Latest Issue

2023, Volume 40,  Issue 2

Research progress on adsorption properties of biomass materials for micro/nano plastics
Gaojian ZHU, Lidong CHEN, Sheng DUAN, Weibing WU, Hongqi DAI, Huiyang BIAN
2023, 40(2): 637-648. doi: 10.13801/j.cnki.fhclxb.20220621.001
Waste plastics have been accumulated in rivers, lakes and seas. The micro/nano plastics generated by aging and decomposition pollute the water quality seriously and threaten the ecological environment and the safety of drinking water for residents. Traditional treatment methods including physical flocculation and biodegradation, still have problems such as long treatment period and low adsorption efficiency. Natural biomass contains large numbers of active hydroxyl and carboxyl groups. Physical treatment or chemical modification of biomass can be conducted to improve the pore structure and increase the specific surface area, and can be used as a green material for adsorbing micro/nano plastics. This work starts with the conventional treatment methods and the basic characteristics of micro/nano plastics, and briefly summarizes the potential effects and harm of different types of micro/nano plastics on plants, animals and human beings. Then research status of biomass materials (biochar, cellulose, chitin, etc.) in the field of the adsorption of micro/nano plastics is systematically introduced and the adsorption behavior, law and action mechanism of biomass materials on micro/nano plastics are analyzed and summarized. Finally, the future development prospects of the adsorption of micro/nano plastics by biomass materials are prospected.
Research progress in thermoelectric properties of PEDOT∶PSS and its nanocomposites
Chengpeng BAO, Yajie ZHOU, Lan DONG, Zihua WU, Yihuai LI, Huaqing XIE, Yuanyuan WANG
2023, 40(2): 649-664. doi: 10.13801/j.cnki.fhclxb.20220505.001
In recent years, with the aggravation of energy crisis, thermoelectric materials which can directly convert heat energy to electric energy have attracted much attention. Among many types of thermoelectric materials, organic-inorganic hybrid nanocomposites have unique advantages. Compared with inorganic materials, organic materials have the advantages of low cost, light weight, good mechanical flexibility and low thermal conductivity. Once different types of addictions are introduced to form nanocomposites, additional phonon-interface scattering can further reduce the thermal conductivity. Moreover, carrier filtering effect induced by band mismatch between organic and inorganic materials enhances Seebeck coefficient. Therefore, abundance works have proved that organic-inorganic hybrid nanocomposites have the potential to obtain promoted thermoelectric figure of merit (ZT), and have bright application prospects in micro-thermoelectric refrigeration devices, flexible wearable power generation devices, temperature sensors and other fields. This paper focuses on the thermoelectric properties of poly(3, 4-ethylenedioxythiophene)∶poly(styrene sulfonate) (PEDOT∶PSS) thermoelectric materials and its nanocomposites. The physical methods and chemical reagent modification methods to improve the thermoelectric properties of PEDOT∶PSS are reviewed. The research progress of the thermoelectric properties of PEDOT∶PSS based nanocomposites with different types of inorganic fillers is further discussed. The inherent mechanisms of the improvement of thermoelectric properties of PEDOT∶PSS based nanocomposites are also revealed in detail.
Flexible and fiber-shaped batteries—A review
Shuai XU, Jiangdong SUN, Pengfei SUN, Qiaole HU, Wenqi NIE, Zhenzhen XU
2023, 40(2): 665-677. doi: 10.13801/j.cnki.fhclxb.20220527.002
With low dimensionality, flexibility, shape-adaptable, and high integration with textiles, fiber batteries can meet the energy supply needs of circuit elements of flexible electronics. In recent years, research on fiber batteries has not only focused on active materials composited in electrodes, but exploring multi-functional, scalable, and highly integrated systems of fiber batteries. In addition, certain breakthroughs have been made in the large-scale production of fiber-based batteries, including battery assembly, integration, and continuous production. Based on this, this paper discusses the recent research results of fiber batteries in terms of fiber substrate materials and preparation processes, and it also review the latest breakthroughs in the industrial production of fiber batteries. Finally, this paper summarize the problems in the development of fiber batteries and analyze the key difficulties that need to be overcome in the future.
Research progress of application of Ti3C2TX MXenes materials in supercapacitors
Yalin ZHANG, Mengqian WANG, Xinggang CHEN, Yanqing CAI, Ying XU
2023, 40(2): 678-687. doi: 10.13801/j.cnki.fhclxb.20220412.002
In recent years, the demand for energy storage equipment gradually increases, and supercapacitors are favored by researchers because of their excellent performances. Two dimensional transition MXenes are two-dimensional sheet materials similar to graphene, which have unique structure and rich functional groups. Ti3C2TX MXenes have the advantages of good conductivity, high specific area and high specific capacitance, and can be widely used as excellent electrode materials for supercapacitors. However, Ti3C2TX materials have the problems of easy oxidation and self-stacking, and needs to be modified and optimized as electrode materials. This paper mainly introduces the preparation methods of Ti3C2TX materials, such as HF etching, fluoride etching, alkali etching and electrochemical etching, as well as the research methods of performance modification of Ti3C2TX in the application process of supercapacitors, including the construction of Ti3C2TX porous structure, surface modification and preparation of Ti3C2TX composite electrode. The future progress trend of Ti3C2TX supercapacitors is also prospected.
Research progress of flexible electronic devices based on conductive fibers
Wenxiao ZHANG, Xingwei ZUO, Lijun QU, Xueji ZHANG, Jinlei MIAO
2023, 40(2): 688-709. doi: 10.13801/j.cnki.fhclxb.20220511.002
Flexible electronics have excellent flexibility, enabling seamless integration with clothing, and have great potential in various practical wearable applications. One-dimensional fibrous electronic devices have become a research hotspot in the field of smart wearables due to their excellent flexibility, weavability and comfort. First, the research progress of one-dimensional stretchable electrodes for fiber-like flexible electronic devices is reviewed, and then introduced the high-performance one-dimensional fibrous flexible electronics representative during the preparation of conductive material, manufacturing technology, as well as the further application of the one-dimensional flexible fiber become various main preparation methods for all kinds of electronic devices. Finally, we think critically about the opportunities and challenges of one-dimensional wikis smart wearable electronics.
Research progress on preparation and modification technology of conductive polymer corrosive protection coatings
Yijie JIN, Zhihao CHEN, Wenzhong YANG, Shengpeng ZHAN, Dan JIA, Wulin ZHANG, Lixin MA, Haitao DUAN
2023, 40(2): 710-725. doi: 10.13801/j.cnki.fhclxb.20220512.006
The marine engineering equipment manufacturing industry in China is in the critical stage of survival and development. The anti-corrosion coating is one of the most effective ways to reduce the corrosion rate of the substrate and improve its service life. Conductive polymers (CPs) coatings have been widely used in the field of metal corrosion protection due to its advantages of environmental protection, simple preparation and unique conductive and anticorrosive mechanism. This work summarizes the anticorrosion mechanism of CPs coatings, introduces the current situation of preparing conductive polymer coating by two methods of chemical oxidation and electrochemical synthesis, and focuses on the improvement effect of doping modification, copolymerization modification and layered design of CPs coatings on the corrosion resistance of the coating. Finally, the possible research hotspots and development trends of CPs coatings in the field of corrosion protection are proposed.
Research progress of high-efficiency double-junction perovskite tandem solar cells
Meirong ZHANG, Zengwei ZHU, Xiaoqi YU, Tongxu YU, Di LU, Shunfeng LI, Dayong ZHOU, Hui YANG
2023, 40(2): 726-740. doi: 10.13801/j.cnki.fhclxb.20220923.002
Perovskite tandem solar cells have developed rapidly and become one of the hotspots in the field of solar photovoltaic research. With the optimization of the structure and preparation process, the power conversion efficiency (PCE) of tandem device has been improved greatly. The perovskite/silicon tandem solar cell has been greatly improved and the efficiency has reached 31.3% for monolithic tandems. We sorts out the development of the tandem solar cell with wide bandgap perovskite as the top sub-cell and crystalline silicon cells and other novel medium-narrow bandgap cells (perovskite cells, organic cells, copper indium gallium selenide (CIGS) cells) as the bottom sub-cells in recent years and systematically summarized the key point and challenge in materials, structures, and optoelectronic properties of top cell, intermediate interconnection layers and bottom cells in this review with the hope that provide some ideas for further improving the PCE of tandem cells. The optical and electrical optimization requirements for low-cost and high-efficiency tandem solar cells in the future are also highlighted.
Resin Polymer Composite
Properties of bismaleimide resin modified by addition-curing phenolic and their composites
Weifang JIANG, Linxiang WANG, Qing ZHENG, Qiaolong YUAN, Farong HUANG
2023, 40(2): 741-752. doi: 10.13801/j.cnki.fhclxb.20220321.004
Bismaleimide (BMI) resin has been widely used in aerospace, electronics and other industrial fields because of its excellent properties. In order to meet the needs of structural components for high-speed aircraft, the additional phenolic modifier is introduced to improve the thermo-mechanical properties of BMI resin. The propargyl etherified novolac (PN) and allyl etherified phenolic (AN) as an addition modifier were synthesized by Williamson etherification. The PN and AN were used to modify N, N'-(4, 4'-diphenylmethylane) bismaleimide (BDM)/2, 2'-diallyl bisphenol A (DABPA) resin system (BD) in melting mixing to obtain the ternary blended resins of BDPN and BDAN. The processability and cure reactions of the BDPN and BDAN were studied. The thermal property and mechanical property of the cured BD, BDPN and BDAN were further investigated. The results show that the ternary blended resins exhibit good solubility and meltability, and have an above 50℃ of process window. There is only a single exothermal peak in DSC curves of BDPN and BDAN. The peak temperatures of BDPN and BDAN are lower than that of BD. The Fourier transform infrared (FTIR) was used to monitor the curing reactions of BD, BDPN and BDAN resins. The reactions of Ene, Diels-Alder, Claisen rearrangement and addition of alkyne and maleimido group were detected during curing. The cured PN resin has good thermo-oxidative stability. The residual yield at 800℃ (Yr800℃) of cured BD in air increases from 3.7% to 23.1% after the BD resin was modified with PN resin. The temperature of 5wt% mass loss (Td5) of the cured BDPN in air is higher than 400℃. The limited oxygen index (LOI) of the cured BD, BDPN and BDAN resins are 30.2%, 32.5% and 31.0%, respectively. The cured resins are nonflammable. The impact strength and flexural modulus of the cured BD resin increase with addition of PN and AN resins. The impact strength and flexural modulus of the cured AN modified BD resin increase by 19% and 30% respec-tively. However, the flexural strength of the BDPN and BDAN resins decrease since the crosslinked density of the cured modified resins decline. The water absorption in boiling water of the cured BDPN and BDAN resins are lower than that of the cured BD resin, and decrease by 8.6% and 14% after 40 h. The flexural strength, flexural modulus and interlaminar shear strength (ILSS) of the T300 carbon fiber cloth (T300CF) reinforced BDAN composite (T300CF/BDAN) at room temperature are higher than that of the T300CF reinforced BD composite. The flexural strength of the T300CF/BDPN at 200℃ retains a 98.6% retention, reaches to 575 MPa. The propargyl etherified novolac can used to improve the heat properties of bismaleimide which is a new approach for modification of bismaleimides, and promising to be utilized in preparation of the structural components of composite with heat-resistance at 200℃.
Investigation of the bonding performance of a protein dispersed carbon nanotube/epoxy adhesive
Junjie ZHAO, Wenwu TAO, Lijian ZENG, Yichao LI, Renfu LI, Kun WANG
2023, 40(2): 753-760. doi: 10.13801/j.cnki.fhclxb.20220412.003
Carbon nanotube (CNT)/epoxy resin can be widely used to bond advanced structural parts in the aerospace field due to its excellent mechanical and bonding properties. However, how to effectively reduce the agglomeration of carbon nanotubes and ensure low cost and environmental protection of the preparation process is the key to the practical application of the nano-binder. Therefore, this paper proposes a protein dispersed carbon nanotube reinforced epoxy resin adhesive and investigates its bonding performance. The results show that the soy protein isolate (SPI) after a certain acid or alkali denaturation treatment can effectively reduce the agglomeration of carbon nanotubes and significantly improve the bonding performance of epoxy resin. When the CNT loading is 0.1wt%, the bonding property of acid and alkali treated SPI-CNT/epoxy is increased by 26.6% and 26.7%. While the CNT loading increases to 0.3wt%, the bonding property enhancement of the two treated methods comes to 10.2% and 18.3%, the alkali method is 79% higher than the acid one.
Impact resistance of continuous glass fiber and glass bead co-reinforced Nylon 6 composites
Hongfeng YIN, Feibiao XUE, Ying WEI, Shun YANG, Yun TANG, Hudie YUAN, Xiaohu REN
2023, 40(2): 761-770. doi: 10.13801/j.cnki.fhclxb.20220330.001
Low-velocity impact is a common damage mode for polymer matrix composites during transportation and service, often results in structural damage, performance degradation, and loss of load-bearing capacity, which affects the use of the composites. To address the problem of poor delamination resistance of 2D fiber-reinforced polymer matrix composites under impact loading, binary and ternary Nylon 6 (PA6)-based composites were prepared by melt extrusion combined with hot pressing, and the pendulum impact performance and drop hammer low-velocity impact response of continuous glass fiber (GF), glass beads (GB) and both co-reinforced PA6-based composites were comparatively investigated. The results show that: (1) GF and GB can significantly improve the impact resistance of PA6, and the enhancement effect of GF is significantly higher than that of GB; (2) Impact strength of GB-reinforced PA6-based composites (GB/PA6) showed a trend of increasing and then decreasing with increasing GB incorporation, with the maximum impact strength at 25wt% incorporation; the energy dissipation mechanism of 25wt%GB/PA6 under impact loading was found to be a new mechanism of slip energy dissipation of GB in PA6 matrix, in addition to interfacial debonding and pinning effects; (3) The fibers in GF and GB co-reinforced PA6 composites (GB-GF/PA6) play a major reinforcing role, and both pendulum impact tests and drop impact tests demonstrate a synergistic reinforcing effect; (4) The synergistic reinforcing effect of GF and GB co-reinforcement is due to the increased resistance to type II crack expansion of the co-reinforced composites under impact loading, resulting in the reinforcement of the composite against delamination. Thus, demonstrating that the introduction of an appropriate amount of spherical GB into the matrix is an economical and effective way to improve the resistance of 2D fiber-reinforced polymer matrix composites to low-velocity impact.
Compression after impact properties of carbon-fiber/aluminum-honeycomb sandwich panels with short-Kevlar-fiber toughening
Shanshan SHI, Chaoyu LV, Hangyu LV, Gong CHENG, Zhi SUN
2023, 40(2): 771-781. doi: 10.13801/j.cnki.fhclxb.20220305.001
Delamination between face sheets and core is one of the most common damage mode of carbon-fiber sandwich panels under impact loading, which seriously affects structural safety. Firstly, short-Kevlar-fibers were used for toughening the interface of carbon-fiber/aluminum-honeycomb sandwich panel. Secondly, low velocity impact and compression after impact tests were conducted for plain and toughened specimens. The residual compression strength, energy absorption and failure mode were compared. Finally, the strains of plain and toughened specimens during compression after impact test were obtained by digital image correlation (DIC). The results show that short-Kevlar-fiber toughening is capable to effectively increase the impact damage resistance of carbon-fiber/aluminum-honeycomb sandwich panel, and the damage threshold load of toughened specimens is signifi-cantly higher than that of plain specimens. Compared with the plain specimens, the residual compression strength values after impact of toughened specimens are increased by 2.68%, 9.24%, 4.65% and 11.13%, respectively, under four different impact energies. Meanwhile the energy absorption values of toughened specimens are increased by 69.09%, 52.88%, 55.03% and 101.70%, respectively. Furthermore, DIC observations were used to investigate the toughening effects of short-Kevlar-fibers and the strengthening mechanism.
Simulation and optimization of infusion process for perforated foam sandwich composite
Herong SHI, Jihui WANG, Aiqing NI, Yuwei FENG, Xiang LI
2023, 40(2): 782-793. doi: 10.13801/j.cnki.fhclxb.20220323.001
The numerical simulation of the vacuum assisted resin infusion (VARI) process of perforated sandwich composite was verified experimentally, and process optimization was presented thereafter. Firstly, the permeabilities of the fabric and holes of perforated core were obtained experimentally and numerically, respectively. Then, 3D simulation was carried out for the infusion process of the perforated sandwich composite structure and verified by real-scale infusion experiments. Finally, based on the simulation, the process was optimized by investigating the effects of injection position and type on the filling time and product porosity, and later a methodology was proposed to predict the filling time needed. The results show that the numerical simulation is in good agreement with the experiment. The flow patterns during the filling and the porosities of the perforated sandwich structures are in good match with experimental results. The filling time prediction method can be used for practical production instruction. The selection of proper parameters, such as injection position and type, can minimize molding time and product porosity.
Comparison of pyrolysis and combustion characteristics of carbon fiber, glass fiber/epoxy resin
Junhao MA, Xuhong JIA, Jing TANG, Xiaoyu ZHANG, Shangpei DAI, Xiaoguang YANG
2023, 40(2): 794-803. doi: 10.13801/j.cnki.fhclxb.20220325.002
Civilian aircraft interior wall panel materials are mainly fibre/resin composites, which have a certain fire hazard, so the study of their thermal stability and combustion characteristics is of great significance for aircraft fire protection. A thermogravimetric analyzer was used to study the influence of different heating rates on the pyrolysis of two typical aircraft siding materials: Carbon fiber/epoxy resin and glass fiber/epoxy resin, and the apparent activation energy and pre-digital factor of the decomposition stage were obtained using the Kissinger method. The cone calorimeter was used to study the combustion characteristics of two prepregs in different fire environments, and four evaluation indicators of fire growth index (\begin{document}$ {\delta _{{\rm{FGI}}}} $\end{document}), fire potential index (\begin{document}$ {\delta _{{\rm{FPI}}}} $\end{document}), thermal heat release index (\begin{document}$ {\delta _{{\rm{THRI}}}} $\end{document}) and thermal smoke produce index (\begin{document}$ {\delta _{{\rm{TSPI}}}} $\end{document}) were selected to evaluate the fire hazard; and then the two types of fibers were analyzed. Furthermore, the influence of the two kinds of fibers in the pyrolysis and combustion process of the resin composite was analyzed. The results show that in air atmosphere, the heating rate has a greater influence on the pyrolysis of the two prepregs. The carbon fiber decomposes above 556℃, and the glass fiber does not decompose. During pyrolysis, the activation energy of the first two stages of the glass fiber prepreg is significantly higher than that of the carbon fiber prepreg, indicating that the glass fibre prepreg has a higher thermal stability. The heat release rate, smoke production rate, total heat production, and total smoke production of carbon fiber prepregs are greater than those of glass fiber prepregs. As the heat radiation intensity increases, the differences between these parameters of the two prepregs are all keep getting bigger, the \begin{document}$ {\delta _{{\rm{FGI}}}} $\end{document}, \begin{document}$ {\delta _{{\rm{THRI}}}} $\end{document} and \begin{document}$ {\delta _{{\rm{TSPI}}}} $\end{document} of carbon fiber prepreg are larger than glass fiber prepreg, while the \begin{document}$ {\delta _{{\rm{FPI}}}} $\end{document} value is the opposite. The analysis finds that both fibres inhibite the pyrolysis of the composite, but the glass fibre inhibites it more significantly and the carbon fibre/epoxy composite have a greater fire hazard.
Prediction of the effective elastic properties for plain woven fabric composite based on the structural parameters
Jun ZHU, Lin GUI, Guo LI, Menghai YU, Jihui WANG
2023, 40(2): 804-813. doi: 10.13801/j.cnki.fhclxb.20220424.004
The warp and fill fiber strands interlacing in two mutually orthogonal directions to one another results in the fiber curvature, namely the waviness, which is the inherent characteristic of plain woven fabric composite. First, a mathematical description was developed to accurately represent the 3D architecture morphology of the unit cell for plain woven fabric composite. Next, an analytical multi-parameter model of plain woven fabric composite was established based on the classical lamination theory and iso-stress assumption. Meanwhile, the bending-extension coupling effect due to asymmetry along the thickness-direction as well as the architecture morphology of the unit cell was embedded in this model. The validation of several typical cases shows that the predicted effective elastic properties of plain woven fabric composite agree well with the numerical values of the finite element model, the results of the analytical model and the experimental data cited in the related literatures. Also, the predictions of the analytical multi-parameter model, especially the Z-direction ones, are more approaching to the experimental data than counterparts of other analytical models aforementioned. Furthermore, the influence of the structural parameters such as the waviness ratio of the fiber strand containing both the undulation direction and the cross section, the thickness of the preform consisting of the warp and fill fiber strands, the length of the curved section of the fiber strand and the spacing between the adjacent fiber strands on the elastic properties of plain woven fabric composite is elaborated. The present approach of the analytical multi-parameter model provides a reference for evaluating the mechanical properties of textile composite.
Functional Composite
Water-soluble zirconium hybrid silicone resin sizing for improvement heat resistance of basalt fibre
Yan CHENG, Zhaotian WANG, Hongjie LUO, Linli WU, Xiping CHEN, Hao JIANG
2023, 40(2): 814-824. doi: 10.13801/j.cnki.fhclxb.20220426.001
The working temperature of the existing high-temperature basalt fibre filter bag is 280℃, they are difficult to work for a long time when the temperature is above 300℃. In order to improve the heat resistance of basalt fibres, in this paper, a kind of water-soluble zirconium hybrid silicone resin sizing agent was synthesized and used for basalt fibre surface modification. Microstructure and properties of zirconium hybrid silicone resin and modified fibers were characterized by FTIR, TG-DSC, SEM, AFM, DCA and tensile test. The results show the decompose temperature of zirconium hybrid silicone resin is 323-360℃. The surfaces of the sized fibres are coated by dense and uniform silicone resin films. These films increase the surface roughness and surface areas of the fibre surfaces, improve the surface energies, change the surface morphologies, repair the surface micro defects. Themechanical tests show that after heat treatment of 2 h at 300℃, the breaking force of optimum sample is 376.0 N, and the breaking elongation is 2.647%, which are better than the related performance of uncoated fibre (287.8 N, 1.932%). Therefore, the zirconium hybrid silicone sizing agent could significantly improve the heat resistance of basalt fibre.
Preparation and properties of hexagonal boron nitride/semi-aromatic polyamide 12T composites with high-temperature resistance and high thermal conductivity prepared by mixed solvent dispersion method
Xiaojie CHEN, Ge MA, Huidi MENG, Zhe CUI, Peng FU, Wei ZHAO, Xinchang PANG, Qingxiang ZHAO, Minying LIU, Xiaomeng ZHANG
2023, 40(2): 825-835. doi: 10.13801/j.cnki.fhclxb.20220321.003
Fabrication of the polymer-based composites with excellent high temperature resistance and thermal conductivity is very important for the packaging protection, efficient heat dissipation and processing of electronic components. In this work, high temperature resistant and thermally conductive hexagonal boron nitride (BN)/semi-aromatic polyamide 12T (PA12T) composites with uniform dispersion and orientation filler structure were prepared by mixed solvent dispersion (MSD) method, and the microstructure, thermal conductivity, high-temperature resistance, dielectric and mechanical properties of the composites were systematically characterized. The results show that the BN powder and PA12T powder can be suspended uniformly in the mixed solvent. Next, combining the vacuum-assisted self-assembly technique and vacuum hot compression method, the composites with uniformly dispersed and oriented BN structure are fabricated successfully. When the content of BN is 40wt% in BN/PA12T composite, the in-plane thermal conductivity of the composite prepared by the MSD method is 2.73 W/(m·K), which is 1.72 times that of the composite (1.59 W/(m·K)) prepared by the mechanical mixing (MM) method. Furthermore, the composite prepared by the MSD method also possesses excellent mechanical properties, low dielectric permittivity of 3.6 and dielectric loss of 0.016, outstanding high-temperature resistance with the initial decomposition temperature of 446℃ and Vicat softening temperature of more than 250℃. Therefore, the BN/PA12T composite prepared by the MSD method will have a wide range of applications in the fields of electronic packaging and thermal management.
Preparation and antibacterial properties of porous polyacrylonitrile composite fiber membrane loaded with silver/copper nanoparticles
Peng XU, Yang WANG, Shasha WANG, Wei DAI, Nannan CHEN, Qun LI
2023, 40(2): 836-843. doi: 10.13801/j.cnki.fhclxb.20220419.005
Metal nanoparticles show great application on prospect in catalysis, bacteriostasis, water pollution treatment and biomedicine, because of their unique physical and chemical properties. Metal nanoparticles tend to agglomerate in the processes of preparation and use. Therefore, improving the stability of nanoparticles is of great significance to improve their application performance. In this study, porous polyacrylonitrile nanofibers (PPAN NFs) were prepared by electrostatic spinning using polyacrylonitrile (PAN) as substrate and polyvinylpyrrolidone (PVP) as the pore-making agent. On this basis, Ag-PPAN NFs and Cu-PPAN NFs were prepared by in-situ loading of silver and copper nanoparticles on the surface of PPAN NFs by impregnation deposition. The morphologies and structures of the prepared nanofibers were characterized by FESEM, EDS and XRD, and the antibacterial properties of Ag-PPAN NFs and Cu-PPAN NFs against E. coli, S. aureus and C. albicans were studied by bacteriostatic zone method and FESEM observation. The results show that PPAN NFs provide a rich mesoporous structure for loading of Ag NPs and Cu NPs and inhibited the aggregation of nanoparticles. The prepared Ag-PPAN NFs and Cu-PPAN NFs show good antibacterial activities against E. coli, S. aureus and C. albicans, and which could be used as a new kind of antibacterial fiber material.
Transition metal and phosphorus co-doped porous carbon as electrocatalyst for oxygen reduction
Zeyuan WAN, Guilin LI, Jiao WU
2023, 40(2): 844-851. doi: 10.13801/j.cnki.fhclxb.20220228.002
Carbon-based materials, as non-noble catalysts, have attracted extensive attention in the field of cathode catalysts for fuel cells due to their high conductivity, long-term stability, low-cost and environmental friendliness. Especially, the oxygen reduction reaction (ORR) activity of carbon materials can be significantly improved after co-doping with transition metal and heteroatoms. In this work, transition metal (Co, Fe, Ni, Mn) and phosphorus (P) co-doped porous carbon (TM-P-C) was prepared via self-assembly method combined with a carbonization process, in which polyether (F127) was introduced as soft template, phenol and formaldehyde as carbon precursor, tetraphenylphosphine bromide as phosphorus source, and nitrate as transition metal source. The electrocatalytic activity of TM-P-C for ORR in alkaline electrolyte was studied by using the rotating ring-disk electrode (RRDE) technique. The results reveal that TM-P-C exhibits high electrocatalytic performance for ORR in 0.1 mol/L KOH, and the activity follows P-Co-C>P-Ni-C>P-Fe-C>P-Mn-C. Moreover, the ORR performance of P-Co-C is compared to that of commercial 20wt%Pt/C catalyst. The diffusion limiting current density of P-Co-C reaches that of 20wt%Pt/C and a negative shift of about 66 mV exists in the half-wave potential of P-Co-C as compared to 20wt%Pt/C, indicating the four-electron pathway during the ORR. The enhancement in the activity for ORR is mainly attributed to the synergistic effect of P and transition metal doping in carbon of TM-P-C. Moreover, TM-P-C shows excellent long-term stability and methanol toxicity resistance, superior to that of commercial 20wt%Pt/C.
Isocyanate modified fumed silica and its effects on the mechanical properties of casting polyurethane elastomer
Xin ZHOU, Yuhua YI
2023, 40(2): 852-859. doi: 10.13801/j.cnki.fhclxb.20220303.002
In order to improve the molding fluidity of fumed silica (FS)/cast polyurethane (PU) system, in the process of preparing prepolymer, the fumed silica (FS) was modified by 2, 4-toluene diisocyanate (TDI) to obtain TDI modified silica (NCO@FS), and TDI modified silica/reinforced pouring polyurethane (NCO@FS/PU) elastomer composite material was prepared by in-situ polymerization. NCO@FS and FS were characterized by fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle testing. The results show that the active hydroxyl groups on the surface of FS react with the —NCO groups of TDI to form urethane groups aminoester group (—NHCOO), which improves the interfacial compatibility and interfacial bonding between silica and casting polyurethane. When the mass fraction of NCO@FS in the composite material is 1.5wt%, the tensile and tearing strengths of the NCO@FS/PU composite material are 57 MPa and 110.5 kN/m, respectively, which are 31.6% and 23.6% higher than that of pure casting PU. The glass transition temperature dropped from 3.4°C to –11.2°C, and the loss factor tanδ dropped from 0.59 to 0.46. TDI modified fumed silica is suitable for preparing silica-reinforced cast polyurethane composites.
Microstructure and thermoelectric properties of MWCNT/PEDOT composites
Chongyang LI, Xiaoyong SONG, Lili CHEN, Ying TAO, Zhiquan CHEN, Bin ZHAO
2023, 40(2): 860-871. doi: 10.13801/j.cnki.fhclxb.20220307.002
Thermoelectric conversion technology can convert a large amount of waste heat energy into electric energy for reuse. It is a green energy conversion technology, which can effectively improve energy utilization, and alleviate the energy crisis and environmental pollution caused by the over-exploitation and utilization of coal, oil and other major fossil energy. Therefore, it has been widely concerned by researchers and has become a research hotspot recently. Base on this, one of the more excellent electronic conductive polymers, poly(3, 4-ethylenedioxythiophene) (PEDOT), was used as the research subject, and multiwall carbon nanotubes (MWCNT)/PEDOT composites were synthesized by chemical in situ oxidation synthesis method. X-ray diffraction, raman spectroscopy, transmission electron microscope and positron annihilation lifetime spectroscopy were used to study the microstructure of the composites, the results of which indicate that when the MWCNT content is higher than 24.9wt%, the MWCNTs of MWCNT/PEDOT composites aggregate seriously and are badly dispersed. Thermal and electrical measurements of MWCNT/PEDOT composites show that their electrical conductivity increases sustainably with the MWCNT content increasing. For the pure PEDOT sample, the electrical conductivity is only 7.5 S·m−1, and the electrical conductivity of MWCNT/PEDOT sample is up to 566.59 S·m−1 at MWCNT content of 30.1wt%, the increase is nearly 76 times. Meanwhile, the power factor of the composites increases rapidly from 14.5×10−4 to 814.3×10−4 μW·(m·K2)−1 with the increase of 56, which is mainly due to the high conductivity of MWCNT and the π-π interaction between PEDOT molecular chain and MWCNT. With the increase of MWCNT content, the decrease of the first lifetime τ1 of positron annihilation in materials of PAL test confirms that the interface between MWCNT and PEDOT became smaller and the interfacial interaction between the MWCNT and PEDOT was weakened. As a result, the thermal conductivity of the composite exhibits a bit increase with the addition of MWCNT, but it was far lower than the increase of power factor. Eventually, the thermoelectric figure of merit (ZT, an index or measure of the thermoelectric properties of a thermoelectric material) value of the MWCNT/PEDOT composites increases from 0.015×10−4 to 0.45×10−4, that's a nearly 30-fold increase. In summary, the doped MWCNT of higher conductivity can greatly enhance the thermoelectric properties of electronic conductive polymers of PEDOT.
Construction and property regulation of nano-SiO2@hyperbranched PDMS composite superhydrophobic coating
Jing LIU, Xiping LEI, Ting YU, Haonan CHEN, Kai FAN
2023, 40(2): 872-883. doi: 10.13801/j.cnki.fhclxb.20220331.002
In practical application, affected by chemical corrosion, scratch and wear and other external environment, superhydrophobic coating is easy to aging, cracking and even falling off, resulting in coating failure. Therefore, to solve this problem, a self-healing superhydrophobic surface with weather resistance was designed: Hyperbranched polydimethylsiloxane (PDMS) was used as a flexible substrate and low surface energy material, and nano-silica was introduced to construct the surface rough structure to prepare the superhydrophobic coating. When SiO2 particle size is 50 nm and solid content is 30wt%, the superhydrophobic coating with contact angle of 154.87° is obtained. The coating shows good mechanical stability after 5 times of tape peeling test. After 10 temperature difference cycling tests and 24 h UV irradiation, the surface contact angle is still greater than 150°, indicating that the coating has good weather resistance. The scratches can be partially healed by heat treatment at 80℃ for 2 h, indicating that the coating has certain self-healing function. At the same time, Tafel and Nyquist test results indicates that superhydrophobic treatment can significantly improve the corrosion resistance of the substrate, and the coating has obvious self-cleaning effect as well. In conclusion, the nano-SiO2@hyperbranched PDMS composite superhydrophobic coating prepared in this work has self-healing function, which provides a new research strategy for the development of self-healing superhydrophobic coating.
Preparation and its Cr(VI) adsorption properties of biomimetic FeS composites
2023, 40(2): 884-892. doi: 10.13801/j.cnki.fhclxb.20220402.001
Nano FeS has excellent adsorption performance for Cr(VI) because of large specific surface area and strong reducibility, but it is unstable and prone to agglomeration. In order to overcome these disadvantages, the biomimetic FeS composites (bioFeS) were prepared by co-precipitation-roasting method using rape pollen as a biological template. The surface morphology and structure of bioFeS composites were characterized by SEM, XRD and XPS. The effects of adsorbent dosage, reaction time, reaction temperature, initial Cr(VI) concentration and pH on adsorption capacity of Cr(VI) on bioFeS composites were studied to investigate the reaction mechanism using Cr(VI) as the target pollutant. The results show that rape pollen biotemplate successfully disperse FeS with a large specific surface area. The adsorption capacity of Cr(VI) on bioFeS composites can reach 88.95 mg·g−1 at a reaction time of 120 min, pH of 1, adsorbent dosing of 0.2 g·L−1 and a reaction temperature of 25℃. The adsorption process conforms to quasi-secondary kinetics and the Langmuir isothermal adsorption model. The coexisting ions NO3 and SO42− will inhibit the adsorption capacity of Cr(VI). Combining with adsorption kinetics, thermodynamics and XPS surface element analysis, the mechanism of chromium removal by bioFeS composites mainly involves adsorption and chemical reduction. The method of removal of Cr(VI) in wastewater by bioFeS composites has a promising application.
Room temperature preparation of NiFe-phytic acid composite and its electrocatalytic performance for overall water splitting
Yingyu CHEN, Yijun LIU, Chenxin CHEN, Qingxiang WANG, Feng GAO, Wei SUN
2023, 40(2): 893-903. doi: 10.13801/j.cnki.fhclxb.20220314.002
The preparation of bifunctional catalysts with high stability and high activity for hydrogen production from water is one of the important step in the large-scale commercial application of hydrogen energy. Herein, the flake amorphous phytic acid-nickel iron bimetallic composite (NiFe-PA) has been prepared on foamed nickel (NF) by two-step room temperature impregnation using phytic acid (PA), ferric chloride hexahydrate (FeCl3·6H2O) and nickel chloride hexahydrate (NiCl2·6H2O) as the starting materials. The electrocatalytic performance of NiFe-PA modified NF electrode (NiFe-PA/NF) for water electrolysis in alkaline condition (1.0 mol/L KOH) was investigated by linear sweep voltammetry (LSV). The results show that NiFe-PA/NF, as a bifunctional catalyst, has excellent oxygen and hydrogen evolution properties due to the synergistic effect between Ni and Fe. The overpotentials are only 220 mV at 50 mA·cm−2 for oxygen evolution reaction (OER) and 135 mV at 10 mA·cm−2 hydrogen evolution reaction (HER). The NiFe-PA/NFs were then assembled into a two-electrode system for overall water splitting, and the cell voltage required to reach the current density of 10 mA·cm−2 was only 1.61 V, which is lower than the precious metal catalyst system of RuO2/NF||Pt-C/NF (1.64 V). It can also satisfy the hydrogen production driven by solar panels (2 V) under solar illumination conditions. Furthermore, owing to the high stability and corrosion resistance of the PA-metal complex, the catalytic stability of NiFe-PA/NF can be maintained at least for 175 h and 75 h, respectively, for the OER and HER at 100 mA·cm−2, indicating the high catalytic stability of NiFe-PA/NF at high current densities.
Preparation and visible light catalytic performance of g-C3N4/POPs heterojunction
Jiayun GUO, Yangjie FU, Kejie ZHANG, Yun JI, Juan YANG, Qi WANG
2023, 40(2): 904-910. doi: 10.13801/j.cnki.fhclxb.20220325.001
As a promising environmental remediation technology, the development of efficient and stable photocatalysts with visible light response is one of the important studies in photocatalysis technology. In this work, g-C3N4/porous organic polymers (POPs) composite photocatalysts were prepared via atmospheric solvothermal method. Different ratios of g-C3N4 were in-situ loaded on conjugated porous organic polymers TAPB-DMTP POP synthesized with 1, 3, 5-tris(4-aminophenyl) benzene (TAPB) and 2, 5-dimethoxybenzene-1, 4-diformaldehyde (DMTP) as monomers. The chemical structure and optical properties of g-C3N4/POPs materials were characterized by XRD, FTIR, BET, TGA, UV-Vis DRS, current-time (i-t) and EIS methods. Cr(VI) was selected as the model pollutant, the photocatalytic reduction activities of g-C3N4/POPs photocatalysts with different g-C3N4 loading ratios were explored under visible light conditions, and the effects of pH value, catalyst dosage and substrate concentration were further investigated. The results shows that g-C3N4/POP-2 exhibits the best photocatalytic reduction performance at pH=2 with the reduction efficiency of 99.1% after 30 min of visible illumination. The reduction efficiency of Cr(VI) is significantly improved over g-C3N4/POP-2 compared with pure g-C3N4 and TAPB-DMTP POP, and the fitted first-order kinetics rate are 22.0 times and 2.2 times that of g-C3N4 and TAPB-DMTP POP, respectively. This composite also exhibits excellent photocatalytic stability as the Cr(VI) reduction rate reaches more than 90% after five cycles.
Graphene-enhanced electromagnetic wave absorbing properties of FeSiAl-MoS2/PLA composites
Xicong YE, Chao YANG, Bin OUYANG, Qi GAO, Haihua WU, Enyi HE, Yongsheng YE
2023, 40(2): 911-928. doi: 10.13801/j.cnki.fhclxb.20220415.004
Multi-material composite is an effective method to prepare light-weight, broadband and strong absorbing materials. In this paper, polylactic acid (PLA) was used as the matrix material, and FeSiAl, MoS2 and graphene (GN) were used as fillers. FeSiAl-MoS2-GN/PLA composites, which were used for fused deposition modeling (FDM), prepared by the two-step process of ball milling and melt extrusion. The phase structure, microscopic morphology and electromagnetic properties of composites were characterized by XRD, Raman spectroscopy, SEM and vector network analyzer, respectively. And the effect of graphene content on the electromagnetic wave absorbing properties of composites was also investigated. The research shows that graphene, FeSiAl and MoS2 are randomly dispersed in the PLA matrix and form a complex conductive network; Multi-material composites build rich dielectric/magnetic heterointerfaces, which are beneficial to promote interface polarization; The higher the graphene content, the stronger the electromagnetic wave absorbing properties of composites; When the graphene content is 5wt%, the minimum reflection loss is −27.90 dB at a thickness of 1.7 mm, and the effective absorption bandwidth is 4.96 GHz (12.64-17.60 GHz) at a thickness of 1.9 mm. Its excellent absorbing properties are attributed to the perfect impedance matching and the synergy between dielectric and magnetic losses.
Modified diatomite with enhanced moisture-regulating by surface hydrophobicity and its effect on water vapor permeability of polyurethane film
Xueyan HOU, Hua WEN, Haitao ZHAO, Lihao NI, Yuqi ZHANG, Jijiang WANG
2023, 40(2): 929-939. doi: 10.13801/j.cnki.fhclxb.20220414.001
Waterborne polyurethane (PU) is a kind of environment-friendly coating material, widely used in leather, textile, construction coating and other fields. As a coating for leather and textile, the water vapor permeability (WVP) of polyurethane determines the wearing comfort of clothing. However, the water vapor permeability of conventional waterborne polyurethane is poor and needs to be modified to obtain coatings with excellent WVP. CaCl2 and Heptafluorodecyl trimethoxysilane (FAS-17) were used to modify diatomite to prepare hydrophobic diatomite base materials. The effects of modification conditions on the structure and properties of diatomite were investigated. The modified diatomite with excellent performance was combined with PU emulsion and the WVP of composite film was studied. The results indicate that the diatomite modified with 30wt%CaCl2 and 0.8wt%FAS-17 present the best comprehensive performance with increased specific surface area and pore structure. The moisture-regulating performance is improved and further enhanced by surface hydrophobic modification of FAS-17. After modified diatomite FAS-17-CaCl2-D with best performance is combined with PU, the WVP of FAS-17-CaCl2-D/PU composite film increase first then decrease with the increasing of FAS-17-CaCl2-D dosage, and the hydrophobicity is improved. The composite PU film with 1% of FAS-17-CaCl2-D shows the largest WVP, which increased by 16.3% compared with pure PU film. The SEM-EDS reveal that the the surface and cross section of FAS-17-CaCl2-D/PU composite film appear the characteristic elements of FAS-17-CaCl2-D such as Si, Ca and F. The pores appeared at the interface between PU and FAS-17-CaCl2-D provided channels for the transfer of water vapor, resulting in improved WVP. The WVP enhanced PU in this work are expected to be applied in textile and leather coatings to improve the thermal comfort.
Gas sensing performance and preparation of WO3 nanosheets decorated by ZIF-67
Yanghai GUI, Linlin QIAN, Kuan TIAN, Huishi GUO, Jinghao ZHANG, Chengtao WAN, Xiaoyan YANG
2023, 40(2): 940-949. doi: 10.13801/j.cnki.fhclxb.20220325.003
Metal oxide semiconductor gas sensors are exhibiting great application prospects in the field of toxic and hazardous gas detection gradually, but metal oxide semiconductor sensors are commonly affected by ambient humidity during detection, which significantly limits their applications. In this paper, WO3 nanosheets were successfully in situ grown on the surface of ceramic tubes by hydrothermal method, and ZIF-67 porous materials were grown on the surface of ceramic tubes using it as substrate. Different ZIF-67/WO3 composites were prepared by adjusting the proportion of W and Co. The structures and morphologies of different ZIF-67/WO3 composites were analyzed via XRD, SEM, FTIR and BET techniques. The gas sensing properties of the pristine and different ZIF-67/WO3 composites are investigated. The results indicate that the ZIF-67/WO3(1∶1) composite which W∶Co molar ratio is 1∶1 has the best performance with excellent selectivity to trimethylamine (TEA) at 220℃, and high response of 140.34 to TEA gas with volume fraction of 100×10−6. The response/recovery time is 9 s and 7 s, respectively. The effect of air relative humidity (RH) on the sensors has also studied. The results show that the ZIF-67/WO3(1∶1) sensor can maintain a good response value in an environment humidity up to 75%RH and has a good moisture resistance compared with the pristine WO3 gas sensing material.
Preparation of ZIF-67@PDA/fluorine-containing polyimide mixed matrix membrane and gas separation performance
Jinling LI, Shiqing LAI, Chanjuan LIU, Weilian WU, Jing NI, Xiaohua HUANG, Li ZHOU
2023, 40(2): 950-958. doi: 10.13801/j.cnki.fhclxb.20220406.001
Metal-organic framework (MOF)/polymer mixed matrix membranes (MMMs) have shown great promising application in gas separation fields by combining the features of MOF with molecular sieving effect and polymer matrix with lower cost, better processing properties, and high mechanical strength. However, their applications are greatly limited due to MOF poor dispersity in polymer matrix. The metal frame material ZIF-67 was synthesized by solvothermal method, and the polydopamine (PDA) layer was modified on the surface of ZIF-67 by solution oxidation to prepare ZIF-67@PDA nano-porous materials. The ZIF-67/FPI composite membrane and ZIF-67@PDA/FPI composite membrane with different mass fraction were prepared by using 4, 4'-oxydianiline-2, 2'-(hexafluoroisopropylidene)diphthalic anhydride (ODA-6FDA) fluorinated polyimide (FPI) as matrix and ZIF-67 and ZIF-67@PDA as fillers. The structure and properties of MMMs were characterized by FTIR, WAXD, TGA, SEM, specific surface and pore size distribution analyzer, gas permeant, and the permeability of four gases including N2, O2, CO2, and He was tested. The results show that the nanomicro porous material ZIF-67 modified with polydopamine can disperse uniformly in the polymer matrix and provides fast channels for the passage of gas molecules, and exhibits good thermal stability. ZIF-67@PDA has a good affinity for CO2, which is beneficial to improve the CO2/N2 selectivity. When the ZIF-67@PDA loading is 10wt%, the CO2 permeability and CO2/N2 selectivity of MMMs increases by 131% and 50% respectively compared with pure FPI membrane, and MMMs show good gas separation performance.
Microstructure and corrosion properties of the laser cladding Al-TiC composite coating on AZ31 magnesium alloy
Fenjun LIU, Xiang NING, Yanxia BAI, Zhikang SHEN, Haiyan CHEN
2023, 40(2): 959-969. doi: 10.13801/j.cnki.fhclxb.20220410.002
In order to enhance the surface corrosion resistance of the AZ31 magnesium alloy, the defect-free Al-TiC composite coatings were prepared on AZ31 magnesium alloy using laser cladding technology. The influences of Al-TiC compositions with different contents on the phase composition, microstructure and corrosion resistance of the Al-TiC composite coatings were investigated. The results indicate that a large number of Al12Mg17, Mg2Al3 and TiC phases are produced in the Al-TiC composite coating. The microstructure of the composite coating characterizes as a continuous network distribution. With the decrease of the Al content in the composite powder, the contents of the Al12Mg17, Mg2Al3 and TiC phases in the composite coating gradually increase, and the network-like distribution characteristics of the microstructure in the composite coating become more uniform and continuous. In addition, a sound metallurgical bonding interface is prepared between the composite coating and the AZ31 substrate. The corrosion resistance of the Al-TiC composite coating prepared using the laser cladding technology is significantly enhanced compared to that of the AZ31 substrate. The self-corrosion potential increased from −1.563 V of the AZ31 substrate to −1.144 V of the Al-TiC composite coating, whereas the self-corrosion current decreased from 1.55×10−4 A to 2.63×10−6 A.
Fabrication and application of mesh flexible strain sensor
Liqiang XU, Quan SUN, Zheng ZHAN, Runhong YANG, Zhijie TANG, Yebo LU
2023, 40(2): 970-977. doi: 10.13801/j.cnki.fhclxb.20220804.002
In view of the wide application of strain sensors in human motion monitoring, health monitoring and other fields, it is important to design flexible strain sensors with high sensitivity and large strain range. In this paper, the quadrilateral and hexagonal mesh flexible strain sensors were prepared by template method based on Ecoflex-graphene composites. By comparing the strain range and tensile breaking limit of two different mesh sensors, it is found that the comprehensive performance of hexagonal mesh flexible strain sensor is more excellent, and under the condition of 80% strain, the tensile/releasing fatigue life detection is carried out. The sensor shows good reliability, and the sensor performs well in monitoring the elbow joint movement and different breathing conditions of the human body. A multi-channel detection system was constructed by combining hexagonal mesh flexible strain sensors to realize multiple gesture recognition, which has a broad market application prospect in the field of artificial intelligence and motion recognition.
Civil Construction Composite
Experimental study on flexural performance of ECC beams reinforced with CFRP bars
Jiajia ZHOU, Jinxin WEN, Chuan JING, Jun ZHAO
2023, 40(2): 978-989. doi: 10.13801/j.cnki.fhclxb.20220324.003
To study the flexural performance of engineered cementitious composite (ECC) beams reinforced with carbon fiber reinforced polymer (CFRP) bars, four-point flexural experimental investigates were carried out on three ECC beams reinforced with CFRP bars, one ECC beam reinforced with glass fiber reinforced polymer (GFRP) bars and one concrete beam reinforced with CFRP bars. The main parameters were the reinforcement ratios, the reinforcement type and the matrix type. The experimental results show that the load-deflection curves of ECC beam reinforced with CFRP bars are similar with the ECC beam reinforced with GFRP bars and concrete beam reinforced with CFRP bars, which have an elastic stage, a working stage with cracks and a failure stage. The reinforcement ratio has a great influence on the flexural performance of ECC beams reinforced with CFRP bars. With the increase of reinforcement ratio, the ultimate bearing capacity of ECC beams is improved, and the ductility performance is gradually weakened. The excellent strain-hardening ability and ductility of ECC materials make the ultimate bearing capacity and deformation of ECC beams with CFRP bars superior to the concrete beam reinforced with CFRP bars. Based on the multi-cracking ability of ECC, the strain distribution on the surface of longitudinal bars is more uniform than that of concrete beams with CFRP bars after cracking. Due to the bridging effect of polyvinyl alcohol (PVA) fiber, a large number of fine cracks appear on the surface of ECC beams reinforced with CFRP bars. When ECC beams reinforced with CFRP bars fail, it could maintain good integrity and self-recovering ability. In service stage, the maximum crack width of reinforced ECC beams presents smaller than that of concrete beams. Finally, a simplified calculation model for ultimate bearing capacity of ECC beams reinforced with fiber reinforced polymer (FRP) rebars is proposed, predicting good agreement with the experimental results.
Study on calculation method of RC beam's shear bearing capacity of CFRP grid-polymer cement mortar
Bo WANG, Yuanyuan WANG, Zhengpeng WANG, Junlei ZHANG, Tiansong WANG
2023, 40(2): 990-1003. doi: 10.13801/j.cnki.fhclxb.20220419.004
In order to reveal the shear mechanism of the carbon fiber reinforced polymer (CFRP) grid-polymer cement mortar (PCM) shear reinforced reinforced concrete (RC) beam and establish its bearing capacity calculation method, four-point bending tests and finite element simulation were conducted on the RC beams. The shear contribution of the CFRP grid to the RC reinforced RC beam was analyzed, and the shear bearing capacity calculation method was established based on the improved truss arch model. The results show that the CFRP grid-PCM reinforcement layer can not only inhibit the development of inclined cracks, but also improve the shear bearing capacity. CFRP grid and reinforcement have good cooperative working performance, where the horizontal CFRP grid shares about 16% of the stirrup strain. Regression analysis indicates that the strain of the vertical CFRP grid is about 0.29 times than that of the horizontal CFRP grid. Comprehensively considering the dowel action of the longitudinal CFRP grid and the stirrup strain shared by the horizontal CFRP grid, the bearing capacity calculation method is presented based on the improved truss-arch model, which has better applicability and accuracy to meet the design requirements.
Low-velocity impact properties of carbon/aramid hybrid fiber reinforced corrugated sandwich structure
Tao XI, Aiqing NI, Xiaomei ZHANG, Xiang LI, Jihui WANG
2023, 40(2): 1004-1014. doi: 10.13801/j.cnki.fhclxb.20220317.001
The carbon/aramid hybrid fiber reinforced composite laminates were used here as skins to design corrugated sandwich structures, which were fabricated by vacuum assisted resin infusion (VARI) process. Low-speed impact tests were conducted by three levels of energy, 60 J, 80 J and 100 J, and compression after impact tests were then carried out on these structures. Later, non-destructive testing techniques, including ultrasonic C-scan and industrial CT tomography, were applied to analyze the damage mechanism. The effects of hybrid modes on the low-speed impact properties and post-impact residual compression strength of the structures were investigated. The results show that at lower impact energy, the energy absorption of the corrugated sandwich structures is basically not affected by the fiber stacking sequence of the skins, but the dent depth decreases with the increase of carbon-fiber layers on the surface. By increasing the impact energy, the corrugated sandwich structure with inter-layer hybrid skins exhibits better impact performance because fiber fracture and interlayer delamination mainly occur between the external layers but larger damage area. On the other hand, the corrugated sandwich structure with sandwich-like hybrid skins can absorb more energy by penetration of the skins in small area. In conclusion, better post-impact compression capacity can be achieved for carbon/aramid hybrid fiber reinforced corrugated sandwich structures by the adoption of inter-layer or sandwich-like hybrid skin designs.
Chloride ingress behavior of recycled aggregate concrete subjected to sustained compressive loading and drying-wetting cycles
Jiuwen BAO, Yunwei WANG, Xinyu MOU, Peng ZHANG, Zihao YU, Tiejun ZHAO
2023, 40(2): 1015-1024. doi: 10.13801/j.cnki.fhclxb.20220321.002
The chloride attack environment with cyclic drying-wetting ratio of 3 : 1 and 5wt% mass fraction of NaCl solution was simulated to conduct the chloride ingress test of recycled aggregate concrete (RAC) with diffe-rent replacement rates (r=0%, 30%, 50%, 100%) subjected to sustained compressive loading and drying-wetting cycles. Effect of different sustained compressive stress levels (λc=0.1, 0.3, 0.5) the chloride ingress performance of RAC was studied. Based on the chloride convection-diffusion model of unsaturated concrete, the models of water diffusivity and chloride diffusion coefficient considering the effects of recycled coarse aggregate replacement rate and stress level were proposed and validated. The results indicate that at the same replacement rate of recycled coarse aggregates, the free chloride content, chloride diffusion coefficient and surface chloride concentration in RAC decrease first and then increase with the increase of sustained compressive stress level. Under the same stress level, they are positively correlated with the replacement rate of recycled coarse aggregates. The chloride diffusion coefficients of specimens with the replacement rate of 100% subjected to 0.1fc, 0.3fc and 0.5fc (fc means the cubic comprssive strength of RAC) are 0.97, 0.88 and 1.48 times than that of unstressed state, respectively. The established model of the chloride ingress in RAC under sustained compressive loading and drying-wetting cycles can partly provide the theoretical basis for the durability of RAC.
Hardening mechanism and pore size analysis of new magnetic epoxy cement grout
Jie LIU, Zheng LI, Zhao LI, Tao SUN, Qifen CHENG, Shifu QIN
2023, 40(2): 1025-1036. doi: 10.13801/j.cnki.fhclxb.20220324.002
Conventional mortar can not meet the engineering filling requirements of anti-inclined fractures and defects, and a large number of bubbles will be introduced under the pressure of grouting, and the density of slurry can not be guaranteed. In view of this, a new magnetic epoxy cement (MEC) slurry was developed, which can realize anti-gravity grouting anchoring, guided flow, increase of slurry density and real-time control of slurry viscosity. The SEM,XRD and N2 adsorption tests were used to analyze the microstructure, hydration products and pore size of MEC slurry under different magnetic fields. The results show that the MEC slurry can be divided into the following two hardening processes: Epoxy curing and cement hydration. The solidified product encapsulate the hydration product and ionize with Ca2+ in ettringite (AFt) and Ca(OH)2 to form a complex to fill the tiny pores in the slurry. When the magnetic field intensity increases from 400 GS to 6000 GS, the pore area and pore number decrease rate reach 77.6% and 76.8% respectively. The test of N2 adsorption shows that the number of mesopores and macropores and the specific surface area decrease significantly with the addition of magnetic field. The magnetic grout is in line with H4 hysteresis loop and mainly represents as ink bottle pores. Based on magnetic dipole theory, the force of magnetic particles is simulated numerically. The analysis results show that the pore area can be effectively reduced when the magnetic field intensity is from 2000 GS to 6000 GS.
Biological and Nano-composite
Performance and mechanism of Cr(VI) removal by sludge-derived biochar loaded with nanoscale zero-valent iron
Taotao ZENG, Haidu NONG, Haichao SHA, Shengbing CHEN, Xiaoling ZHANG, Jinxiang LIU
2023, 40(2): 1037-1049. doi: 10.13801/j.cnki.fhclxb.20220324.001
Chromium-containing wastewater was generated in electroplating, metallurgy, printing and dyeing industries, which caused environmental pollution. The sludge-derived biochar (SB) was obtained from the pyrolysis of municipal sludge, and then loaded with nanoscale zero-valent iron (nZVI) to prepare sludge-derived biochar loaded with nanoscale zero-valent iron (nZVI-SB) for the removal of Cr(VI) from water. The effect of the iron to carbon mass ratio, initial pH value, dosage and temperature on the removal of Cr(VI) were explored. SEM-EDS, XRD and XPS were used to characterize the mechanisms of Cr(VI) removal. The results show that nZVI-SB has a desirable removal capacity for Cr(VI). Under the conditions of dosage 0.5 g/L, pH=2 and 40℃, the maximum adsorption capacity of Cr(VI) is 150.60 mg/g by nZVI-SB(1∶1) with a mass ratio of 1∶1 between Fe and SB. The Cr(VI) removal process can be fitted by Langmuir adsorption isotherm and pseudo-second-order kinetic equations. The removal mechanisms of Cr(VI) mainly include adsorption, reduction and co-precipitation. The present study confirms SB and nZVI can synergically remove Cr(VI).
Development and analysis of a novel collagen-sodium humate composite hydrogel
Zhenhua TIAN, Jingxuan HE, Ying WANG
2023, 40(2): 1050-1059. doi: 10.13801/j.cnki.fhclxb.20220321.005
Hydrogel was one of main materials for medical dressings due to the excellent performance such as high elasticity, high water content, cold effect, strong moisture retentiveness and variable shape. Collagen (COL) had good biocompatibility and can promote cell proliferation. And Sodium humate (NaHA) possessed hemostatic, anti-inflammatory and other biological functions. Therefore, a novel collagen-sodium humate composite hydrogel was prepared by mixing collagen and NaHA at various COL∶NaHA ratios and collagen self-assembly, which was expected to be applied as medical dressing. Then the interaction between collagen and NaHA and the microstructures and properties of composite hydrogels were investigated. The collagen triple helix is not affected, although hydrogen bonds and electrostatic interaction occur between collagen and NaHA. At COL∶NaHA≤4∶6, the hydrogels possess good compatibility due to the shielding effect of NaCl on electrostatic binding; however, the coagulation takes place with the further increase in NaHA content. At COL∶NaHA=4∶6, the percentage of NaHA incorporated into collagen fibrils is highest and 93.2%, and the compatibility between collagen and NaHA is good; therefore, the properties of composite hydrogel consisting of mature fibrils with D-periodicity are optimum. Moreover, about 80% of NaHA still remain in hydrogel, indicating its release is slow. The thermal stability improves by 34.9°C, and storge modulus and loss modulus are 31.89 Pa and 3.99 Pa, respectively. Furthermore, the pore sizes of the lyophilized composite hydrogels decrease and the pores become dense and well-distributed. The composite films have significant rises in hydrophilicity.
Preparation of high-strength and low-temperature-resistant nanocellulose/polyvinyl alcohol conductive composite hydrogel and its application in flexible sensing
Kui HU, Yingyue WANG, Haoyu WANG, Zhipeng ZHAO, Kai LIU, Liulian HUANG, Lihui CHEN
2023, 40(2): 1060-1070. doi: 10.13801/j.cnki.fhclxb.20220322.003
Nanocellulose is an excellent nano-reinforcing material with large aspect ratio, high elastic modulus and specific surface area, and abundant surface functional groups. Nanocellulose (cellulose nanofibers, CNFs) was first used as the dispersion medium to disperse the MXene nanosheets for preparing the nanocellulose/MXene nanocomposites, and the interaction between nanocellulose and MXene was characterized and analyzed by FTIR and XPS. Then the CNF-MXene/PVA composite hydrogel was prepared by using the CNF-MXene nanocomposites as the reinforcing filler and polyvinyl alcohol (PVA) as the matrix, which was further treated with KOH solution to improve the mechanical properties of the composite hydrogel and endow the composite hydrogel with excellent ionic conductivity. The composite hydrogel exhibites excellent mechanical properties, the tensile strength and elongation at break were 22.5 kPa and 1098.2%, respectively. The hydrogel also possesses high conductivity (2.38 S/m), anti-freezing, and excellent strain/pressure responsive properties. Thanks to the extremely low detection limit (100 mg) and extremely fast response time (225 ms), the hydrogel-based strain/pressure sensor could monitor the pressure changes causes by pulse beating and small vibration of throat. Therefore, the composite hydrogel-based flexible sensor showes great promising applications in the next-generation wearable electronics and human-machine interaction.
Manganese-nitrogen co-doped rice husk biochar activated peroxydisulfate to degrade acid orange
Shiyuan HUANG, Senhuan LIN, Wen DONG, Guohua WANG, Xingliang WU, Hanqin YUAN
2023, 40(2): 1071-1084. doi: 10.13801/j.cnki.fhclxb.20220328.001
In order to better deal with the problem of azo dye (acid orange, AO7) dye pollution in water environment, Mn and N co-doped biochar composites (Mn-N-BC) were prepared by pyrolysis method using rice husk, urea and manganese salt as raw materials, and acid orange (AO7) dye wastewater was degraded by activated peroxydisulfate (PDS). The effects of initial AO7 concentration, PDS concentration, catalyst dosage and initial pH value on the removal rate of AO7 were investigated. The results show that the Mn-N-BC/PDS system has a high removal rate of AO7 dyes, which can reach 98.6% in 30 min, its apparent rate constant kobs is 0.125 min−1; and shows high resistance to inorganic anions in the water environment. After three times of recycling, the removal rate of AO7 is still about 75%, indicating that Mn-N-BC has high reusability and stability in the removal of organic pollutants. Free radical quenching and XPS analysis showed that the degradation mechanism of AO7 in Mn-N-BC/PDS system included free radical pathway (•OH, SO4•) and non-free radical pathway (O2•, 1O2 and electron transfer), in which non-free radical pathway was the main role.
Bionic design of wood cell wall based on 3D printing
Shiqi QIN, Zechun REN, Chenxi WANG, Yun KOU, Zhaoyan LIU, Min XU
2023, 40(2): 1085-1095. doi: 10.13801/j.cnki.fhclxb.20220414.004
Cellulose, which plays the role of skeleton in wood, exists in the cell wall in the form of microfibrils with different helical structures. In this paper, the fiber spiral reinforced structure of wood cell wall was studied by combining 3D printing technology with simulation. Using microcrystalline cellulose (MCC)/polylactic acid (PLA) composites, based on the testing of the properties of MCC/PLA composites, the spiral structure of wood cell wall was constructed with the help of 3D printing technology, and the mechanical function of the structure was programmed by changing the fiber orientation and fiber pore structure. Finite element simulation was used to emphasize the key role of fiber in the load transfer mechanism between rigid elements. The results show that the properties of the structure can be controlled by programming the orientation and structure of the fiber, and the cross structure of the fiber can be used to improve the mechanical properties of the structural molded products as an optimal design. These structures can be assembled into larger systems for building modular composites with optimized specific functions. It has potential application value in the field of hetero structure design and new composite material manufacturing.
Preparation and mechanical properties of multi-walled carbon nanotubes-bacterial cellulose composite films
Cuiyu TIAN, Zhaoqing LU, Doudou NING, Ruixia ZHAO, Bo GENG
2023, 40(2): 1096-1104. doi: 10.13801/j.cnki.fhclxb.20220512.002
Exploiting and utilizing green biomass materials can reduce the consumption of petroleum-based polymers. However, compared with the single bacterial cellulose (BC), BC film always exhibits the poor mechanical properties, which limits its application. In this study, in order to improve the strength and toughness of BC composite films synergistically, BC was treated by alkaline and 2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPO) oxidation to obtain TEMPO-oxidized BC (TOBC), which was utilized as matrix to prepare the TOBC-based composite films enhanced by carboxylic multi-walled carbon nanotubes (CNT) via vacuum filtrating technique. The effect of CNT amounts on the mechanical properties and microstructure of TOBC-based composite films were investigated emphatically and the strengthening and toughening mechanism was also discussed. The results show that: When CNT content is 7.5wt%, CNT-TOBC composite films exhibit the best mechanical properties. The tensile stress, elongation and toughness of CNT-TOBC-7.5wt% composite films are 174 MPa, 10.83% and 12.01 MJ·m−3, respectively, which are increased by 56.76%, 144.47% and 295.07% compared with the pure TOBC films, respectively. The improvement is attributed to the hydrogen bonding interaction between CNT and TOBC, the high strength of CNT, as well as the external toughening mechanism. This study provides a feasible method to improve the interface bonding and mechanical properties of composites, and further broadens the application of TOBC in flexible electronic substrates, intelligent packaging and other fields.
Metal and Ceramic Matrix Composite
Effect of interfacial reaction on wear properties of Cu35Ni25Co25Cr15 multi-principal components alloy/diamond composites
Yang GAO, Haibo XIAO, Yong LIU, Wei ZHANG
2023, 40(2): 1105-1117. doi: 10.13801/j.cnki.fhclxb.20220331.004
Diamond superhard abrasive tools play an increasingly important role in high-end chips, 3C ceramics processing and other fields. The interface between binder phase and diamond greatly affects the mechanical and wear properties of diamond superhard composites. In order to study the interfacial bonding between binder phase and diamond, Cu35Ni25Co25Cr15 multi-principal components alloy/diamond composite was prepared by spark plasma sintering (SPS). The interfacial reaction between alloy binder phase and diamond particles was studied by thermodynamic calculation and experiments. The results show that chromium reacts with diamond at the interface to form Chromium carbides. Moreover, with the sintering temperature increasing, the thickness of Chromium carbides layer grows and the cohesion coefficient between the alloy binder phase and diamond increases. When sintering temperature reaches 950℃, the Chromium carbides layer is uniform and continuous, and the thickness is about 1.1 μm. The friction and wear tests show that on the surface of the composite sintered at 900℃ and 950℃, the alloy binder phase is removed firstly by the shear stress, and then the diamond particles expose. Due to the retention of the Chromium carbides layer, the grinding performance of the composites is improved effectively. Therefore, appropriate interfacial reaction improves the service properties of the diamond composites.
High-temperature compressive properties of 20vol% volume fraction nano-Al2O3 particles reinforced aluminum matrix composite
Xuan LI, Ke ZHAO, Jinling LIU
2023, 40(2): 1118-1128. doi: 10.13801/j.cnki.fhclxb.20220401.001
To improve the high-temperature mechanical properties of aluminum-based materials with the aim of satisfying application requirements for the structural components in aerospace above 573 K, a novel aluminum matrix composite reinforced with 20vol% volume fraction nano-Al2O3 particles (146 nm) was prepared via high energy ball milling followed by vacuum hot pressing, and its microstructures and high-temperature compressive properties were investigated. The results show that, nano-Al2O3 particles are uniformly distributed in the ultrafine-grained Al matrix, and the resultant composite is fully densified. The composite exhibits superior high-temperature compressive properties: As the strain rate is fixed as 0.001/s, the high-temperature compressive strength reaches 380 MPa at temperature of 473 K, still maintains a high value of 250 MPa when the temperature increased to 673 K, which is at least onefold higher than that of traditional Al-based materials. By establishing constitutive model based on thermal activation, it is also found that the composite shows high stress exponent which is 30 and high apparent activation energy which is 204.02 kJ/mol. This may be attributed to the addition of high volume fraction nanoparticles into Al matrix which not only anchors Al grain boundaries and enables thermal stable interface between nanoparticles and the Al matrix and thus significantly enhance the thermal stability of the microstructure, but also can impede the dislocation motion effectively as well as Al grain boundary, thereby increasing the threshold stress for hot deformation which ranges from 190.6 MPa to 328.4 MPa as the temperature is in the range of 473 K to 673 K. The hot deformation process of this composite can be properly explained by substructure invariant model.
Composite Micro-mechanics
Micro-mechanics analytical method for composite out-of-plane wrinkle with double fiber-waviness
Mei LU, Yile HU, Yin YU
2023, 40(2): 1129-1141. doi: 10.13801/j.cnki.fhclxb.20220317.002
Composites are widely used in aerospace industry because of their outstanding advantages, such as high specific modulus, high specific strength and long fatigue life. However, composite often encounters wrinkle defects in the manufacturing process. The existence of wrinkle defects has negative impacts on the stiffness and strength of composite laminates. The mechanical properties of composites with wrinkle of single and double fiber-waviness were studied in this paper. Analytical and numerical methods were used to calculate the effective material properties of single and double fiber-waviness wrinkle with micro-mechanical models. Through the comparison and analyses of the prediction results from micro-mechanical models, it is shown that when the absolute value of waviness ratio increases, the effective modulus of the laminate with wrinkle decreases. When the absolute value of waviness ratio is the same, the effective modulus of the laminate with concave wrinkle is lower than that with convex wrinkle. There is an intersection point among the effective modulus curves obtained from wrinkled laminates with different thicknesses. The variation of effective modulus associated with laminates thickness is opposite on the two sides of intersection point. The intersection point of wrinkle with double fiber-waviness is different from that of single fiber-waviness.
Prediction of in-plane tensile strength of needle punched C/C composites
Wentai LIU, Kun CHENG, Helezi ZHOU, Xia BAI, Dunming LIAO, Huamin ZHOU
2023, 40(2): 1142-1153. doi: 10.13801/j.cnki.fhclxb.20220310.001
In order to study the in-plane tensile strength and the progressive damage behavior of needle punched carbon fiber reinforced carbon composites (needle punched C/C composites), a representative volume element finite element model of needle punched C/C composites was established. The model was divided into four sub-regions: non-woven cloth, short cut fiber felt, needling fibers and interface, and the effect of pores was estimated. Based on the failure criterion and exponential damage evolution law, the damage of the non-woven cloth and needling fibers was studied. The damage of the short cut fiber felt was defined by an elastic-plastic constitutive method. A cohesive force traction separation law and a quadratic nominal stress criterion were adopted at the interface. The negative influence of pores on mechanical properties of the material was considered by two steps. Then, mechanical properties of the four sub-regions were calculated. The in-plane tensile stress-strain curve of the material was predicted through ABAQUS UMAT subroutine, and the damage initiation, propagation and failure of the four sub-regions were simulated. The nonlinear trend and tensile strength agree well with experimentally measured data, which verifies the proposed model.
Numerical study on the effect of void content on hygrothermal performances of carbon fiber reinforced polyamide 6 composites
Yongpeng LEI, Zhenhang KANG, Zhu LIU, Quanwei SONG, Jifeng ZHANG
2023, 40(2): 1154-1166. doi: 10.13801/j.cnki.fhclxb.20220318.001
Voids are comment defects generated during the manufacturing process and highly sensitive to moisture in the hygrothermal environment. The presence of voids will change the stress field and moisture field, which has deleterious effects on the mechanical performances. The mechanical properties of carbon fiber reinforced polyamide 6 (CF/PA6) composites after hygrothermal aging under different temperature immersion environment were tested to study the effects of temperature and water absorbed content on the mechanical properties. The correlation function between water content and mechanical parameters was established. Based on the random sequential adsorption algorithm (RSA), the representative volume element (RVE) model with random distribution of fibers, interfaces and voids was established. The quantitative effects of voids content on strength and modulus under the loading of transverse tension, compression and shear were investigated, by introducing a degradation factor dependent on water content into the constitutive model, and the failure mechanisms before and after hygrothermal aging were revealed. Conclusively, before hygrothermal aging, voids induce the decrease of mechanical properties due to stress concentration, and every 1% increase in the voids content results in a 6.4% decrease of transverse tensile strength. However, matrix degradation due to the absorbed water content after hygrothermal aging is the dominant factor, and the corresponding rate is 3.86%.
Tensile bearing behavior of composite structures considering filament wound morphology
Lei XIAO, Haixiao HU, Dongfeng CAO, Weihua LEI, Tao JI, Shuxin LI
2023, 40(2): 1167-1178. doi: 10.13801/j.cnki.fhclxb.20220419.010
Fiber bundles of filament wound structure have the morphology characteristic of crossover and undulation, which has significant impact on the mechanical behavior of composite structures. In this research, the tensile mechanical behavior of filament wound composite plate was investigated by numerical and experimental methods. In experimental study, quasi-static tensile experiment of fiber-wound composite plate was carried out, and the evolutions of surface strain field were recorded by digital imaging correlation (DIC). The influences of crossover and fluctuation characteristics on the load-displacement curve and strain distribution were investigated. For the numerical analysis, a meso-scale finite element model was created based on the filament wound morphology. The progressive failure process was simulated based on 3D Hashin failure criterion, and the nonlinear shearing behavior of composites was also involved. The experimental and numerical studies of laminated structures were also carried out as the reference group. The experimental results indicate that, compared with the laminated structures, the filament wound structure gives a lower stiffness, a larger failure displacement, and almost a same failure load. An obvious strain concentration is observed in the fiber crossover and undulating region which locates at the middle area of the filament wound rhombus unit. The finite element analysis results are in good agreement with the experimental ones. The strain concentration in the fiber fluctuation region, as well as the failure initiation and propagation behaviors, are represented properly by the numerical analysis.
Deformation control in shape machining of CFRP flexible parts
Youliang SU, You LI, Zhijian MENG, Qingbin WANG, Xuenan GAO, Jian HU
2023, 40(2): 1179-1189. doi: 10.13801/j.cnki.fhclxb.20220322.002
The shape machining of carbon fiber reinforced polymer (CFRP) flexible parts is an important process in manufacturing of high-end aerospace equipment. Reliable clamping of the flexible parts is a prerequisite to control the deformation and reduce the dimensional deviation in machining. Firstly, the basic conditions for clamping and friction constraint by theory analysis were given, and a principle of “Following the shape and near the point” for the sucker distribution based on the cantilever beam theory was proposed. Furthermore, based on the “ISIGHT-ABAQUS” co-simulation method, the simulation analysis of the deformation of the CFRP flexible part were taken under different clamping conditions. The research shows that the elastic deformation of the vacuum sucker is easy to increase the clamping deformation, and the combination of the vacuum and positioning suckers should be used. When the numbers of the positioning suckers are 8, 12, or 16, and are distributed according to the principle of “Following the shape and near the point”, the influence of the distribution of the vacuum sucker on the deformation of the flexible part is negligible. Finally, the machining size deviation when considering the positioning geometric deviation was analyzed by the simulation and experiment. The trends in simulation and experiment are consistent with each other, and after the clamping optimization the dimension deviation can be reduced by 57.7 μm (35%). In summary, the machining dimension deviation caused by the deformation in shape machining of CFRP flexible parts cannot be ignored, and then the clamping optimization under the proposed principles of “Following the shape and near the point” and “Combining of positioning and vacuum suckers” can greatly reduce the dimension deviation caused by the deformation.
Structural design and low speed impact performance of cross recessed grid sandwich
Zhongliang CAO, Hao ZHU, Mingjun DONG, Qing HE
2023, 40(2): 1190-1207. doi: 10.13801/j.cnki.fhclxb.20220311.001
Aiming at the problems of low ultimate bearing capacity of traditional grid sandwich structure and easy condensation of water vapor caused by single cell sealing, a cross-locked grid sandwich structure was proposed based on analyzing the microstructure and function of tracheids. Firstly, the minimum volume (minimum mass) and minimum deformation (maximum stiffness) were selected as the optimization objectives, and the second generation non-dominated genetic algorithm (NSGA-II) was used to complete the multi-objective optimization. The three-dimensional Hashin failure criterion and the improved stiffness degradation method were used to establish the finite element analysis model of progressive impact damage for the grated sandwich plate. The failure mechanism and mechanical response of a variety of low speed impact loads to different positions of sandwich structures with different relative densities were studied. Results show that the new type of sandwich structure shows good shock impedance at low speed. Its differences with the core of the spatial distribution, the shock resistance of grille gaps are weaker. Core density increase cannot effectively improve the impact strength of the location. The sandwich structure is much larger than all the damage by impact grid intersection point of the device. Under the influence of different impact location and impact velocity, load-time and displacement-time curves show different typical patterns. The failure of core appears, such as buckling, delamination, bonding stripping and bending deformation, and mixed damage occurs on the front panel of composite material. With the increase of impact velocity, the damage degree of core and panel becomes more serious.
Prediction of anisotropic coefficient of thermal expansion for laminated composite using multiscale numerical models
Pei WAN, Hui XIA, Chen LIU, Jilong JIA, Xue HE, Anxin DING
2023, 40(2): 1208-1217. doi: 10.13801/j.cnki.fhclxb.20220331.001
Representative volume element (RVE) in lamina and laminate levels were build based on the arrays of fiber into resin and stacking sequences in laminated composites. In combination with the specified boundary conditions in RVE models, coefficient of thermal expansions (CTEs) and engineering constants for lamina were predicted, followed by an evaluation of anisotropic CTEs for laminate using multiscale method. The results show that numerically predicted CTEs match well with experimental data as compared to theoretically calculated value as a whole, especially for the numerically predicated CTEs of unidirectional T300/5208, P75/934 and C6000/Pi carbon fiber reinforced epoxy resin matrix composites with a difference of 3%, 1% and 2%, respectively. And the predicted engineering constants using RVE model for unidirectional ECR/Derakane 510C glass fiber reinforced vinyl ester resin matrix composites were also in good agreement with experimentally measured results, with a maximum difference of 7.5%. Meanwhile, the difference between experimental results and forecasted CTEs in through-thickness direction for cross-ply AS4/8552 carbon fiber reinforced resin matrix composites using RVE model of laminated composites is nearly negligible with a difference of 0.08%. Finally, the equivalent CTEs of laminated composite with different stacking sequences were estimated using RVE models of lamina and laminate levels for cross-ply composite structures in large large-scale structures, and the results reveal that CTEs in through-thickness direction are weakly related to the ratio of stacking sequences in hoop direction.
Compression failure life prediction and verification of polymethacrylimide foam
Haoyu MENG, Bo CHEN, Jiang SONG, Chaoming SUN, Chenglei YAN, Xin AN, Tao ZHANG
2023, 40(2): 1218-1228. doi: 10.13801/j.cnki.fhclxb.20220314.003
Polymethacrylate imide (PMI) foam is widely used in aerospace field because of its superior performance. This paper mainly studies the functional characteristics of PMI foam in the field of cartridge adapter, and mainly studies its compression creep characteristics at room temperature. According to the working conditions and creep characteristics of polymer materials, the "time strengthening" model was adopted to design experiments, and the PMI foam with densities of 0.075 g/cm3 and 0.110 g/cm3 were respectively tested for 180 days under normal temperature compression creep. By analyzing and fitting the experimental data, the compression creep life of two PMI foam with different densities at room temperature and 1250 N was predicted. The compression creep failure life of PMI foam with density of 0.075 g/cm3 is about 11 years. The density of 0.110 g/cm3 PMI foam is about 53 years, and the reliability of the model is verified and analyzed.