COMPOSITES SCIENCE AND ENGINEERING

Preparation, structure and properties of high strength carbon aerogel composites

SHEN Zehui, CAO Yu, HAO Jingying, ZHANG Qikai, NIU Bo, ZHANG Yayun, LONG Donghui

2024, 0(6): 5-14. DOI: 10.19936/j.cnki.2096-8000.20240628.001

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Aiming at the thermal bridge blocking demand of thermal protection system, carbon aerogel composites with medium-density and high strength were prepared by sol-gel, atmospheric pressure drying and high temperature carbonization processes using carbon/quartz fiber hybrid needle-punched preforms as reinforcement and phenolic resin as carbon precursor, and the microstructure, mechanical properties and thermal insulation performance of the composites were systematically investigated. The results show that the composites has strong mechanical properties (compressive stress approximately 10 MPa at 5% compressive strain) and excellent thermal insulation properties (room temperature thermal conductivity <0.230 W·m^-1·K^-1) with medium density (approximately 0.80 g·cm^-3). As the mass fraction of quartz fibers in the preform increases from 0% to 20%, the equivalent thermal conductivity of the composite decreases from 0.224 W·m^-1·K^-1 to 0.158 W·m^-1·K^-1 at 1 000 ℃, indicating the potential for high-temperature thermal bridge-blocking applications. Further, the lattice Boltzmann method was used to predict the thermal conductivity of the material from room temperature to 1 600 ℃, and the trends of the influence of material structure and environmental factors on the thermal conductivity were found. The increase in the porosity of the carbon aerogel matrix leads to the increase in the resistance of heat transfer, which leads to the decrease in the thermal conductivity of the composite. The increase in the density of the preform leads to the increase in the channels for heat transfer, which makes the thermal conductivity of the composite increase. The increase of quartz fiber content leads to the gradual decrease of thermal conductivity of the composites. When the air pressure is low, the thermal conductivity increases rapidly with the increase of air pressure, while when the air pressure is high, the thermal conductivity is almost unaffected.

Study on synthesis, curing kinetics and ceramic product’s properties of SiBCN ceramic precursor

PENG Zhe, YAO Lichao, CHAI Xiaoxiao, LI Song

2024, 0(6): 15-21. DOI: 10.19936/j.cnki.2096-8000.20240628.002

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Four SiBCN precursors with low viscosity were synthesized by dehydrogenation of polysilazane and borazine. The precursor molecular structure, curing kinetics and ceramicized product’s properties of SiBCN precursorswere investigated by fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), ultra-high temperature thermogravimetric analysis (TG), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The results show that four SiBCN precursors are the viscosity of 198~275 mPa·S at room temperature and curing temperature of 120~235 ℃. The curing process of SiBCN precursors make double exothermic peaks. The kinetic parameters of SiBCN precursor P1, P2, P3, P4 are calculated by Kissinger, Ozawa and Crane equations depended on main exothermic peak, where the results are summarized as follows: Apparent activation energy are 96.9 kJ/mol, 88.4 kJ/mol, 119.5 kJ/mol, 268.2 kJ/mol with reaction order of 0.933, 0.930, 0.940, 0.943. The XRD results indicate that the ceramic product of P4 maintains amorphous structure by sintering at 1 300 ℃. The content of B in the ceramic product of P4 is 4.67% and decomposition temperature is higher than 1 650 ℃. The decomposition temperature shows a certain relationship with content of B in ceramic product of SiBCN precursors: The high-temperature stability of the ceramic product is effectively improved when the B content of SiBCN precursor exceeds a certain concentration.

Simulation of thermochemical ablation of modified C/SiC-ZrC composites

ZHANG Chuandian, CHEN Tao, DUAN Zhenyan, LIU Fengyu

2024, 0(6): 22-28. DOI: 10.19936/j.cnki.2096-8000.20240628.003

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Ultra-high temperature ceramic matrix composites prepared based on matrix modification of C/SiC composites are an effective way to meet the higher requirements for thermal protection system materials required by hypersonic aircrafts. The ablation model of C/SiC-ZrC composites is constructed based on thermochemical equilibrium theory, and two sets of C/SiC-ZrC composites with different volume fractions under the same preparation method in the literature were selected, and the dimensionless ablation rates of the two sets of materials were calculated using MATLAB, and then numerical simulations were established in COMSOL multiphysics field analysis software, and the simulation results were compared with the experimental results in the literature, and the errors were 8.7%~16.9% and 1.05%~11.07%, respectively, which verifies the validity of the model.

Study on properties of diamine-type benzoxazine modified bisphenol A epoxy resin and its glass fiber reinforced composites

CHENG Sheng, XIE Zhihui, HE Weihan, ZHANG Yue, LIANG Zhiming, HUANG Ze, ZHANG Wei, RAN Qichao

2024, 0(6): 29-33. DOI: 10.19936/j.cnki.2096-8000.20240628.004

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To extend the shelf life of epoxy resin and enhance its heat resistance, benzoxazine resin can be used for blending modification. Blending resin systems (E/B-x) of epoxy resin (EP) and benzoxazine resin (BZ) with different mass ratios were prepared in solution. Their viscosities, rheological properties, gelation activation energies and curing exothermic peaks were tested and analyzed. After the addition of BZ, the viscosities become low and the gelation activation energies increase, which delays the curing reaction to a certain degree. In addition, the copolymerization reaction was analyzed by FTIR technology. Then, the surface properties of the copolymer were investigated and showed that the water contact angle of the copolymer was gradually increased with the increase of addition of BZ. Furthermore, glass cloth reinforced composites were prepared, and their dry and wet T_gs were obtained by DMA. Compared with EP composite, dry and wet T_gs of E/B-40 composite with 40wt% of BZ increase by 12.6% and 11.7%, respectively. Moreover, its flexural strength and modulus achieve 569 MPa and 27.9 GPa, respectively.

Performance analysis of shape-memory alloy sheet-based actuator with integrated deformation load-bearing intelligent composite structure

ZHAN Yue, YUAN Guoqing

2024, 0(6): 34-40. DOI: 10.19936/j.cnki.2096-8000.20240628.005

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The introduction of pre-strain on the shape memory alloy sheet can produce a heat-reversible sheet actuator, which can be glued to the surface of the composite structure to obtain a smart composite structure with integrated load-bearing and deformation. In this paper, we focus on the deformation of the smart composite structure during the load-bearing process, and analyze the heat-activated deformation capacity during load-bearing and load-bearing capacity after heat-activated deformation of the smart composite structure by means of finite element analysis. The results show that the smart composite structure can still deform smoothly during the load-bearing process, but its deformation capacity and service life are affected by the load. And the stress of adhesive layer during the loading of the thermally actuated process under the same load will be larger compared to the adhesive layer stress during the heating of the loading process.

Research on the overall buckling performance of FRP profiles with hinged metal extruded sleeve joints subjected to axial compression loads

XU Jianghong, ZHANG Dongdong, SHAO Fei, GAO Yifeng, BAI Linyue, LÜ Chenxi

2024, 0(6): 41-47. DOI: 10.19936/j.cnki.2096-8000.20240628.006

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This article focuses on FRP compression profiles with end hinged metal extruded sleeve joints in assembled truss structures. The overall buckling performance of these hybrid members was studied through axial compression tests and finite element methods. The influence of metal joint segments on the critical buckling bearing capacity of FRP profiles of different lengths was revealed by parametric analysis. In addition, based on the experimental and finite element results, the formulas for calculating the global buckling critical bearing capacity of five kinds of FRP profiles commonly used in engineering were compared and verified, and the calculation method suitable for the global critical buckling capacity of such FRP profiles was determined. The results show that compared to FRP profiles without end extruded metal sleeve joints, the FRP tube undergo shear fracture at the end of the metal outer sleeve, rather than at the middle of the FRP tube, i.e., the local structure of the end metal extruded sleeve joints has a significant impact on the failure mode of the FRP compression profiles. The overall critical buckling load of FRP profiles with end metal joints is improved to a certain extent. With the increase of slenderness ratio, the increase of influence of end-metal segment on the critical buckling load of FRP profiles decreases gradually. It is suggested that Engesser or Haringx modified formula can be used as the design formula for FRP compression profiles with end hinged extruded metal sleeve joints.

Effectiveness analysis of carbon fiber reinforced transmission tower angle steel

GUAN Tianyu, JIANG Lan, DUAN Guoyong, TANG Bo

2024, 0(6): 48-59. DOI: 10.19936/j.cnki.2096-8000.20240628.007

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The damaged angle steel of transmission tower is taken as the research object. Based on the reinforcement and repair technology of carbon fiber reinforced polymer (CFRP) at home and abroad, the method of strengthening angle steel with carbon fiber cloth is proposed. In this method, carbon fiber cloth is pasted onto the surface of angle steel by adhesive for reinforcement. There is no secondary damage to angle steel during the reinforcement process, and the process is simple and practical. By establishing a numerical analysis model of composite structures, the effects of carbon fiber cloth reinforcement thickness, reinforcement layer number, ply angle and reinforcement method on the reinforcement effect of composite members are studied. The results show that the relative improvement of the bearing capacity of the angle steel reinforced with carbon fiber cloth will increase. When using four layers of 0.668 mm thick carbon fiber cloth, the improvement of the ultimate bearing capacity of the angle steel can basically meet the reinforcement demand. When the angle of each layer of carbon fiber cloth is laid in the direction of 0° along the axial compression direction of angle steel, the reinforcement effect can be maximized. Combined with economic considerations, the effect of medium-package reinforcement on angle steel is better than that of full-package reinforcement.

Finite element analysis of the compressive properties of weft V-shaped woven spacer composites

LIU Shengjie, SHAO Huiqi, CHEN Nanliang, JIANG Jinhua, ZENG Jinjin, CHEN Junfeng, BAI Yifeng

2024, 0(6): 60-68. DOI: 10.19936/j.cnki.2096-8000.20240628.008

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The failure modes and damage processes of weft V-shaped woven spacer composites were examined under flat and edgewise compression loads. The ABAQUS program was used to create a multi-scale single-cell composite model and define periodic boundary conditions. The elastic characteristics of fiber bundles were studied in order to predict the macroscopic material elastic constants. For the progressive damage analysis of weft V-shaped 3D woven spacer composites, a subsequent improvement of the UMAT subroutine in Fortran provides a 3D Hashin damage criterion and a Camanho stiffness degradation scheme. The results reveal that the simulated and test outcomes are consistent. Under the flat compression stress, the V-shaped pile warp group with higher bending amplitude cracked first, whereas the pile warp group with lower amplitude fractured subsequently, resulting in a secondary peak load. Stress concentrations at the interweaving of the pile warp and weft, as well as at the pile warp’s flexure, with fractures concentrated at the pile warp’s highest flexure and at the interface with the panel, and no obvious panel breakage; the principal load-bearing entities under edgewise pressure are the resin panel and the inner resin yarn, with the top layer of weft yarn under more pressure and the spacer layer of pile warp under less pressure. Fracture occurs mostly between the two rows of V-pile yarns, with gradual resin breakdown, fiber debonding, and yarn breaking as failure modes.

Simulation and experimental study of milling force of helical milling carbon fiber composites

XING Wentao, SUN Huilai, LI Hang, LIU Yu, ZHAO Fangfang

2024, 0(6): 69-75. DOI: 10.19936/j.cnki.2096-8000.20240628.009

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Based on the motion trajectory equation of a single abrasive grain, this paper uses ABAQUS finite element software to simulate the helical milling process, and analyzes the simulation of the stress distribution at the edge of the hole inlet and outlet and the variation law of milling force. During the process of spiral milling holes in carbon fiber reinforced plastic (CFRP), the variation law of milling force and the influential degree of different process parameters on milling force are studied. Subsequently, an orthogonal experiment for spiral milling was designed, using range analysis to study the experimental results and comparing them with the simulation results to determine the accuracy of the simulation results. The results show that the spindle speed is negatively correlated with the axial milling force, and F_x is minimal at 3 500 r/min. The rotational speed and pitch are positively correlated with the milling force. The revolution speed is the main factor affecting the tangential milling force, while the spindle speed and pitch are the secondary factors. The revolution speed is the main factor affecting the axial milling force, while the pitch and spindle speed are the secondary factors.

Strain response and numerical modelling study of FRP partially confined concrete columns based on finite element and DIC tests

JI Yongcheng, ZOU Yunfei

2024, 0(6): 76-86. DOI: 10.19936/j.cnki.2096-8000.20240628.010

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Fibre reinforced polymer (FRP) partially confined concrete applications can improve the load-bearing capacity and economic value of concrete. However, the response of FRP partially confined concrete to inhomogeneous strains in the vertical direction is not sufficiently well developed and the stress-strain model is not sufficiently accurate. In this paper, axial compression tests are first carried out on FRP partially confined concrete by means of strain gauges and digital image correlation (DIC) records. In addition, partially confined concrete including 0/1, 1/4, 1/3, 1/2, 2/3, 3/4 and 1/1 confined area ratios are established using ABAQUS finite elements. The experimental results show that the DIC and strain gauge results respond to the strain patterns in the vertical and horizontal directions respectively, i.e. the specimens undergo significant strain localisation in either strain hardening or strain softening response; the finite element results were able to capture the surface restraint force of the specimen with respect to the x, y and z-axis strains, and the stress-strain relationships were obtained for FRP partially restrained concrete columns with different restraint area ratios, and the proposed stress-strain model was able to have a high predictive effect.

Research on vibration damping performance of high-damping composite drive shaft based on viscoelastic material

WEN Xianglong, HE Zhenzhong, ZANG Meng, SONG Chunsheng, ZHANG Jinguang

2024, 0(6): 87-94. DOI: 10.19936/j.cnki.2096-8000.20240628.011

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Carbon fiber reinforced plastics (CFRP) have excellent comprehensive material properties and have been widely used in the fabrication of various primary and secondary load-bearing parts in recent years. In this paper, a high-damping composite driveshaft is designed by combining viscoelastic high-damping rubber material and CFRP material. The damping loss factor of the designed high-damping composite driveshaft, CFRP shaft, and metal shaft is studied by numerical analysis based on the modal strain energy method. In the marine driveshaft system, various types of vibration are prone to occur, and this paper also builds a marine driveshaft system transverse vibration test platform to compare the damping effect of each group of driveshafts on transverse vibration under different working conditions. At the same time, the difference in response to longitudinal excitation of each group of driveshafts is also investigated by static longitudinal vibration test. This study provides a reference for the design and development of high-damping performance composite driveshafts.

Axial compression performance of BFRP strip-PVC tube composite reinforced fiber recycled concrete short columns

XU Dongmei, LIU Huaxin, LI Yan

2024, 0(6): 95-105. DOI: 10.19936/j.cnki.2096-8000.20240628.012

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To investigate the axial compressive performance of short columns of BFRP strip-PVC tube composite reinforced fiber recycled concrete. Axial compression tests and theoretical analysis were conducted on 13 groups of short columns of recycled concrete. The main variables studied were the number of BFRP strip layers (0, 1 and 3 layers), BFRP spacing (25 mm, 37.5 mm and 50 mm), and reinforcement methods (no lateral restraint, BFRP strip reinforcement, and BFRP strip-PVC tube composite reinforcement). The results show that the BFRP strip-PVC tube composite reinforcement can not only improve the ultimate bearing capacity of the specimens, but also improve the damage morphology of the short columns of fiber-reinforced concrete. In the nonlinear strengthening phase of the stress-strain curve, the influence of the reinforcement method on the stiffness of the specimen is more significant. With the increase of BFRP wrapping, the peak stress and ultimate strain of the specimens were significantly increased. The stress-strain calculation model of the softened section established based on the test data has better applicability.

Experimental study on drilling force and drilling quality of GFRP/Al stacks materials

LIU Liping, LIU Bin, LI Qing, PENG Zhiguang, ZHU Xueming

2024, 0(6): 106-111. DOI: 10.19936/j.cnki.2096-8000.20240628.013

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The stacks structure composed of composite materials and metals has been widely used in the aerospace field, but drilling high-quality holes on composite/metal stacks structures remains a challenge. This article aims to investigate the influence of drilling process parameters on the axial force and surface quality of GFRP/Al stacks materials during drilling. The common carbide fried dough twists drill is used to drill the GFRP/Al stacks material “once”, and the drilling axial force is measured by the Kistler dynamometer. The results show that the maximum drilling axial force increases almost linearly with the increase of feed rate per revolution, and decreases slightly with the increase of spindle speed. The drilling process parameters affect the surface quality of aluminum alloy and GFRP hole making. High feed rate per revolution will reduce the burrs at the aluminum alloy hole making outlet, but it will increase the damage at the GFRP hole making outlet; high spindle speed will increase the burrs at the aluminum alloy hole outlet and damage at the GFRP hole outlet. Compared to the feed rate per revolution, the spindle speed has a greater impact on the quality of aluminum alloy and GFRP drilling.

Preparation and properties of glass fiber epoxy film former for thermoplastic composites

PAN Chaochao, LI Peng, PAN Chuncheng, HOU Yong, ZHANG Zhaobin, LU Zedong

2024, 0(6): 112-117. DOI: 10.19936/j.cnki.2096-8000.20240628.014

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In this paper, a waterborne epoxy resin emulsion was prepared as a glass fiber film former by chemical modification method using epichlorohydrin, copolymer P105, epoxy resin E-51 and bisphenol A as raw materials. The effects of molar ratio of raw materials, E-P105 content and emulsification temperature on the particle size and stability of the emulsion were investigated. The results showed that when the molar ratio of P105, ECH, NaOH was 1∶1.5∶1.2, the molar ratio of epoxy resin and bisphenol A was 2.25∶1, the mass of E-P105 was 20% of the total mass of epoxy resin and bisphenol A, and the emulsification temperature was 60 ℃, the particle size of the emulsion was 0.387 μm with uniform particle size distribution and good stability, sized glass fiber composites have excellent mechanical properties.

Comparison of cellular gradient impregnation with hole incidence and radial incidence

ZHANG Yafa, LIU Wenyan, LIU Chenxu, ZHAO Zhibin

2024, 0(6): 118-122. DOI: 10.19936/j.cnki.2096-8000.20240628.015

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The absorbing performance of 2~18 GHz electromagnetic wave aperture incidence and radial incidence carbon black segmented gradient impregnated honeycomb was tested by bowing method. With the increase in the number of impregnation honeycomb structure, there is an optimal immersion number of impedance matching, and the absorption performance is better than that of radial incidence honeycomb structures. Radial incidence gradient impregnated honeycomb, due to the anisotropy of the honeycomb structure, the performance difference between the two directions is large, the honeycomb structure can increase the number of reflections of electromagnetic waves in the honeycomb cavity, with the increase in the number of impregnation honeycomb structure wave absorption performance first weakened and then improved. At the same time, the honeycomb height has a great impact on the honeycomb performance, increase the hole to the incidence of the last section of the impregnated honeycomb height, the overall honeycomb height increases, the overall wave absorption performance of the honeycomb improved, impedance matching effect becomes better, at this time to increase the number of steps of each section impregnated, there is the optimal number of impregnation, impedance matching effect is the best, the best wave absorption performance. Honeycomb structure is widely used in military electromagnetic stealth, gradient impregnation can effectively improve the impedance matching effect, radial gradient impregnation honeycomb to cope with electromagnetic wave large angle incidence has great development prospects.

Application status and development trend of pultruded plates for wind turbine blades

XU Qiang, ZHANG Xiyue, HUANG Huixiu, WANG Zhiwei, LIU Chuanrui

2024, 0(6): 123-128. DOI: 10.19936/j.cnki.2096-8000.20240628.016

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The research and development of pultruded plates for wind power blades at home and abroad are introduced in this paper. Five types of pultruded plates of different material systems are involved, which are carbon fiber pultruded plates, glass fiber pultruded plates, carbon fiber-glass fiber hybrid pultruded plates, pultruded plates without peel ply and polyurethane pultruded plates. The application advantages and challenges of pultruded plates compared with traditional vacuum filling and prepreg composites are analyzed. Combined with the current application status, the future focus direction and development trend of pultruded plates of various material systems are put forward respectively: Glass fiber pultruded plates will still occupy the mainstream in the future onshore wind power blades because of its low cost advantages, and will develop in the direction of higher modulus and lower cost; with the development of offshore wind power and the acceleration of the process of carbon wire localization, carbon fiber pultruded plates will have a broader application prospect; carbon fiber-glass fiber hybrid pultruded plates, pultruded plates without peel ply and polyurethane pultruded plates have obvious advantages in weight reduction or cost reduction, but further research and application experiences need to be carried out.

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