2020 Vol. 37, No. 12

Recent advances in understanding environmental effects on degradation of carbon fiber/epoxy matrix interface in civil engineering applications via molecular simulation
Chao WU, Ruidong WU, Jinqiao JIANG, Lik-ho TAM
2020, 37(12): 2941-2952. doi: 10.13801/j.cnki.fhclxb.20200831.003
In civil engineering, carbon fiber-reinforced polymer (CFRP) composite has been increasingly used in building structures, due to its excellent mechanical properties. The interface between carbon fiber and epoxy matrix is critical for the stress transfer in the CFRP, which largely determines the long-term durability of composite material. However, the fiber/matrix interface is vulnerable to the hygrothermal and salt environment, which leads to the interfacial debonding and final composite failure. In consideration of the durability issue of composite material, the interfacial degradation between fiber and matrix under environmental effects should be fully understood. Molecular dynamics simulation can provide a bottom-up description of the fiber/matrix interface in the simulated environments, which contributes to the understanding of the interfacial degradation mechanism. In this work, the recent simulation progress in understanding the environmental effects on the degradation of carbon fiber/epoxy matrix interface from a nanoscale perspective was reviewed, including the development of the interface model, the degradation of the interfacial structure and properties in various environments such as wet and salt environment, and the underlying degradation mechanism. Meanwhile, future research direction involving further development of the fiber/matrix interface model was also provided.
Research progress of nano-hydroxyapatite and its composite materials as drug carriers
Ying LU, Xiaowei XUN, Zhiwei YANG, Honglin LUO, Yizao WAN, Guifu ZUO
2020, 37(12): 2953-2965. doi: 10.13801/j.cnki.fhclxb.20200814.002
Nano-hydroxyapatite (HAp) is an ideal inorganic drug carrier due to its good biological activity and drug adsorption ability. In this paper, the drug loading performance of nano-HAp was described by three aspects: Biological safety, antitumor activity and drug adsorption. Moreover, the effect of HAp micromorphology on drug-loading performance was also discussed. Furthermore, the classification, preparation, drug loading and drug release of nano-HAp composites were systematic reviewed, which aimed to provide a theoretical basis for application as drug carrier of nano-HAp and its composites.
Research progress for the composite sandwich structure with foldcore
Yunfei DENG, Xianzhi ZENG, Xiang ZHOU, Xiangqian LI, Jian XIONG
2020, 37(12): 2966-2983. doi: 10.13801/j.cnki.fhclxb.20200903.001
The composite sandwich structure with foldcore is a new type of structural material with light weight, high specific strength, high specific rigidity and multi-functional potential, which is connected with each other in core space. This kind of three dimensional structures can be formed by folding based on two dimensional materials. The main research achievements and characteristics of composite sandwich structure with foldcore in recent years are summarized and analyzed according to the lightweight and multi-functional requirements of aircraft structure in this paper. The configuration optimization scheme and fabrication process of the composite sandwich structure with foldcore are described. Moreover, the research status of mechanical properties and multi-function of the composite sandwich structure with foldcore are summarized, including the quasi-static mechanical properties, impact resistance, sound insulation, thermal protection, stealth performance of the structure, etc. Based on the research status, it provides suggestions for the research possible direction of the composite sandwich structure with foldcore in future.
Research progress of Ti-based MXene and its composites in metal-ion batteries
Hao LIU, Weitang YAO
2020, 37(12): 2984-3003. doi: 10.13801/j.cnki.fhclxb.20200717.001
Since two-dimensional transition metal carbides (nitrides or carbonitrides) MXenes was first reported in 2011, its family members have been increasing. At present, more than 20 MXenes have been successfully synthesized. With unique layered structure, excellent physicochemical properties and designable surface functional group characteristics, MXenes are considered as promising electrode material. In recent years, some remarkable progress of MXenes and its composite materials are achieved in energy storage. To this end, this review presents the research progress of Ti-based MXenes and its composite materials in Lithium-ion batteries and Sodium-ion batteries. Combined with the preparation methods and characteristics of MXenes, the strategies or mechanisms of improving battery performance are introduced in detail. Finally, the challenges and prospects of MXenes and its composite materials in fabricating high-performance batteries are pointed out.
Research progress of new carbon based magnetic composite electromagnetic waveabsorbing materials
Min CAO, Yuxi DENG, Kang XU, Xiaofeng HAO, Jiayu HU, Xi YANG
2020, 37(12): 3004-3016. doi: 10.13801/j.cnki.fhclxb.20200825.002
New carbon based magnetic composite absorbing materials have become the mainstream of electromagnetic wave absorbing materials because of their light weight and high performance. Carbon based wave absorbing materials have the advantages of low density, large specific surface, high conductivity, but also have the disadvantages of non-magnetic and low impedance matching level. They are often combined with magnetic loss materials to build light composite materials with various microstructures and multiple cooperative loss mechanisms to achieve efficient and broadband electromagnetic waveabsorption. On the basis of summarizing the research on the wave absorbing application of carbon matrix composites at home and abroad, this paper analyzes the research progress of new graphene, carbon nanotubes, biomass porous carbon and other carbon matrix magnetic composite wave absorbing materials with composition, composite method and microstructure as the main line, and finally points out the existing problems and future development trend of carbon based magnetic absorbing materials.
Resin Matrix Composites
Preparation and properties of polyethylene terephthalate filter material with superhydrophobic surface
Wei DONG, Fuping QIAN, Qing LI, Tengfei XIANG, Tiejun CHUN, Jinli LU, Yunlong HAN, Yongjun XIA, Jia HU
2020, 37(12): 3017-3025. doi: 10.13801/j.cnki.fhclxb.20200421.003
Superhydrophobic polyethylene terephthalate (PET) filter was prepared by sol-gel method with PET filter as matrix material, tetraethyl orthosilicate (TEOS) and methyl triethoxysilane (MTES) as modifiers. Field emission scanning electron microscopy (FESEM-EDS), Fourier transform infrared spectrometer (FTIR) and contact angle measurement were introduced to investigate the micro morphology, surface composition and contact angle of PET filter material before and after modification. The results show that the porosity of the filter material is slightly changed after modification. TEOS-modified PET (T-PET) filter material shows superhydrophilic due to the formation of a large numbers of hydrophilic —OH groups. On the contrary, hydrophobic —CH3 groups are existed on the surface of MTES modified PET (M-PET) filter material, which endows high hydrophobicity. Moreover, TEOS and MTES modified PET (MT-PET) filter material displays superhydrophobicity due to lots of SiO2 nanoparticles covered by —CH3 groups are deposited on the fiber surface, reducing the surface energy of the filter material and forming micro-nano, wrinkled and even convex structure. MT-PET presents static contact angle (WCA) of (158.8±1.2)° with water shedding angle (WSA) of (6.9±1.5)°, indicating superhydrophobic state of MT-PET filter material. In addition, through the contrast test of spraying wet dust and soaking filter material in water (room temperature), it shows that MT-PET filter material has good self-cleaning performance and stability. In conclusion, the preparation of superhydrophobic MT-PET filter material in this paper has potential value for the research and development of bag filter material in high humidity environment.
Preparation and properties of bacterial cellulose-ZnO/waterborne polyurethane composite films
Jing WU, Wei ZENG, Meixia KUANG, Cheng ZHONG
2020, 37(12): 3026-3034. doi: 10.13801/j.cnki.fhclxb.20200407.001
Bacterial cellulose-ZnO (BC-ZnO) composite particles were prepared through the hydrothermal synthesis method using BC as a template, using Zinc sulfate、NaOH and urea as raw materials. The results show that BC-ZnO composite particles are the novel brush-like structure with a size of 3-5 μm. BC filaments are wrapped in brush-like ZnO at a level of approximate 19wt%. The formation mechanism of the brush-like structure of the composite particles is explained. Bacteria cellulose-ZnO/waterborne polyurethane (BC-ZnO/WPU) composite film was obtained by introducing different contents of BC-ZnO composite particles into waterborne polyurethane by in-situ polymerization method, and the structure and performance of the composite film were characterized. SEM shows that composite particles are well dispersed in polyurethane. The properties reach the optimal when the proportion of BC-ZnO is 1.0wt%, the tensile strength is 84.6% higher than that of pure WPU; the water absorption is deceased from 16.5% to 4.9%; the addition of BC-ZnO improves the initial thermal stability of the composite film; the composite film shows good antibacterial properties. When the BC-ZnO content is 1.3wt%, the antibacterial rate against S. aureus exceeds 99% and the antibacterial rate against E. coli exceeds 85%.
Preparation and characterization of a silicon-containing arylacetylene resin with cyano groups
Manping MA, Niping DAI, Chuan LI, Xiaotian LIU, Qiaolong YUAN, Farong HUANG
2020, 37(12): 3035-3042. doi: 10.13801/j.cnki.fhclxb.20200507.003
A silicon-containing arylacetylene resin with cyano groups (CNSA resin) was formed by reaction of 2,6-bis-(4-ethynylphenoxy)-phenylnitrile polymerized with dimethyldichlorosilane by the catalysis of anhydrous zinc trifluoromethane sulfonate at room temperature. The structure and properties of the CNSA resin were characterized by 1H-NMR, FTIR, DSC and TGA analysis techniques. The results show that the CNSA resin has good solubility and a wide processing window. The curing reactions of the CNSA resin take place at low temperature (<200℃). The cured CNSA resin has good heat resistance. There is no glass transition in the temperature range of 50−400℃. The decomposition temperature of 5% mass loss Td5 is 512℃ in nitrogen. The flexural strength and the flexural modulus of T300 carbon fiber cloth/CNSA (CF/CNSA) composites are 383.8 MPa and 62.9 GPa at room temperature, respectively.
Continuous fabrication of flexible, thermally conductive aluminum nitride/aramid nanofiber composite films
Fanzhan ZENG, Xianhong CHEN, Jianfeng WANG
2020, 37(12): 3043-3051. doi: 10.13801/j.cnki.fhclxb.20200428.001
Designing and preparing flexible thermally conductive materials is important for thermal management of flexible electronic devices. Based on exfoliated aramid nanofiber and aluminum nitride (AlN) nanoparticle, flexible and thermally conductive composite films were fabricated by a sol-gel-film transformation approach. In the composite films, aramid nanofibers forms three-dimensional connective network for providing mechanical support. AlN nanoparticles are filled in the network of aramid nanofiber to impart the composite films with good thermal conduction performance. As a result, the tensile strength and strain at break are 65.5 MPa and 12%, respectively. After folding for 300 cycles, the composite films retain more than 90% of original tensile strength and strain at break. The thermal conductivity is up to 13.98 W·(m·K)−1. Moreover, the composite films show good electrically insulating property and thermal stability. The volume electrical resistivity and initial thermal decomposition temperature are 1.85×1015 Ω·cm and 524℃. Finally, we demonstrate that the high-performance AlN/aramid nanofiber composite films can be act as flexible substrate for cooling electronics.
Flexural behavior of glass fiber reinforced polymer tube filled with steel bars/concrete hollow members
Ni ZHANG, Chenyang ZHENG, Li’na XIAN, Lianguang WANG
2020, 37(12): 3052-3063. doi: 10.13801/j.cnki.fhclxb.20200417.001
In order to study the flexural performance of glass fiber reinforced polymer (GFRP) tube filled with steel bars/concrete hollow members, a nonlinear analysis program was developed. The effects of main parameters such as hollow rate, reinforcement ratio, GFRP tube wall thickness and strength grade of concrete were analyzed systematically. The program was verified by test. The calculation formula of the bearing capacity of GFRP tube filled with reinforced hollow concrete members was established. The results show that the calculation results are in good agreement with the test results by using the nonlinear analysis program and the established bearing capacity formula. The flexural bearing capacity increases with the decrease of the hollow rate and the increase of the reinforcement ratio, the GFRP tube wall thickness and the concrete strength grade. The hollow rate has the greatest influence on the flexural bearing capacity, followed by the reinforcement ratio and the thickness of GFRP tube wall thickness, and the concrete strength grade has relatively less influence on the flexural bearing capacity. The radius ratio of hollow part should be 0.25-0.5. The flexural bearing capacity of the hollow members can be compensated by properly increasing the reinforcement ratio, GFRP tube wall thickness or concrete strength grade. The research conclusion can provide reference for the practical application of the GFRP tube filled with steel bars/concrete hollow member structure.
Experimental analysis of the causes of skin wrinkles below the radius filler of hat-stiffened skins
Dongliang ZHANG, Xiangchen XUE, Xianzhu LIANG, Lihua ZHAN, Xiaobo YANG, Xiaoling ZHENG
2020, 37(12): 3064-3070. doi: 10.13801/j.cnki.fhclxb.20200323.002
The formation process and causes of the skin wrinkles under the radius filler were studied in the co-bonding process of the hat-stiffened skins of carbon fiber/epoxy resin composite with the pre-cured stiffener and uncured skin. The rheological properties of the resin of the prepreg were tested. The internal pressure distribution of the skin under the radius filler was monitored by pressure monitoring equipment, and the wrinkles were characterized by metallographic microscope. The results show that during the window period of the resin flow, the resin flows to the low-pressure area and aggregates, resulting in wrinkles when a pressure difference occurs inside the skin under the radius filler.
Properties of cyanate ester resin for hot melt prepreg
Xiaomeng HUO, Fan WANG, Zhuojun YAO, Jingbin DAI, Yaping ZHU, Huimin QI
2020, 37(12): 3071-3078. doi: 10.13801/j.cnki.fhclxb.20200506.001
PM915 resin was prepared by modifying cyanate ester resin with polyethersulfone (PES). The processability and cured resin properties of PM915 resin were investigated systematically. The PM915 resin has excellent process performance, good film-forming property and better storage stability, and could be used to prepare prepreg by hot melting method. The process properties such as rheological property and gel time of PM915 resin were measured. The results show that the viscosity of PM915 resin at 70℃ is about 20 Pa·s, the viscosity of the resin can keep stable for 115 min at 120℃, and the gelation time is 40 min at 160℃. Due to the release of some reaction heat in the preparation process, the curing exothermic enthalpy of PM915 resin decreases, and the curing temperature of PM915 resin is 220℃. The curing shrinkage of PM915 resin is as low as 0.16% due to the introduction of PES. The temperature at 5% thermal weight loss Td5, glass transition temperature Tg and thermal expansion coefficient of cured PM915 resin are 423℃, 276℃ and 4.4×10−5/℃, respectively, which indicates that the cured PM915 resin possesses excellent thermal properties. After modification, the toughness of the cured resin has been greatly improved owing to the introduction of flexible groups. The flexural strength and modulus of the cured PM915 resin are 139.3 MPa and 4.2 GPa, the tensile strength and modulus of the cured PM915 resin are 75.8 MPa and 3.8 GPa respectively. What’s more, the investigation of fracture surface by scanning electron microscope (SEM) indicates that the cured PM915 resin exhibits toughness fracture. Therefore, the PM915 resin is a kind of ideal resin matrix for fiber reinforced prepregs by hot melting process, and possesses low curing shrinkage, high dimensional stability and heat resistance, which can be used in satellites and other spacecraft.
Adhesion of SiO2-methyl vinyl silicone rubber molecular interface modified by silane coupling agents
Chengjiang WANG, Zhengyang FAN, Ning ZHAO, Wenji ZHOU
2020, 37(12): 3079-3090. doi: 10.13801/j.cnki.fhclxb.20200609.002
Nano-SiO2 doping has become an effective way to improve the performance of methyl vinyl silicone rubber (MVSR). However, nano-SiO2 is easy to agglomerate. When it is directly mixed into MVSR matrix, nano-SiO2 is difficult to disperse in MVSR matrix, resulting in poor adhesion effect of SiO2-MVSR molecular interface, defects in the molecular interface and other adverse effects, so that the purpose of improving MVSR performance cannot be achieved. In order to improve the adhesion of SiO2-MVSR molecular interface and make nano-SiO2 more easily dispersed in MVSR matrix, this paper constructed the SiO2-MVSR molecular interface models that unmodified and modified by KH550, KH560, KH570 and KH792, and carried out structural optimization and molecular dynamics calculation. By comparing the adhesion energies, adhesion depths and adhesion thermal stabilities of the molecular interface in different models, the reason for the improvement of the adhesion of SiO2-MVSR molecular interface modified by silane coupling agents was analyzed from the perspective of molecular structure. The results show that the key to improve the adhesion of SiO2-MVSR molecular interface is to select the non-hydrolytic group of the silane coupling agents. When the proportion of the same chemical bond between the non-hydrolytic group and MVSR molecular chain is larger, and the number of more electronegative atoms is more, the effect of improving the adhesion of SiO2-MVSR molecular interface is better. At the same time, the longer chain length and larger relative molecular weight of silane coupling agent will also help to improve the adhesion.
Effect of low temperature exposure on tensile mechanical properties of carbon fiber/epoxy composites
Jian LUO, Jianjun SHI, Bin JIA, Jun MO, Hui HUANG
2020, 37(12): 3091-3101. doi: 10.13801/j.cnki.fhclxb.20200629.001
According to the effects of low temperature exposure on the mechanical properties of carbon fiber/epoxy (CF/EP) composites, the tensile properties of TR50S/YPH-69 were selected after low temperature of 0℃, −20℃, −40℃, −60℃ for 100 h, 200 h, 300 h, 400 h and 500 h to investigate the effects of low temperature, then the damage mechanism of material was analyzed by SEM. Based on the test results, a prediction formula was proposed to predict the residual strength of CF/EP composites exposed at low temperature. The test results present that after experiencing long time cryopreservation, the tensile mechanical properties of CF/EP composites increase first and then decrease, with the increase of the low-temperature exposure time. When the exposure time at low temperature is less than 300 h, the tensile strength of CF/EP composites increases first and then decreases as the temperature decreases; after the exposure time exceeds 300 h, the tensile strength gradually decreases as the temperature decreases. And the tensile elastic modulus of CF/EP composites shows a gradual upward trend with the increase of low-temperature exposure time, the lower the temperature, the more obvious the upward trend. SEM analysis shows that after a short period of low temperature exposure, the fiber and epoxy resin bond stronger, which is conducive to load transfer and enhance the CF/EP composites’s tensile ability, the destruction morphology is represented by more resin wrapped on the fiber. After long-term exposure to low temperature, material may occur cracks due to different contraction coefficient. Under the applied load, the crack gets further spread, which is not conducive to the load transfer, and causes the tensile strength to decline. The failure morphology shows that the fibers agglomerate into bundles, and the fiber bundle spacing increases. Based on initial test, a formula of predicting the residual strength of CF/EP composites after low temperature exposure was proposed. The test results are in good agreement with the predicted results. The number of tests can be reduced, due to consider the equivalent effect of the same material under different low temperatures and exposure time.
Tunable mechanical and acoustic properties of anisotropic magnetic polyurethane foams with different carbonyl iron powder magnetic particle contents
Caiping WANG, Jiahua ZHANG, Xiaojie WANG
2020, 37(12): 3102-3110. doi: 10.13801/j.cnki.fhclxb.20200401.001
Polyurethane foams (PUFs) have been widely used in aircrafts, vehicles and many other facilities for noise control. Magnetic polyurethane foams (MPUFs) are a new kind of smart foams whose mechanical and acoustic properties can be controlled by magnetic fields. In this paper, the anisotropic MPUFs was studied which were prepared by one-step full water foaming method with carbonyl iron powders (CIPs) magnetic particles. During the foaming process, the magnetic field was applied, and the CIPs were arrayed into a chain-like structure along the direction of the magnetic field. The movement of CIPs inside MPUFs under the magnetic field induces a change towards the mechanical and sound absorption properties. The influence of the external magnetic field on the mechanical properties and sound absorption properties of CIPs/MPUFs was investigated by experiments. The results show that under the magnetic field, the storage modulus and loss modulus of CIPs/MPUFs increase with the increase of CIPs content. The variation of the average sound absorption coefficient is between 1% and 7%. For the sample with 5wt% CIPs foamed under 200 mT, the increment of its average sound absorption coefficient under 1.5 A is 6.5%, which is maximum.
Based on dry blending method to control the micro-cracks morphology of metal film on flexible template
Bo TIAN, Xiangdong YE
2020, 37(12): 3111-3118. doi: 10.13801/j.cnki.fhclxb.20200319.002
Using 500 nm SiO2 nanoparticles as a filler and polydimethylsiloxane (PDMS) as a polymer coated with nanoparticles, a novel dry blending method was used to prepare the SiO2/PDMS flexible template with SiO2 nanoparticles as high as 83.8wt%. The flexible template has an elastic modulus (E) of 16.58 MPa and a thermal expansion coefficient (CTE) of 96×10−6/°C, compared with the pure PDMS flexible template by direct incorporation of SiO2 and PDMS in wet blending, which increases by 91.56% and decreases by 69.23%, respectively. The flexible template has good transparency. Finally, a silver film was deposited on the surface of the flexible template by magnetron sputtering, and the surface morphology of the silver film was characterized by SEM and AFM. The results show that the surface of the silver thin film is smooth and the roughness is small, the silver thin film has good stability. Effectively suppression the micro-cracks formation of metal film on the flexible template prepared by the dry blending provides a new solution for the manufacture of good conductivity electrodes and large-area metal film.
Discrete conductivity modeling method for plain weave carbon fiber reinforced resin composites
Ronghua ZHANG, Keyu SHI, Shuo LI, Yifan ZHANG
2020, 37(12): 3119-3127. doi: 10.13801/j.cnki.fhclxb.20200327.001
The electrical impedance distribution of carbon fiber reinforced resin composites (CFRP) with weaving technology has the characteristics of anisotropy, heterogeneity and complex geometric structure. Establishing the electrical impedance distribution model is the key joint to obtain the defect and fatigue damage information of CFRP in the braiding process by using electromagnetic eddy current nondestructive testing technology. Based on the theory of electrical impedance tensor modeling, the method of characterizing the electrical characteristics of the multi-layer braided structure CFRP two-dimensional plane was established, and a simplified electrical impedance distribution model of the braided CFRP was established, thereby realizing the accurate and fast finite element analysis of the electromagnetic properties of the braided CFRP. Based on the finite element simulation, the electromagnetic nondestructive testing of plain weave CFRP was designed by designing a dual-air rotating coil electromagnetic sensor. The polar coordinate chart of the impedance was used to describe the impedance change trend of the measured material in different directions. The correctness of the finite element modeling was proved by experiment. Finally, the proposed modeling method was used to simulate the detection effect of the double air rotating coil sensor on the structural defects and cyclic load fatigue of the plain weave CFRP.
Metal and Ceramic Matrix Composites
Preparation and photocatalytic properties of FeVO4/Cu3(BTC)2(H2O)3 heterojunction
Yingqi LIU, Wenbin WENG, Qin CEN, Wei XIAO, Qi WANG, Yanqing CONG, Yi ZHANG
2020, 37(12): 3128-3136. doi: 10.13801/j.cnki.fhclxb.20200917.001
The classic Cu-MOF material Cu3(BTC)2(H2O)3, which was also named HKUST-1, was prepared by electrochemical method using Cu flakes and 1, 3, 5-benzenetricarboxylic acid as the raw materials. Furthermore, the FeVO4/HKUST-1 heterojunction composites were prepared by room temperature deposition using HKUST-1 as the base metal organic framework material (MOFs). The crystal structure, morphology, specific surface area and optical absorption properties were characterized by XRD, SEM, BET, UV-Vis DRS, etc. The results indicate that the formation of the heterojunction between FeVO4 and HKUST-1 is beneficial for the generation and transfer of the photogenerated electron-hole pairs. The degradation performance of target dye pollutant rhodamine B (RhB) is significantly enhanced. After visible light irradiating for 120 min, the degradation efficiency to RhB can reach 93% in the heterojunction system, while only 12% and 5% can be observed in the system of FeVO4 or HKUST-1, respectively. In addition, the composition ratio of the composite was also optimized. When the molar ratio of FeVO4 to HKUST-1 is 1∶1, the as-prepared FeVO4/HKUST-1 composite has the best photocatalytic performance. Furthermore, the stability was investigated. After 5 cycles, the degradation efficiency to RhB is still above 90%, indicating good stability of the FeVO4/HKUST-1 composite.
Tailoring of interface reaction, microstructure and compressive properties of graphene reinforced titanium alloy matrix composites
Juan WANG, Faming ZHANG, Caiyun SHANG, Bin ZHANG
2020, 37(12): 3137-3148. doi: 10.13801/j.cnki.fhclxb.20200421.001
Few-layered graphene reinforced titanium matrix composites (GR/TC4) with 3D network structures were fabricated through a 3D mixing machine and spark plasma sintering (SPS) technique. The effects of different sintering temperatures, holding time, heating rate and uniaxial pressure in the SPS on the in-situ interface reaction of GR with titanium matrix were studied. The phases, microstructure and compressive properties at room temperature of the network structured composites with different GR/TiC ratios were investigated systematically. Experimental results exhibite that the SPS temperature and heating rate are the key factors for determination of reaction ratio of the GR with matrix and the uniaxial pressure affects relative density of the composites. Low temperature, high pressure and fast sintering can inhibit the reaction between the GR and matrix. However, the composites with more residual GR do not show excellent mechanical properties. It is indicated that excellent compressive strength and ductility integrated mechanical properties are achieved with GR reaction ratio of 70%-80% in the 0.25wt% GR/TC4 composites, where the interface bonding is to an optimal state. The 3D network distribution of GR in the titanium alloy matrix can tailor the conflict between strength and ductility of the titanium matrix nanocomposites.
Free vibration characteristics of corrugated sandwich plates under different boundary conditions
Wenhao YUAN, Fenglian LI, Mei LV
2020, 37(12): 3149-3159. doi: 10.13801/j.cnki.fhclxb.20200414.001
As a special composite structure, the vibration characteristics of corrugated sandwich panel are greatly influenced by the boundary conditions. According to the shear deformation theory of different shear modes and Kirchhoff's classical plate theory(CLPT), the dynamic equation of corrugated sandwich plates was established by Hamilton principle. Among them, the corrugated core layer was equivalent to an anisotropic homogeneous body. According to the boundary conditions of four sides simply supported, four sides clamped, opposite sides simply supported and clamped, one side fixed and three edges clamped, the partial differential dynamic equation relative to the displacements was derived. By solving the equation, the natural frequencies of the corrugated sandwich plates under different boundary conditions were obtained. Compared with the finite element simulation results, the correctness of the theoretical results was verified. On this basis, based on the exponential shear deformation theory(ESDT), the variation of fundamental frequency of the corrugated sandwich plate with material parameters and structural geometric parameters under different boundary conditions was analyzed. The results show that the material and structural geometric parameters have an important influence on the vibration characteristics of the corrugated sandwich plates under different boundary conditions. Relevant research results will provide a theoretical basis for the vibration reduction design and optimization analysis of corrugated sandwich plates in engineering application.
Preparation of poly 3,4-ethylenedioxythiophene/nanoporous gold composite electrode and its application in supercapacitors
Yunqiang YANG, Jiali ZHANG, Haixia ZHANG, Ying HOU
2020, 37(12): 3160-3167. doi: 10.13801/j.cnki.fhclxb.20200403.001
The poly 3,4-ethylenedioxythiophene/nanoporous gold (PEDOT/NPG) composite electrode materials were prepared by electrochemically polymerizing monomer 3,4-ethylenedioxythiophene (EDOT) onto NPG with high conductivity and large specific surface area by one-step method. The scanning electron microscope (SEM), transmission electron microscope (TEM), Raman spectroscopy (Raman) and X-ray energy spectrometer were used to analyze the morphological structure and elemental composition of the composite electrode material. The electrochemical performance of the electrochemical workstation was studied systematically. The PEDOT/NPG electrode material has a mass specific capacitance of 555 F/g at low current density of 3 A/g, and its energy density and power density are 177.58 W·h/kg and 1.73 kW/kg, respectively. The electrode material can still maintain 91.5% of the maximum capacitance after 2 000 cyclic voltammetry test and has excellent electrochemical performance.
Formation mechanism of diamond/Ti interface based on vacuum hotpressing diffusion method
Jiandong YUAN, Aibing YU, Lei SUN, Yanlin WANG, Jianying CHI
2020, 37(12): 3168-3176. doi: 10.13801/j.cnki.fhclxb.20200519.001
With the vacuum hot pressing diffusion method, Ti coating layer was prepared on the surface of polycrystalline diamond to investigate the formation mechanism of the interface during diamond metallization. The surface morphology, interface structure and phase composition of the Ti coating layer were analyzed with a scanning electron microscope and an X-ray diffractometer. The interfacial elements were analyzed with an energy disperse spectrometer. The width of the element diffusion zone between polycrystalline diamond and Ti layer and the free enthalpy change for the chemical reaction to generate TiC were calculated. The research results show that flat and dense Ti layer is formed on the surface of polycrystalline diamond. There is diffusion of carbon, Ti and cobalt elements on bonding interface between Ti coating layer and polycrystalline diamond. An element diffusion zone with a certain width is generated on bonding interface. At the same time, spot-shaped TiC particles are formed on diamond surface. The vacuum hot pressing diffusion method can realize a chemical combination between diamond grain and a Ti layer, and can improve the bonding strength between diamond grain and Ti layer.
Preparation and photocatalytic properties of TiO2/electrospinning PAN-based carbon composite material
Xiang YU, Xueyin ZHANG, Ruyang LI, Yahao ZHAO, Xiaolong LU
2020, 37(12): 3177-3183. doi: 10.13801/j.cnki.fhclxb.20200429.001
To enhance the photocatalysis and recycling abilities of catalyst simultaneously, polyacrylonitrile (PAN) and tetrabutyltitanate (TBT) were used as carbon-nanofibers (CNFs) and TiO2 precursors, and TiO2/CNFs composite materials were successfully prepared via electrospinning and heat treatment, and its morphology, crystal structure, optical performance and photocatalytic properties were studied by SEM, XRD, Raman, UV-vis Spectrophotometer and so on. The results show that the crimp shape of the composite material gradually disappears during heat treatment, and TBT is completely transformed into anatase TiO2 during carbonization with the increase of TBT content. The absorption edge of TiO2/CNFs composite material is extended from the ultraviolet region of pure TiO2 to visible, which can improve the utilization of sunlight. At the same time, after simulated solar irradiation for 180 min, the maximum photocatalytic degradation rate of RhB by TiO2/CNFs composite material reaches 95.71%. Moreover, the photocatalytic degradation efficiency can still reach about 90% after repeated useage for 5 times.
Preparation of modified microcrystalline cellulose based composite and its catalytic degradation performance on methylene blue
Jiachuan CHEN, Dexian JI, Zhaoyun LIN, Guihua YANG, Huimin HOU
2020, 37(12): 3184-3193. doi: 10.13801/j.cnki.fhclxb.20200416.001
Microcrystalline cellulose (MCC) was used as raw materials and loaded with CuO nanoparticles (CuO NPs). Then, 3-chloropropyltrimethoxysilane (CPTES) and diethanolamine (DEA) were added for grafting reaction to prepare CuO NPs@MCC–Si–N(OH)2. CuO NPs@MCC–Si–N(OH)2 was characterized with FTIR, XRD, thermal gravimetric analysis and morphology analysis. The results show that CuO NPs can be successfully loaded on the surface of MCC, and silane coupling agent can improve the dispersion of the composite and the ability to graft amine groups, thus enhancing its catalytic activity, and increasing the redox reaction efficiency of sodium borohydride (NaBH4) and methylene blue (MB). Hence, MB stain is degraded rapidly. It’s also found that CuO NPs@MCC–Si–N(OH)2 with 20wt% DEA shows the best catalytic effect, and the highest removal efficiency is 99.71% after treating 30 mL MB solution (3 mmol/L) with 30 mg CuO NPs@MCC–Si–N(OH)2 and 10 mg NaBH4 within 5 min, and the removal rate is 93.24% after five cycles.
Effect of folded contact between electrode and dielectric layer on the performance of piezoelectric flexible electronic skin
Jintong ZHANG, Gang ZHOU, Guiting CHEN, Congkang XU, Jiangyong WANG
2020, 37(12): 3194-3200. doi: 10.13801/j.cnki.fhclxb.20200416.002
A simple method for fabricating flexible electronic skin based on piezoelectric effect was presented. In order to study the effect of nano modification on the performance of flexible electronic skin, SiO2/polydimethylsiloxane (PDMS) composite flexible substrate was prepared by using nano-SiO2 particles as modifiers and PDMS as matrix. The flexible and stable electrodes were prepared and the crack problem of electrode material on flexible PDMS substrate by magnetron sputtering was successfully solved. The functional layer of barium titanium trioxide/carbon nanotubes/PDMS (BaTiO3/CNTs/PDMS) was implanted in the five-layer structure of the flexible electronic skin that was designed based on the piezoelectric effect. A simple method by varying the substrate roughness was proposed to make a folded contact between the electrode and the dielectric layer. This method improves the conductivity and piezoelectric response of the prepared flexible electronic skin.
Experimental study on shear behavior of steel fiber-rubber/concrete
Qiuhong ZHAO, Shuo DONG, Han ZHU
2020, 37(12): 3201-3213. doi: 10.13801/j.cnki.fhclxb.20200507.005
Shear strength and toughness are important indices for evaluating load-resisting capacity and energy absorption of members under complex loading conditions. In order to study the shear-resisting capacity of high-strength steel fiber(SF)-rubber/concrete, 14 sets of SF-rubber/concrete specimens were designed for double-shear experiments, in which influence of parameters including SF volume fraction, rubber volume substation and water to binder ratio on the shear-resisting behavior and failure modes of SF-rubber/concrete were investigated. Research results show that the bridging action of SF and its positive synergy with rubber particles in SF-rubber/concrete can significantly improve the shear-resisting behavior of concrete. SF play a dominant role in shear-resisting behavior of SF-rubber/concrete specimens. The shear strength, deformation at peak load and shear toughness of SF-rubber/concrete specimens are significantly higher than the plain concrete and rubberized concrete specimens, which increase with the SF volume fraction, and the shear failure mode of SF-rubber/concrete is obviously ductile. When the SF volume fraction is 1.5vol% and the rubber content (volume substitution of sand) is 10%, the shear strength and deformation at peak load of SF-rubber/concrete specimens are 78% and 63% respectively, higher than those of the rubber concrete. Rubber particles also help to improve the shear-resisting behavior of SF-rubber/concrete. The shear toughness and ductility of SF-rubber/concrete are further increased compared with SF reinforced concrete. With the increase of rubber content, the shear strength, peak deformation and pre-peak shear toughness of SF-rubber/concrete can be unchanged after using the optimized water-binder ratio, while the post-peak toughness index can be further increased by 96%. Based on the test results, shear strength formula of SF-rubber/concrete was established considering the influence of SF volume fraction and rubber substitution.
Longitudinal scale effect of electro-thermal effectiveness of front panel of the integrated wooden electric heating composite based on carbon fiber paper
Yongjie BAO, Chengjian HUANG, Yuhe CHEN, Yueping DAI
2020, 37(12): 3214-3219. doi: 10.13801/j.cnki.fhclxb.20200402.001
Based on laws of thermodynamics: law of conservation of energy and Fourier law, the theoretical relationship between the structure property and the environment temperature above the surface of the integrated wooden electric heating composites based on carbon fiber paper (CFP) was derived with the solution for one-dimensional heat transfer problem, and then qualitatively analyzed to study the longitudinal scale effect of the front panel of the integrated wooden electric heating composites. The derived relational expression shows an inversely proportional relationship between the structure property and the environment temperature. In order to verify the theoretical calculation results, the temperature tests were conducted on the integrated wooden electric heating composites with 2 mm and 4 mm thickness front panel respectively. The results show that the relationship between the thickness of the front panel and the air temperature above the surface of the composites based on CFP presents inversely proportion based on the mathematical calculation. Compared with the air temperature above the surface of composites with 4 mm thickness front panel, the air temperature of the composites with 2 mm thickness front panel turns out to be higher through experimental validation, which is consistent with the theoretical calculation. Hence, the integrated wooden electric heating composites with thinner front panel have an advantage of utilization of energy.
Tensile stress-strain relationship of engineered cementitious composites reinforced by high-strength stainless steel wire mesh
Xinling WANG, Guanghua YANG, Wenwen QIAN, Ke LI, Juntao ZHU
2020, 37(12): 3220-3228. doi: 10.13801/j.cnki.fhclxb.20200428.002
In order to study the tensile performance of the engineered cementitious composites (EEC) reinforced by high high-strength stainless steel wire mesh, the parameters of reinforcement ratio of high-strength stainless steel stranded wire, tensile strength of ECC and width of ECC reinforced by high high-strength stainless steel wire mesh specimen were considered, and the uniaxial tensile tests of total of 27 test pieces were carried out. The test results show that the cracking stress and ultimate stress of the specimens increase with the increase of the steel strand reinforcement ratio and ECC tensile strength. The crack stress and ultimate stress of the specimens are almost not affected by increasing the width of the specimen. Based on the test results, the tensile constitutive model of high-strength stainless steel stranded wire mesh reinforced ECC and the formulas for calculating the cracking stress and ultimate stress were proposed. It is proved that the calculated results are in good agreement with the experimental results, which indicates that the established tensile constitutive model can accurately describe the tensile stress-strain relationship of ECC reinforced by high-strength stainless steel wire mesh.
Functional element topology optimization method based on multiple evaluation points for metamaterial design with zero Poisson’s ratio
Deqing YANG, Shan ZHONG
2020, 37(12): 3229-3241. doi: 10.13801/j.cnki.fhclxb.20200306.001
The functional element topology optimization method based on multiple evaluation points was proposed to design metamaterial with zero Poisson’s ratio. The zero Poisson’s ratio effect of a cell was achieved through multiple evaluation points that defined positive and negative Poisson’s ratio constraints in one topological ground structure. Topology optimization models were established by minimal mass and maximal compliance objective functions, and corresponding functional element configurations with zero Poisson’s ratio were optimized and designed, which were similar to semi re-entrant hexagonal honeycomb. The optimal functional element configurations were extracted and periodic arranged as metamaterial structure with zero Poisson’s ratio. The finite element method (FEM) was used to verify the Poisson’s ratio of these functional elements. The static and dynamic characteristics of metamaterial structures were also analyzed through finite element models. The results show that the metamaterial structure based on maximal compliance objective has better in-plane specific stiffness and vibration isolation performance, and its Poisson’s ratio is closer to zero compared with minimal mass objective model. The structures of double-layered cylindrical shells with conventional solid ring-rib and zero Poisson’s ratio metamaterial ring-rib were designed, and the analysis under static pressure from outer shell and underwater radiation noise caused by internal equipment were conducted. By converting the compression deformation of the outer shell into the rotation of the inner shell, the zero Poisson’s ratio metamaterial ring-rib achieves shape conservation of the inner shell. The metamaterial ring-rib can also reduce the underwater radiation noise from cylindrical shell.