhclxb.20220128.001
To improve biocompatibility of biomaterials and endow the surface with biological functions, a new type of composite coatings was developed using the natural biomacromolecule tannic acid (TA) and polyetheramine ED900 through a layer-by-layer self-assembly method. The behavior of ED900-TA complexation in water and the physical/chemical properties of the ED900-TA coatings were characterized using nanoparticle sizer, Zeta potential analyzer, UV-vis spectrophotometer, FTIR spectrometer, quartz crystal microbalance (QCM-D), and SEM. The effect of coatings on cell behavior was investigated in vitro. The anti-oxidative property was measured by 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) and total antioxidant capacity assay kit (FRAP) assays. Finally, coating stability was evaluated by agarose insertion and incubation in cell culture medium. The results show the coatings being biocompatible and anti-oxidative. Depending on the surface microstructures, the coatings can be cytophilic or cytophobic. Besides, the coatings can withstand the shear force of insertion and the morphology is maintained up to 21 days in culture medium. This composite coating provides a new option for surface functionalization of biomaterials.
Distribution state of reinforcement phase at the interface between layers in the fused deposition modeling of PLA based biocomposite filaments
ZHOU Zheng, XIE Minghui, WANG Yanqing
2023, 40(1): 407-418. doi: 10.13801/j.cnki.fhclxb.20220414.003
The interlayer interface was unavoidable in 3D parts additive manufactured by fused deposition modeling. Aiming at the enhancement of the interlayer interface, the poly (lactic acid) (PLA) based biocomposite filaments were formerly prepared by the ultrasonic impregnating. In the PLA based biocomposite filament, nano-hydroxyapatite (n-HA) and micron chopped carbon fiber (CF) were firmly bonded and uniformly distributed on the surface of the PLA filament, and they were reserved as reinforcement phases for interlayer interface after being fused. However, after fused deposition modeling, the distribution state of above two reinforcement phases was particularly critical, and it was closely decided by the melting fluid velocity of the nozzle outlet. The influence of three key factors of nozzle diameter, filament feeding speed and micron chopped CF content on the melting fluid velocity of the nozzle outlet was studied, with Ansys being used for fluid numerical calculations, Minitab being applied for orthogonal parameter design and signal-to-noise ratio data analysis, standard tensile samples being 3D printed for tensile performance characterization and distribution state observation of above two reinforcement phases. The results show that the optimization of experimental parameters with Minitab signal-to-noise ratio is more effective than orthogonal experimental parameter design along. Since then, when the melting temperature is 210℃, the nozzle diameter is 0.5 mm, the filament feeding speed is 14 mm·s−1, and the micron chopped CF content is 7wt%, the melting fluid velocity of the nozzle outlet numerically owns the largest variance, which means the most uniform distribution of the above two reinforcement phases in the interlayer interface, and the sample experimentally obtains the strongest tensile properties.
Effect of coupling agent treatment on interfacial bonding strength of carbon fiber/flattened bamboo composite
MA Zhiyuan, GUAN Mingjie
2023, 40(1): 419-427. doi: 10.13801/j.cnki.fhclxb.20220120.004
Carbon fiber/flattened bamboo composite is a new kind of composite material to improve the application of bamboo in engineering products. The bonding interface is the bridge of the transfer force of composite materials, and the bonding property of the bonding interface is the key to the overall mechanical properties of composite materials. The effects of hydroxymethylated resorcinol (HMR) coupling agent on the bonding properties of carbon fiber/flattened bamboo composite were studied. The specimens were divided into four groups according to different forms and treatment methods of flattened bamboo surface. The vertical density distribution, strain distribution, stress transfer and microstructure of the bonding interface of carbon fiber/flattened bamboo composite were measured and analyzed. Results show that the bonding strength of carbon fiber/flattened bamboo composite after treatment with HMR coupling agent is increased by 42.7% compared with that of the untreated group. The bonding interface density of carbon fiber/flattened bamboo composite increases, the thickness of the bondline is wider and the strain distribution and stress transfer more evenly. HMR coupling agent plays a good role in bridging and acts synergistically with carbon fiber to make the stress transfer at the bonding interface more continuous and improves the bonding properties of carbon fiber/flattened bamboo composite.
Microstructure, properties and cytocompatibility evaluation of hydroxyapatite/Ti-13Nb-13Zr composites
WANG Wei, MENG Zengdong, LUO Lilin, ZHANG Yuqin, JIANG Yehua
2023, 40(1): 428-436. doi: 10.13801/j.cnki.fhclxb.20220211.002
In order to improve the bioactivity and cytocompatibility of Ti-13Nb-13Zr biomedical titanium alloy, Ti-13Nb-13Zr alloy and 5HA/Ti-13Nb-13Zr composite with hydroxyapatite (HA) content 5wt% were fabricated by spark plasma sintering (SPS) technique and then annealed. The microstructure, mechanical properties, surface wettability, in vitro mineralization behavior, cell proliferation and apoptosis of the two materials were investigated. The results show that the alloy is mainly composed of β-Ti and α-Ti phases, and the composite is mainly composed of β-Ti, α-Ti, HA phases and a small amount of ceramic reaction phases (Ca3(PO4)2, CaZrO3, CaO). After annealing, the part of α-Ti transforms to β-Ti and the microstructure is more uniform. The addition of HA can refine the grains to a certain extent. The compressive strength, yield strength, yield ratio and elastic modulus of the two materials decrease slightly after annealing. The HA not only strengthens the hydrophilicity and osteoapatite-like formation ability, but also increases cell viability rate and cell apoptosis rate of the composites. Comprehensive analysis, the compressive strength, yield strength and elastic modulus of the 5HA/Ti-13Nb-13Zr are (1744±9) MPa, (1493±12) MPa and (43±1.6) GPa, respectively. Moreover, the 5HA/Ti-13Nb-13Zr composite have excellent bone-like apatite formation ability and the cell viability reaches 99.1%±0.8%. It indicated that the addition of HA significantly improves the bioactivity and cytocompatibility of Ti-13Nb-13Zr alloy.
Preparation and properties of nano-ZnO/bio-based nylon 612 nano-composite antibacterial film
LI Xia, LIU Yuejun, LIU Xiaochao, JIANG Nan, WANG Xionggang, MO Zhixiang, HU Yudi, ZHENG Wei
2023, 40(1): 437-446. doi: 10.13801/j.cnki.fhclxb.20220208.001
Bacterial growth can shorten the shelf life of food and exert a negative effect on human health, therefore it is of great importance to conduct research on anti-bacterial films. Herein, the γ-aminopropyltriethoxysilane coupling agent (KH550) was used to modify nano-zinc oxide, and the modified nano-zinc oxide (m-ZnO) was melt-blended with nylon 612 (PA612) to prepare m-ZnO/PA612 nanocomposite, followed by the fabrication of the antibacterial film through extrusion film casting process. The FTIR was used to characterize the nano-zinc oxide before and after the modification, which proved that KH550 was successfully grafted onto the nano-zinc oxide. Through SEM, DSC, TGA, plate counting method, and other test methods, the dispersibility of nano-zinc oxide and the crystallization performance, thermal performance, and antibacterial properties of composite materials were studied. The results show that the m-ZnO is well dispersed in the PA612 matrix. The m-ZnO can be used as a nucleating agent to increase the crystallinity of PA612. When the content of m-ZnO is 2wt%, the crystallinity is increased by 4.1%. Moreover, the m-ZnO exhibits a reinforcing effect on PA612. When the addition amount of m-ZnO is 2wt%, the tensile strength of the m-ZnO/PA612 nanocomposite film is 15% higher than that of pure PA612. The presence of m-ZnO gives PA612 antibacterial properties. m-ZnO/PA612 nanocomposite film has a good inhibitory effect on Escherichia coli and Staphylococcus aureus. With the increase of m-ZnO content, the antibacterial rate increases, when the mass fraction of m-ZnO is 4wt%, the antibacterial rate against Escherichia coli is 93.25%, and the antibacterial rate against Staphylococcus aureus is 91.03%.
Tensile properties of bamboo fiber/zein composite films based on biochar enhancement
WEI Yuyong, ZHANG Qingfa, LI Kai, FANG Yong, GUO Zihao, YANG Xufeng, SHENG Kuichuan
2023, 40(1): 447-454. doi: 10.13801/j.cnki.fhclxb.20211230.003
In order to improve the tensile properties of zein films, composite films were prepared using ball milled bamboo biochar (0.536 μm) and bamboo fibers (2.157 μm) as enhanced phase and zein as continuous phase by solution pouring method. The basic features and tensile properties of the composite films were studied. The results show that biochar and bamboo fiber do not change the crystal structure of zein, and they increase the disorder, reduce the fragility, and improve the toughness of zein. The addition of biochar improves the hydrophobicity, accelerates the thermal decomposition, and improves the tensile properties of the bamboo fiber/zein composite films. As a comparison, the best tensile properties of the composites films is obtained by adding 0.2 g bamboo fiber and 0.1 g biochar, its tensile strength, tensile modulus, elongation at break are 0.24 MPa, 4.17 MPa, and 327.27%, respectively. The composite films prepared in this study exhibit good toughness showing application potential in packaging film materials.
Metal and Ceramic Matrix Composite
Thermophysical properties of annealed graphite/6061 aluminum alloy composites
ZHANG Yuxiang, GUO Hong, XIE Zhongnan, ZHANG Ximin, HUANG Guojie, XIE Haofeng
2023, 40(1): 455-463. doi: 10.13801/j.cnki.fhclxb.20220217.001
As the heat flux density of electronic devices continues to increase, the hot spots caused by heat accumulation seriously affect the performance and application devices. In this study, annealed graphite (APG)/6061 Al with different graphite layer thickness ratios were prepared using vacuum hot-press method. To enhance the wettability between the annealed graphite and aluminum alloy, annealed graphite was coated with a thin layer of titanium by vacuum micro-evaporation plating, which proved to be effective and efficient. The influence of titanium modification on the microstructure and interface bonding of annealed graphite/aluminum composites was discussed, and the effect of the annealed graphite/aluminum layer thickness ratio on the overall thermal and mechanical properties of the composite was studied. Similarly, the results show that a 400 nm thick interface layer is formed between the annealed graphite and aluminum, and the directionally annealed graphite material modified by titanium is in close contact with aluminum. As the thickness ratio of each phase of Al∶APG∶Al is 1∶3∶1, the composite material has a thermal diffusion coefficient of 901 mm2·s−1 in the in-plane direction and the maximum flexural strength of the composite material is 141 MPa.
Creep rupture time and damage mechanisms of a plain woven SiCf/SiC composite at intermediate temperature
ZHU Siyu, ZHANG Qiaojun, HONG Zhiliang, JING Kaikai, GUAN Haoyang, CHENG Zanlin, LIU Yongsheng, WANG Bo, ZHANG Chengyu
2023, 40(1): 464-471. doi: 10.13801/j.cnki.fhclxb.20220211.001
Silicon carbide fiber reinforced silicon carbide composites (SiCf/SiC) have great potential to be used in the thermal structure of next-generation aero-engines. The creep rupture time tu of SiCf/SiC significantly reduced at intermediate temperatures (~800℃). Therefore, this paper investigated the creep rupture behaviors of a plain weave SiCf/SiC (2D-SiCf/SiC) at 500℃, 800℃ and 1000℃ with stresses of 100 MPa to 160 MPa in air. The morphology, microstructure and compositions of the crept specimens were observed by scanning electron microscopy, transmission electron microscopy and an energy dispersive analysis system. The results show that the tu of 2D-SiCf/SiC is closely related to the applied temperatures and stresses. At the same temperature, tu decreases with the increasing stresses at constant temperatures. When the temperature is 800℃ and the stress is greater than the proportional limit stress (PLS), embrittlement takes place for the 2D-SiCf/SiC, which means the tu and the total creep strain are much shorter than those at 500℃ and 1000℃. The embrittlement mechanisms involve matrix cracking, oxidization of BN and formation of strong fiber/matrix interphase bonding by the filling of SiO2, as well as for the 2D-SiCf/SiC at intermediate temperatures. tu vs. the applied stress follows linear relationship in logarithmic axis, whose transition appears when the applied stress equals to PLS.
Effect of ablation time on ablation mechanism of C/C-SiC composites in hypersonic and oxygen-enriched environment
GAO Yong, WANG Jinjin, ZHA Bailin, WANG Lingling, SHI Yiang, SUN Zhensheng
2023, 40(1): 472-484. doi: 10.13801/j.cnki.fhclxb.20220117.002
In order to study the effect of ablation time on the ablation mechanism of C/C-SiC composites under a hypersonic oxygen-rich environment, the dynamic ablation mechanism of the needled carbon/carbon-silicon carbide composites prepared by “chemical vapor infiltration + precursor immersion pyrolysis” hybrid process was studied by the hypersonic oxygen-enriched ablation test technology in this paper, and the ablation surface morphology of the composites were investigated by scanning electron microscopy. The results show that, the C/C-SiC composites can resist the oxidation working environment of high temperature, high pressure and hypersonic gas jets in a short time under the extremely harsh hypersonic oxygen-enriched ablation environment. The mass ablation rate of C/C-SiC composites after 10 s, 20 s, 30 s, 40 s and 50 s ablation by hypersonic oxygen-enriched ablation are 0.021 g/s, 0.025 g/s, 0.027 g/s, 0.026 g/s and 0.034 g/s, respectively. The dynamic ablation behavior of the C/C-SiC composites under the hypersonic oxygen-enriched environment is synergistic effects of thermo-oxidation ablation and mechanical erosion. In the initial stage, the existence of the SiO2 protective film effectively prevents the diffusion of oxidizing components into the matrix, and only the central area of the material is slightly thermal oxidative ablation. In the middle test, the ablation of the material is mainly manifested in the combined effect of thermo-oxidation ablation and mechanical erosion, and gradually transition from mainly thermal oxidative ablation to mainly mechanical erosion. In the later stage of the ablation test, the further reaction of the matrix makes the ablation mechanism of the material mainly manifested as the large-area flaking of the fiber and matrix.
Preparation and properties of graphene-supported copper reinforced copper matrix bulk composites
FENG Junjun, ZHANG Hui, LI Yapeng, DUAN Jinyu, LIU Yu, PU Zhuolin
2023, 40(1): 485-498. doi: 10.13801/j.cnki.fhclxb.20220307.003
Graphene has a unique two-dimensional structure and properties, which has become one of the ideal reinforcement phase candidates in the preparation of metal matrix composites. Copper has been widely used in electronic products because of its good thermal conductivity, electrical conductivity and chemical stability. But its shortcomings, such as low mechanical strength and low hardness have become a bottleneck problem that need to be solved urgently. At present, the combination of graphene and copper can improve the comprehensive properties of copper matrix materials to a certain extent. However, because graphene is easy to agglomerate and the wettability between graphene and copper is poor, it is difficult to form a good interface between graphene and copper, which leads to the deterioration of the properties of the composites. Therefore, in order to solve the above problem, by chemical reduction method, graphene was modified by reinforcing copper particles on graphene. Finally, the graphene-supported copper composite powder (Cu-rGO) was successfully prepared. Then it was selected the reinforcement phase and mixed with nano-copper powder, and the graphene-supported copper reinforced Cu matrix bulk composite materials (Cu-rGO/Cu) was prepared by the spark plasma sintering (SPS). The effect of the graphene-supported copper composite powder content on the microstructure and properties of copper matrix was studied. The results show that the reduced graphene oxide in the obtained graphene-supported copper composite powder is relatively thin and uniformly distributed with the mass of GO about 50 mg and CuSO4·5H2O about 200 mg. Meanwhile, combined with the TEM structure analysis, it is observed that the contact interface between the copper matrix and the reinforcing phase is close, and the introduction of the reinforcing phase can effectively refine the crystal grains of the bulk composite material. In addition, with the increase of the content of reinforced phase, the hardness first increases and then decreases. Especially, when the content is 2wt%, the hardness increases by 17.6%. However, its conductivity and density show a downward trend, which is due to that the oxygen-containing functional groups in the graphene oxide are not completely reduced during the reduction process, and it may be due to the occurrence of defects and agglomeration of the graphene.
Influence of architecture parameter and mode on compressive properties of an Al2O3p/high manganese steel spherical interpenetrating composite
KOU Baohong, LU Dehong, GONG Wenhao, ZHANG Yi, WANG Yu
2023, 40(1): 499-509. doi: 10.13801/j.cnki.fhclxb.20211230.004
Conventional wear-resistant metal matrix composites generally suffer from low plastic toughness. The spherical interpenetrating architecture design of Al2O3 ceramic particle (Al2O3p) reinforcement high manganese steel composites was carried out, and the effects of the architectured parameters, modes and heat treatment on the compressive properties of the composites were investigated. Al2O3p/high manganese steel spherical interpenetrating composites with three architectured parameters (ball diameter φ of 6 mm, 7 mm, 8 mm) combined with two architectured modes (parallel and staggered), uniformly dispersed composite, and matrix materials were prepared. The results show that the compressive properties of the materials decrease with the increase of the architectured parameters (volume fraction of the composite zone) under the same architectured mode, with the best yield strength, compressive strength, and (under compressive strength) strain for φ6 materials, increasing by 203.8%, 236.1%, and 134.8%, respectively compared with the uniform dispersed composites. The yield strength increases by 107.5% compared with the matrix materials. Under the same architectured parameter, the yield strength, compressive strength and strain of staggered-arrany are increased by 10.9%, 28.5%, and 16.3%, respectively, compared with the parallel-arrany. The yield strength is reduced by 35.2%, the compressive strength is increased by 11.0% and the strain is increased by 163.1% for staggered-arrany composites after water toughness treatment. Cracks tend to sprout and expand at the interface between the matrix and composite zones, but the matrix can hinder the crack expansion. Staggered-arrany increases the minimum spacing of the composites zones and enhances plasticity.
Composite Micro-mechanics
Prediction of ultimate axial strain of FRP-confined concrete based on gene expression programming
DENG Chubing, XUE Xinhua
2023, 40(1): 510-520. doi: 10.13801/j.cnki.fhclxb.20220125.002
Fiber reinforced polymer (FRP) is widely used in enhancing the performance of concrete structures and strengthening damaged components due to its advantages of light weight, high strength, corrosion resistance and convenient construction. The ultimate conditions of FRP-confined concrete are the important factors that must be considered in the selection of FRP types, FRP thickness and the number of covering layer. The prediction results of the existing ultimate stress model can better reflect the real situation, while the prediction accuracy of the existing ultimate axial strain model is low, so the ultimate axial strain was studied. Since there are many factors that affect the ultimate axial strain of FRP-confined concrete, the models proposed by many researchers have large differences in the choice of input parameters. Therefore, the influence of different input forms on the prediction accuracy of ultimate axial strain model was discussed while the ultimate axial strain model was established by gene expression programming. Five statistical indicators such as coefficient of determination and mean absolute error were used to evaluate the prediction results of model, which was compared with the existing prediction models. The research results show that the model corresponding to the input form of the combination of original data and new data has the highest prediction accuracy, so the selection of model input parameters should not only consider the original data or new data. Compared with the models proposed by other researchers, the prediction accuracy of the model proposed in this article is the highest. The coefficient of determination is 0.893, and the mean absolute error and other indicators are all below 0.35.
Mechanical response of inclined Nomex honeycombs under combined shear-compression loads
ZHAO Zhiyong, YUAN Hao, LIU Chuang, LI Yujun, SUN Lishuai, WANG Junbiao
2023, 40(1): 521-529. doi: 10.13801/j.cnki.fhclxb.20220125.001
When forming curved honeycomb sandwich structures, it needs to mill the honeycomb core into a curved shape, resulting in inclined cell walls of honeycombs and reducing its mechanical properties. A detailed finite element model was introduced to analyze the mechanical response and deformation mechanism of inclined honeycombs, and then verified by means of experiments using a specially designed set-up. The simulated results agree well with the experimental ones in terms of the crushing behavior and collapse mechanism. After that, the validated model was used to evaluate the effect of the inclined cell wall angle range from 0° to 40° on the crushing behavior of honeycombs. It is found that the inclined cell wall angle has a significant effect on the crushing response, and the mechanical properties of honeycomb decrease as the inclined cell wall angle increases. When the inclined cell wall angle varies from 0º to 40º, the maximum reduction of initial peak stress and the plateau strength is 47.7% and 29%, respectively. Moreover, the relationship between the dimension of cross-section about inclined cell wall honeycomb cores and the inclined angle was analyzed. The collapse stress of honeycomb under out-of-plane compression and shear loading is deduced by equivalent the inclined cell wall honeycomb as a vertical cell wall honeycomb with the same cross-section dimension, which reveals the influence mechanism of inclined cell wall angle on the properties of honeycombs.
Groove morphology enhancement and parameter design of metal-composite bonding
KANG Zhenhang, LEI Yongpeng, SHI Zhonghua, SONG Quanwei, ZHANG Jifeng
2023, 40(1): 530-541. doi: 10.13801/j.cnki.fhclxb.20220114.001
Metal-composite hybrid joints are widely used in aviation, ship, and automobile. Co-cured metal-composite joints with groove morphology can maintain the integrity of the composite structure and the continuity of fibers. ±45° grooves were designed on the connected metal surface, and the influence of surface morphology on the bonding performance of steel-glass fiber reinforced polymer (GFRP) joints was evaluated. The single-lap joint tensile shear test was designed to verify the shear performance of the bonded joints. In the simulation, the random Weibull distribution was introduced to define the material parameters of the cohesive element, and the progressive failure process of the joint was simulated combined with the vectorized user material (VUMAT) subroutine. The representative volume element (RVE) model of ±45° groove structure was established to analyze the influence of groove width and depth on the adhesive joint. The research shows that the ±45° groove structure can significantly improve the shear strength of steel-GFRP adhesive joints, and the numerical simulation strength and failure mode are consistent with the experiment. The influence of groove depth and width on structural bonding performance is obvious. The research in this paper can provide a reference for the design of metal-composite joints.
Tensile failure mechanism of carbon fiber/epoxy composite L-joints
ZHANG Qi, CAI Deng’an, YU Zhangjie, DAI Zhengzheng, WU Dake, ZHOU Guangming
2023, 40(1): 542-552. doi: 10.13801/j.cnki.fhclxb.20220317.003
Single-L and double-L composite joints were designed with similar weights. A combination of experiment and numerical simulation was used to study the tensile failure mechanism of the two joints. Two kinds of L-joints were quasi-statically loaded to failure on the servo hydraulic testing machine through a self-designed test fixture, and the failure mechanism and strain distribution were analyzed. It’s found that the two L-joints have different failure mechanisms, and the single L-joint exhibits better ductility in the failure stage. When the single L-joints are loaded to the peak load, the damage first occurs near the inner bolt hole in the loading side, and then the damage spreads to the outer bolt hole until failing completely. When the double L-joints are loaded to about 50% of the peak load, the adhesive film between the L-shaped frame and the L-shaped sheet is first damaged, and then when the load continues to increase to the peak load, damage occurs near the bolt holes of the L-shaped frame, extending to the edge of the frame, the load drops significantly. In addition, the strains of the two joints have different trends with the increase of load. Based on a new type of composite material initial failure criterion and stiffness reduction method, a user-defined material subroutine (UMAT) was written. Combined with the cohesive zone model, the progressive damage model of the composite material L-joint was established. Based on ABAQUS software for calculation, the predicted failure load and failure mode of composite single L-joint and double L-joint were obtained. The results show that the damage position and failure mode of the composite L-joint obtained by the finite element analysis are consistent with the test, and the predicted load is slightly different from the test value, which proves the applicability of the finite element model.
Prediction and analysis of cure-induced deformation of composite U-shaped parts with variable thickness
SUN Lishuai, LIU Chuang, LI Yujun, ZHAO Zhiyong, WANG Junbiao
2023, 40(1): 553-566. doi: 10.13801/j.cnki.fhclxb.20220126.001
The micromechanics and the finite element analysis method (FEA) were used to predict the cure-induced deformation (CID) of CCF800H/AC531 carbon fiber/epoxy composite U-shaped parts with variable thickness. The effects of flange and various thickness area parameters on CID were studied by response surface methodology (RSM). The material properties of unidirectional composite were determined by self-consistent method, and the equivalent properties of laminates were calculated by FEA based micromechanical model to avoid the complex layer division and direction definition of the numerical model. The CID of U-shaped parts was predicted by the curing hardening instantaneous linear elastic model (CHILE). A case part was manufactured to verify the accuracy of the FEA. It can be found that the lay-ups and material types have no influence on the law of variable thickness area’s effect on adjacent areas. Then two plans were designed by the Box-Behnken RSM method to analyze the influence of flange parameters and variable thickness area parameters, and two quadratic regression models were fitted, respectively. The investigation reveals that the variable thickness area greatly influences the thinner area, with a maximum reduction of CID of about 15%. The variable thickness area has little effect on the thicker area. Besides, the CID is unaffected by the width of the variable thickness area. The variable thickness area has no effect on the CID of a cross section if it is 150 mm or more away from the cross section.
Meso-model of 2D woven fabric based on free-form deformation technique
GAO Ziyue, CHEN Li, ZHAO Shibo
2023, 40(1): 567-576. doi: 10.13801/j.cnki.fhclxb.20220127.001
In order to avoid the problems of constant cross-section and interpenetration between yarns in the idealized fabric model and generate a realistic three-dimensional meso-model of two-dimensional woven fabric, a geometric deformation method based on free deformation technology was proposed. Firstly, the initial geometric model of the fabric was established through the idealized yarn centerline trajectory and cross-section, and then the free-form deformation technology was applied to deform the yarn. In the deformation process, all yarn cross-sections are free-form to deform under the constraints of spatial position and parameters. The control grid of yarn consists of the control grids after all cross sections being deformed to drive the yarn deformation, and finally a realistic fabric meso-model was generated. The contact between yarns in the deformation process was treated by ray based collision detection technique. This method can be extended and applied to other fabric structures, and can be output to other software for simulation.
Optimum design of ceramic composite armor and residual bending strength after projectile impact
CHEN Zhiyong, XU Yingqiang, LI Miaoling, LI Bin, XIAO Li, SONG Weizhi
2023, 40(1): 577-589. doi: 10.13801/j.cnki.fhclxb.20220214.001
According to the protection requirements and protection mechanism, a C/C-SiC ceramic/Al-based foam metal composite armour was designed. Under the premise that the surface density of the composite armor was ensured to be 44 kg/m2, the residual bending strength after bullet's striking was used as the evaluation standard. The arranged position of the ceramic plate, the thickness of each bulletproof layer and the pore size in the foam metal were the research factors. The orthogonal simulation optimization scheme of three factors and three levels was designed. The numerical simulation of bullet penetration into the ceramic target plates and compression experiment of the composite armors with ballistic damage was carried out by using the finite element software ABAQUS. The residual bending strength of the designed composite armors was predicted and the structure was optimized. The ceramic composite armor samples were prepared according to the numerical simulation results, and the live shooting and bending experiments were carried out to verify their residual bending strength. The results show that the optimum structural form of the ceramic composite armor with the highest residual bending strength based on the MIL-A-46103E protection standard class III 2A is: The thickness of ceramic plate is 12 mm, the ceramic plate is laid out on the bulletproof surface, and the Al-based composite foam has a mixed pore size of 4 mm+10 mm. The order of primary and secondary factors affecting residual bending strength is: Ceramic plate thickness > ceramic plate location > Al-based composite foam pore size.
Failure mechanism of carbon fiber reinforced polymer bonded-bolted hybrid connection
LIU Liping, DUAN Kehao, XU Zhuo, FENG Zhenyu, LIN Yueguo, ZHENG Yimei, SONG Xiaoxiao
2023, 40(1): 590-600. doi: 10.13801/j.cnki.fhclxb.20220215.001
In order to study the failure mechanism of the single-lap two-bolt bonded-bolted hybrid connection of carbon fiber reinforced polymer (CFRP) laminates, the continuous progressive degradation method based on fracture energy fracture criterion was used to simulate the stiffness degradation of CFRP laminates, and the B-K criterion based on energy was used to simulate the damage evolution of the adhesive layer. A three-dimensional finite element model of progressive damage of the bonded-bolted hybrid connection structure was established. The maximum failure load predicted by the finite element model is in good agreement with the experimental results. Lap length La is an important geometric parameter affecting the stiffness and strength of the bonded-bolted hybrid joint. The position of bolt will not significantly affect the stiffness of joint. The larger the bonding area, the greater the strength. Under the action of tensile load, the bolt of the bonded-bolted hybrid joint is inclined to the left due to the influence of the secondary bending effect. The adhesive layer damage in the overlap area starts from the outside of the adhesive layer in the overlap area and expands from the outside to the inside to the vicinity of the bolt hole. When the damage of the adhesive layer extends to the vicinity of the bolt hole, the load of the bolt increases, and the adhesive layer and the bolt bear the load together. At this time, the CFRP laminates begin to damage, and the upper composite plate at the left hole and the lower composite plate at the right hole produce delamination damage and fracture.
Preparation and mechanical properties of glass fiber reinforced 3D fabric reinforced epoxy foam sandwich composites
LI Huaguan, DING Ying, ZHANG Yue, XIANG Junxian, WANG Jie, LI Jianchun
2023, 40(1): 601-612. doi: 10.13801/j.cnki.fhclxb.20220120.001
The preparation and mechanical properties of glass fiber 3D fabric reinforced epoxy foam composites (GF-Fabric/EP composites) were studied in order to further improve the bearing capacity and comprehensive properties of foam sandwich composite materials and realize its application in rail transit and automobile industry. The GF-Fabric/EP composite and its sandwich structure were fabricated. The failure behavior of GF-Fabric/EP composite and its sandwich structure were explored to reveal the reinforcing mechanism of the 3D fabric. The results show that the introduction of 3D fabric can significantly improve the strength, stiffness and failure strain of GF Fabric/EP composites. However, under different load-bearing conditions, each yarn plays a different role and effect. The properties, dimensions and surface/core interface properties of panel and core materials are important factors affecting the mechanical properties and failure characteristics of GF Fabric/EP sandwich composites. Taking the bending properties under three-point loading as an example, for different GF Fabric/EP sandwich composites, it is necessary to adjust the span thickness ratio and specimen size and obtain ideal failure characteristics before effective and reasonable evaluation of their bending properties or interlaminar shear properties.
Tensile failure mechanism of RTM-made asymmetric composite T-joint
WANG Shuai, CHEN Mengxiong, LI Weidong, LUO Chuyang, PAN Lijian
2023, 40(1): 613-624. doi: 10.13801/j.cnki.fhclxb.20220125.003
The tensile tests of structural symmetric and asymmetric composite T-joints prepared by resin transfer moulding (RTM) process were carried out, respectively. The failure process, structure stiffness and failure load of these composite T-joints were compared and analyzed. At the same time, the cohesive zone models (CZM) of composite T-joints were established and the failure process and failure mechanism of these two type T-joints were studied. The interlaminar stress of T-joints with different deflection angles were also compared. The test results show that the failure mode of structural asymmetric T-joint is different from that of symmetric T-joint. The existence of deflection angle causes higher stress at the large angle curved web than that of the small angle curved web, as a result, the initial crack of asymmetric T-joints orientationally occurs at the interface of triangular zone/curved web with large deflection angle. And then the crack directly propagates to the interface of large deflection angle flange/skin with 15.3% higher peak failure load than that of symmetric T-joints. The small bending deformation of the skin of asymmetric T-joint leads to the larger overall stiffness of the structure. The debonding of flange and skin is the prominent reason to the final failure of T-joint. The finite element analysis results show that the simulated peak failure loads of symmetric and asymmetric T-joints are within deviation. The simulated failure mode is in good agreement with the experiment. As the deflection angle increases, the interlaminar stress at the curved web of asymmetric T-joint decreases gradually, which indicates that the initial failure load of asymmetric T-joint may increase correspondingly. The position of initial crack will be shifted to the end of curved web at the same time.
Simulation and experimental study of CFRP micro cutting considering voids defects
LI Shujian, ZHOU Yongchao, CHEN Rong, LI Changping, QIU Xinyi, LI Pengnan
2023, 40(1): 625-636. doi: 10.13801/j.cnki.fhclxb.20220120.008
Carbon fiber-reinforced plastic (CFRP) composites have been widely used in aerospace and other most advanced fields. It is difficult to avoid voids and other defects in the manufacturing process of CFRP, which will have a certain impact on the subsequent machining. Based on the consideration of the voids defects in the process of CFRP forming, a CFRP micro cutting simulation model with void defects was established from the fiber-resin-interface scale by using the finite element simulation method. The micro cutting behavior of CFRP with different fiber orientations under different void content conditions was studied, and the correctness of the simulation model was verified by experiments. The results show that the existence of voids will increase the ‘virtual cutting’ phenomenon of the tool, which will have an impact on the cutting force, material damage, sub-surface damage and material energy in the cutting process of CFRP. The cutting force decreases with the increase of void content, and the tendency of fibers at the edge of voids to produce overall fracture will increase. The voids have little effect on the damage under the machined surface of CFRP with 0°, 45° and 135° fiber orientations. The void content higher than 3vol% has a great effect on the damage under the machined surface when the fiber orientation is 90°. In terms of energy dissipation inside the material, the total dissipated energy in ‘forward cut’ (fiber orientation angle less than 90°) is lower than ‘reverse cut’, furthermore, the total dissipated energy decreases with the increase of void content.