COMPOSITES SCIENCE AND ENGINEERING

High-temperature high strain rate compression failure mechanism of plain weave CF/PEEK thermoplastic composite materials

YU Xintao, ZHANG Fa, GAO Xin, ZHANG Xu, PAN Zhongxiang, CAO Miao

2025, 0(5): 1-14. DOI: 10.19936/j.cnki.2096-8000.20250528.001

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This paper proposed a method based on multiscale mechanics to predict the impact mechanical response and failure mechanism of plain weave CF/PEEK composite materials under high-temperature and high strain rate conditions. Firstly, finite element models at micro, meso, and macro scales were established based on the real geometric structure and spatial distribution of fibers, fiber bundles, and matrix in the composite materials. A micro-mechanical model was developed based on the typical spatial distribution of fibers within the solidified fiber bundles, and extended to the meso scale to predict the failure modes of fiber bundles under different loading conditions using periodic boundary conditions. Secondly, a meso scale plain weave structure unit cell model was established to obtain the mechanical properties of single-layer plates in the composite materials, and an equivalent connection between microstructure and macro scale performance was established. Finally, temperature field and dynamic compression performance parameters are tested, and a homogeneous model similar to macro specimens is created to verify the effectiveness of the model by comparing with experimental results. Meanwhile, the impact mechanical response and failure modes of the pre-tested specimens were analyzed to reveal the dynamic compression effects of plain weave CF/PEEK thermoplastic composite materials under coupled temperature field conditions. This study provides valuable reference for the safe service of thermoplastic composite materials in extreme environments.

Study on structure and properties of carbon fiber/epoxy composites toughened with short aramid fiber veil interlayers

PENG Yanshuang, XUE Yi, YANG Zehao, ZHAO Qingzhi, ZHANG Wenqiang, FENG Yangyang, LIU Yong, ZHANG Hui, YU Jianyong

2025, 0(5): 15-21. DOI: 10.19936/j.cnki.2096-8000.20250528.002

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For the purpose of enhancing the interlaminar fracture toughness of carbon fiber/epoxy resin (CF/EP) composites, fibrillated short aramid fiber veils (AFV) were prepared by wet netting process in this work and the influence of the areal density of AFV on the interlaminar properties of the CF/EP composites was investigated, with observing the cross-section morphology of CF/EP composites to explore its toughening mechanism. The results demonstrate that the CF/EP composites toughened by 3 g/m² AFV improve the G_ⅠC and G_ⅡC values by 60.6% and 69.7%, respectively, meanwhile, the interlaminar shear properties were improved notably. Combined with SEM analysis, the fibrillation aramid fibers show fiber bridging, fiber pullout, fiber breakage, and longitudinal tearing under stress, thus making the crack path more tortuous and absorbing more energy, the interlayer toughness of CF/EP composites materials is improved.

Numerical study of failure behavior of glass fiber composite material and aluminum alloy double-bolt hybrid joint under tensile loading

YANG Xiao, HE Na, XIAO Peng, ZHU Qiang, CAI Wei, HU Haixiao, CAO Dongfeng

2025, 0(5): 22-30. DOI: 10.19936/j.cnki.2096-8000.20250528.003

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The design of the joint between composite and metal material is a key critical problem in aircraft structural design. It is of great significance to deeply study the mechanical properties and failure modes of composite and metal mechanical connection structures to improve the safety and reliability of aircraft composite and metal hybrid structures. Therefore, this paper established a numerical failure prediction model for the double-bolt hybrid joint of orthogonal braided GFRP laminates and an aluminum alloy plate subjected to tensile loading based on the finite element method. The related finite element simulation analysis and model tests were carried out. The comparison of numerical and experimental results show that the presented numerical model has high accuracy. On this basis, combined with the experimental and numerical results, the differences on failure modes and load bearing capacities between the pure bolted joint and the bonded-bolted hybrid joint under tensile loading were investigated. It is found that the adhesive layer of bonded-bolted hybrid joint can reduce the stress concentration near the bolt hole and improve the stiffness of the whole connection structure. Moreover, the load bearing capacity of bonded-bolted hybrid joint increases by 27.8% compared to pure bolted joint. The research results can provide some useful references for the design of composite-metal connection structure.

Study on mechanical properties of flax/basalt hybrid fiber composites

ZHANG Juanjuan, LI Shijie, CHEN Xianglin, WANG Tao, ZHU Keheng, MU Wenlong

2025, 0(5): 31-37. DOI: 10.19936/j.cnki.2096-8000.20250528.004

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In this paper, flax fiber reinforced polylactic acid composites (FFRP) and flax/basalt hybrid fiber reinforced polylactic acid composites (FBFRP) were made. The tensile and bending tests were carried out to analyze the effects of fiber content and hybrid fiber on the mechanical properties of the composites. Combined with differential scanning calorimetry (DSC) test, the mechanical properties of the composites were analyzed. The results show that for FFRP, when the content of flax fiber exceeds 20%, the tensile properties of the composites increase with the increase of fiber content, and reach the highest value at 40%. A small amount of flax fiber may cause internal defects of the material, and too much fiber content will form agglomeration, which will lead to a decline in the performance of the composite material. For FBFRP, the mechanical properties of the composites are enhanced by adding appropriate content of basalt fiber. When the content of flax and basalt fiber is 30% and 9% respectively, the mechanical properties of the material are the best. Finally, based on the Halpin-Tsai empirical formula and the transversely isotropic numerical simulation including the Tsai-Wu failure criterion, a prediction method for the mechanical properties of hybrid composites is established to accurately evaluate and predict the mechanical properties of hybrid fiber reinforced composites with different fiber contents.

Prediction of cohesive strength of composites based on a bidirectional stochastic micromechanical model

XU Mingchao, TIAN Ali, WANG Qianyi, LUO Yi

2025, 0(5): 38-44. DOI: 10.19936/j.cnki.2096-8000.20250528.005

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To address the complexity of the damage effectiveness mechanism in composites, this paper presents a bidirectional stochastic micromechanical model to characterize the structural cohesive layers using microscopic representative volume units (RVEs) from a micromechanical perspective. This model is used to investigate the cohesive strength of composites under three delamination modes. An extended linear Drucker-Prager yield criterion is selected to parametrically define the stochastic microstructure and predict the initiation of cracks in the matrix. The prediction results demonstrate that the cohesive strength is strongly influenced by the random microstructure morphology, specifically the minimum vertical fiber spacing, minimum transverse fiber spacing, fiber vertical angle, and fiber lay-up angles parameters. By proposing a cohesive strength calculation framework based on the physical mechanism, this study has significant research implications in predicting delamination behavior in composite laminates. Furthermore, it provides an important basis for structural design and performance optimization in engineering applications.

Comparative study of glass transition temperature of epoxy resin tested by different methods

LIU Wei

2025, 0(5): 45-49. DOI: 10.19936/j.cnki.2096-8000.20250528.006

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Glass transition temperature (T_g), as an inherent property of materials, is theoretically independent of the testing method. However, in practice, significant discrepancies often arise between results obtained using different methods and instruments. This study focused on epoxy resins that can be fully cured, using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) to measure T_g respectively. By comparing the results from these two techniques, the research identifies the causes of discrepancies in T_g values, such as differences in testing methods, instrument types, heating rates, and other factors. The study also explores new approaches to improving the consistency, reliability, and comparability of thermal performance (T_g) characterization across different materials.

Effect of ATH/EG on flame retardancy properties in phenolic resin composite

WANG Xin, CAO Jingyi, NI Aiqing, WANG Bing, LI Xiang, YIN Wenchang, WANG Jihui

2025, 0(5): 50-58. DOI: 10.19936/j.cnki.2096-8000.20250528.007

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In this paper, the flame retardant system of aluminum hydroxide (ATH) and expandable graphite (EG) is used as to improve the fire retardancy of carbon fiber reinforced phenolic resin composites (CFPF). The flame retardancy and mechanical properties of the composites with different mass ratios of the two ingredients were investigated experimentally, including the smoke suppression performance, thermal degradation behavior, tensile and bending properties, and residual carbon morphology. The experimental results showed that the addition of the two flame retardants improved the flame retardancy, smoke inhibition performance, and thermal stability of the composites. The limiting oxygen index (LOI) of the flame retardant CFPF-2 sample in which the mass ratio of ATH and EG was 1∶2 is increased by 68.4% compared to the non-modified CFPF-0. The result of cone calorimetry test shows that the peak heat release rate (pHRR), total heat release (THR), total smoke generation (TSP), and average specific extinction area (ASEA) of the CFPF-2 composites are improved by the addition of the two flame retardants. The pHRR, THR, TSP and ASEA of CFPF-2 decrease by 49.73%, 65.30%, 94.89% and 94.63%, respectively, compared to CFPF-0. The result of smoke density test shows that the maximum specific optical density (D_s,max) of CFPF-2 decreases by 93.71%. This indicates that ATH and EG have a very good synergistic effect, especially in smoke suppression. The results of thermogravimetric analysis (TGA) show that the carbon residue of CFPF-2 is increased to 13.72%, a significant improvement compared to the 2.70% of CFPF-0. In addition, the mechanical property test results show that the ATH/EG flame retardant system can improve the tensile and flexural strengths of the CFPF composites.

Effects of molding process and lay-up structure on the defects and mechanical properties of CF/PPESK composites

WANG Yutong, QIAO Yue, JIA Hang, ZHANG Yu, CHEN Xi, LIU Cheng, JIAN Xigao

2025, 0(5): 59-67. DOI: 10.19936/j.cnki.2096-8000.20250528.008

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In this paper, the prepreg of continuous carbon fiber reinforced poly(phthalazinone ether sulfone ketone) resin matrix composites (CF/PPESK) was prepared using the solution impregnation method. Through an orthogonal test, the concentration of the impregnating solution and process parameters for prepreg-making equipment were optimized. When the concentration of impregnating solution is 20wt%, the roller speed is 7 r/min and the strip width is 6.5 mm, the resin volume content and areal density of the prepreg are 40.01% and 218 g/m², respectively. CF/PPESK were prepared by hot pressing, the defects and properties of isotropic (QI) composite laminates under different forming processes were investigated, by the ultrasonic phased array and three-point flexural test. The results show that the defect of QI laminates is the least, the flexural strength and modulus are 345 MPa and 46 GPa, when the molding temperature and pressure are 350 ℃ and 16 MPa, respectively. The flexural strength retention rate of composite laminates with different lay-up structures are 60%~62% at 250 ℃. In order to improve the flexural strength of CF/PPESK@QI composite laminates, by MWCNTs-P is blended with PPESK resin matrix, the flexural strength of laminates with different lay-up structures could be improved by 39%~46%, At 250 ℃, the flexural strength retention rate of composite laminates with different lay-up structures are 47%~52%.

Continuous fiber reference laying path based on least squares polynomial fitting

ZHU Xinyan, SUN Pengwen, SUN Wenbo, ZHANG Lanting, WANG Zirui, LI Hongyu

2025, 0(5): 68-72. DOI: 10.19936/j.cnki.2096-8000.20250528.009

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To further study the fitting method of the reference path for fiber curve laying, and find a more accurate expression of space curve, the reference path fitting method based on least squares polynomials is proposed. By comparing the fitting effects and errors of different type basis functions, the polynomial was determined as the fitting basis function. Based on the Least squares polynomial fitting method, the corresponding Matlab program was written to solve the reference path parameter equation, and continuous fiber curve laying reference paths were obtained. The feasibility and accuracy of the least-squares polynomial fitting were verified by numerical example.

Damping prediction of viscoelastic composite laminates based on macro and micro models

ZHU Suian, ZHANG Hong, LI Xiangping, LIU Bingfei

2025, 0(5): 73-80. DOI: 10.19936/j.cnki.2096-8000.20250528.010

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A finite element method based on macro and micro models was proposed to solve the modal damping of composite laminates. This method takes the modal analysis results of laminated plates as the boundary condition input for a unidirectional fiber RVE model with a viscoelastic matrix. The anisotropic loss factor with frequency and strain dependence is calculated, and the strain energy method is combined to introduce damping that conforms to the actual distribution in the macroscopic model. The modal damping of laminated plates is solved using complex frequency analysis steps in finite element software. Compared with existing damping prediction methods, the calculation results of this method have a trend closer to experimental data, and only the material properties of the microscopic components need to be defined to achieve damping prediction of composite materials with any volume fraction and any layer. It has a wider applicability and provides a reference for using general finite element software to analyze various types of composite.

Gradient design and low-velocity impact response of arched anti-tetrachiral honeycomb sandwich structure

XIANG Shuanglin, ZHOU Xia

2025, 0(5): 81-89. DOI: 10.19936/j.cnki.2096-8000.20250528.011

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Based on the concept of density gradient, three kinds of hybrid metal-fiber/polymer sandwich panel with arched and different density gradients of anti-tetrachiral honeycomb core layers were designed. The numerical model was established and the numerical simulation results were compared with the existing experimental results to verify the effectiveness of the model. On this basis, the effects of impact energies on the peak impact force, impact resistance, energy absorption and damage of different gradient arched sandwich panels were studied. At the same time, the dynamic response of the arched sandwich panel with the negative gradient under repeated impacts was further discussed. The results show that the gradient factor of the core layer has an important effect on the damage and failure modes of the sandwich panels due to the different core layer structures. Under low-energy impact loadings, the peak impact force increases with the increment of the gradient factor. Compared with uniform sandwich panels, gradient sandwich panels also have better energy absorption, and the energy absorbed can reach up to 32.8% than the uniform sandwich panels. At higher impact energies, the gradient factor has no significant effect on peak impact force and energy absorption. Under repeated impacts, the front facesheet and the core play a major role in the total energy absorption of the negative gradient sandwich panel, and the core layer accounts for 66% of the total energy absorption on average. As the number of impacts increases, the deformation and damage modes of the sandwich panel change from local deformation of the upper facesheet to failure,the deformation densification of the core layer to the overall collapse, and the overall lateral bending for the sandwich panel.

Numerical and experimental research on riveting process of carbon fiber composites

LIU Yakang, NI Wenbo, WANG Xuemei

2025, 0(5): 90-95. DOI: 10.19936/j.cnki.2096-8000.20250528.012

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Focus on the research of pulling riveting connections between carbon fiber composite panels, and the riveting process of CR7621 blind rivet commonly used on rail vehicle body was numerically simulated, and using a riveter with riveting process force-displacement detection function for comparative experiment, and the forming situations and mechanical properties of the riveted joints were obtained. Comparative analysis shows that the internal and external forming conditions of numerical simulation are basically consistent with the experimental results, and the deviation of key data such as the diameter of rivet sleeve bulge and the maximum riveting force is within 5%. Further conduct shearing test of the riveted joints on the test machine, the failure form of the joint is that the end of the rivet sleeve is cut off, and the load-displacement curves have good consistency during failure, the average maximum load is 17.7 kN, the average displacement is 5.47 mm. The research can provide support for the application of riveting technology between carbon fiber composite components of rail vehicles.

Textile reinforcement permeability prediction based on improved pore network model

FAN Qi, WANG Jing, YANG Bin, WANG Jihui, NI Aiqing

2025, 0(5): 96-107. DOI: 10.19936/j.cnki.2096-8000.20250528.013

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A method for predicting the in-plane permeability of composite fabric reinforcements through a pore network model was established. First, a three-dimensional image sequence was obtained by non-destructive scanning of the fabric sample using micro-computed tomography (Micro-CT), and the image was binarized, separated into pore areas, and segmented using watershed segmentation to extract the pore network model. The influence of two segmentation methods on the parameters of the pore network model was compared. Secondly, considering the flow inside the pores and modifying the parameters such as the length and radius of the pore network unit, a fictionally-graded micro-tube flow model was adopted to improve the algorithm for calculating the permeability coefficient of the pore network model. Finally, based on the pore network model, the in-plane permeability of three fabrics was predicted. The results showed that the error in predicting the in-plane permeability of 2D fabric pore network model was less than 21.2%, and the improved hydraulic conductance algorithm reduces the prediction error by 27.1%.

Study on basic mechanical properties of GFRP-areca palm stick composite members

YANG Jing, WANG Zhenzhen, ZHANG Haibin, ZHANG Chong, ZHOU Zhi

2025, 0(5): 108-116. DOI: 10.19936/j.cnki.2096-8000.20250528.014

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To enhance the utilization rate of local materials on tropical island and reduce island project construction costs and improve construction efficiency, this paper proposes a low-cost composite members form of GFRP-restrained areca palm stick and studies its basic mechanical properties. Through axial compression and four-point bending tests on 10 GFRP-areca palm stick composite member and 2 control specimens, the effects of different GFRP wrapping directions and layers on the failure mode, axial compression characteristics, and bending properties of the elements were studied. The test results show that the axial compressive bearing capacity of the GFRP-areca palm stick composite member is increased by 110.28% to 925.18% compared to the control specimen, while the bending bearing capacity is increased by 92.20% to 1 063.42%. The single direction wrapping method makes the composite specimen lack fiber constraint in the uncovered direction, causing some composite specimens to have a failure mode similar to the bare pole. Only wrapping the longitudinal and transverse directions along the entire length can provide sufficient constraint for the GFRP-areca palm stick composite member, thereby changing the failure mode of the specimen and improving its mechanical properties. The research results will provide theoretical basis for the promotion and application of GFRP-areca palm stick composite member.

Research on axial compression test and mechanical properties of GFRP-cross-shaped steel-reinforced concrete columns

ZHANG Yunfeng, MA Jinhui, ZHANG Jiarui, TENG Zhenchao, WANG Tong, LIANG Chenguang

2025, 0(5): 117-124. DOI: 10.19936/j.cnki.2096-8000.20250528.015

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The purpose of this paper is to study the mechanical properties of fiber reinforced composite (GFRP) steel reinforced concrete short columns under axial compression. The axial compression tests of 6 GFRP tubular steel-reinforced concrete short columns with different combinations were carried out, and the mechanical model of GFRP tubular cross-shaped steel-reinforced concrete columns was established by ABAQUS for parameter analysis. The effects of different section forms, web spacing, slenderness ratio and fiber winding angle on the axial compressive properties of the member are studied. The test results show that the ultimate bearing capacity of the new steel reinforced concrete column with stiffening ribs is about 6% higher than that of the traditional steel reinforced concrete column. The ultimate bearing capacity of composite columns increases significantly with the increase of the spacing between steel webs. With the increase of slenderness ratio, the ultimate bearing capacity and stiffness of composite column decrease. The ultimate bearing capacity of the member with a single-layer fiber winding angle of 0° is 39% higher than that of the member with a fiber winding angle of 45°, but the initial stiffness of the member has little effect. At the same time, the ultimate bearing capacity and stiffness of alternately arranged fiber winding angle have no obvious change law.

Stability analysis and experimental validation of composite long variable pitch rod compression bar considering initial deflection

SUN Jiameng, ZHANG Fei, DONG Jinshan, LU Yuhui

2025, 0(5): 125-131. DOI: 10.19936/j.cnki.2096-8000.20250528.016

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The mechanical properties of composite long pitch rods are investigated, with special attention to the equivalent stiffness and critical load. Firstly, the equivalent stiffness is calculated by experimental and numerical simulation methods respectively, and the equivalent stiffness results of the two methods have an error of 1.41%. Secondly, based on the three methods of theoretical analysis, numerical simulation and test, the critical load under the existence of initial deflection of the composite long pitch rod is determined. The results show that the error of numerical simulation results relative to the test results is 7.9%, and the error of theoretical calculation results relative to the test results is 14.6%. On this basis, the significant effect of different initial deflections on the critical load is analyzed by numerical simulation, and when the initial deflection is 8.00 mm, the composite long pitch rod buckles at 10.73 kN, which does not meet the use requirements. Finally, the equations for the critical load and initial deflection of the composite long pitch rod are proposed to provide a design basis for manufacturing and maintenance.

Defect detection of pultrusion plate based on improved YOLOv5s

XU Dongliang, LAI Jiuheng, YANG Huilan

2025, 0(5): 132-141. DOI: 10.19936/j.cnki.2096-8000.20250528.017

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In order to solve the problems of low detection precision and slow detection speed in traditional pultrusion plate defect detection methods, a defect data set of glass fiber pultrusion plate was created, and a defect detection model of glass fiber pultrusion plate based on improved YOLOv5s was proposed. The main improvements were as follows: in the feature extraction network part, EvcBlock module was added to enhance the feature extraction ability of small targets, and CBAM attention mechanism was added to improve the attention of important features; the lightweight model was realized by using C3-FASTER module to optimize the C3 module; a new type of loss function ShapeIoU with shape loss was introduced into the detection end, which optimized the fitting effect of the predicted frame and the real frame, and improved the precision of defect detection. The experimental results demonstrate that: in comparison to the original YOLOv5s model, the mAP@0.5 of the improved YOLOv5s model has increased by 3.6%, reaching 88.7%, while the number of parameters has been reduced by 2.1%. The detection speed of the improved model is 121.95 frames per second, and its overall performance is superior to 5 models such as YOLOv8s, which can meet the needs of pultrusion plate defect detection.

Exploration of damage failure analysis of civil aircraft composite components in quality optimization

ZHANG Guishu, CHENG Sheng, WAN Jiajia, SHEN Bingfeng, ZHONG Li, LIU Yanyan

2025, 0(5): 142-148. DOI: 10.19936/j.cnki.2096-8000.20250528.018

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With the production and service of composite components for domestic civil aircraft, the problem of damage and failure of composite components is gradually emerging, which poses challenges to the existing design, molding process, hole making, assembly, inspection, acceptance requirements, and specifications. To further rationalize the control of quality and reduce service damage, a quantitative mechanism for component damage failure analysis and evaluation has been established based on the establishment of a raw data platform for component design, manufacturing, and service, and the study of component damage evolution failure mechanism and fractography. Combined with the quantitative analysis of the damage evaluation of the outer hatch of the landing gear, the feasibility of the mechanism is explored, which provides new ideas for the optimization of batch production quality of composite components and promotes the optimization of component design, process, inspection and acceptance requirements or standards.

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