COMPOSITES SCIENCE AND ENGINEERING

Study on biaxial full-stress tensile nonlinear behavior and mechanical parameters of PVDF membrane material

ZHANG Yicong, CHEN Jianwen

2024, 0(4): 5-13. DOI: 10.19936/j.cnki.2096-8000.20240428.001

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To define the biaxial tensile properties of fabric membrane material within the full-stress range,the biaxial monotonic tensile experiments of typical PVDF coated fabric were conducted by setting seven loading ratios. A developed MATLAB program was used to achieve complex deformation properties and accurate elastic parameters of the coated fabric. By this program, the response surface analysis of deformation and mechanical parameters were carried out to reveal the variation and evolution in elasticity modulus, Poisson’s ratio, and orthotropy of the coated fabric under different stress levels and ratios. The results show that elastic parameters and orthotropic characteristics of the material vary noteworthily with stress ratios and levels within the full-stress range. In addition, coupled stiffness coefficient was introduced to represent the proportion of elongation and shrinkage in biaxial monotonic tensile test. The formula of elasticity modulus was derived based on the uniaxial and biaxial tensile stress-strain relation, and the obtained values were in good agreement with the experiment values. The conclusions of investigation could offer beneficial reference for tensile mechanical property of coated fabrics and membrane failure analysis in membrane structure engineering.

Folded graphene microsphere preparation and wettability modulation and its acetone sensing study

WANG Rui, MEI Qilin, DING Guomin, CHEN Shuhui, XU Jianrong, JIANG Duanyang

2024, 0(4): 14-19. DOI: 10.19936/j.cnki.2096-8000.20240428.002

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For the purpose of increasing the surface roughness to obtain superhydrophobic composites, this paper introduced a binary solvent of water-acetone to investigate GO dispersion and evaporation in the binary solvent. Later on, by spray frying method, FGO were obtained to investigate the effect of solvent components on the wettability. Finally, FGO was compounded with PDMS to make an acetone-sensitive superhydrophobic sensor. The results show that GO is well dispersed and has a good evaporation rate in a binary solvent with a 20% water fraction, and the obtained FGO has a contact angle of 149.1°. The prepared composites have good bonding and superhydrophobicity of 150.2°, as well as good sensing performance at acetone concentrations of 0.03~0.075 mol/L, with a sensitivity of 115 (mol/L)^-1.

Study on specific heat capacity and thermal conductivity of glass fiber/epoxy resin prepreg during the whole curing process

MA Shiheng, GE Jingran, LIU Kai, LI Yongshan, LIANG Jun

2024, 0(4): 20-25. DOI: 10.19936/j.cnki.2096-8000.20240428.003

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The specific heat capacity and thermal conductivity of glass fiber/epoxy resin prepreg in different directions during the curing process were measured by modulated temperature differential scanning calorimetry (MDSC), and a model was established to describe the changes of specific heat capacity and thermal conductivity with temperature and curing degree. The specific heat capacity and thermal conductivity of the prepreg increase linearly with the increase of temperature when it is not cured and fully cured. During the curing process, it is subject to the dual effects of temperature and curing degree. In the early stage of curing reaction, there is a sudden change in the specific heat capacity and thermal conductivity, which first increases and then decreases under the effect of temperature and curing degree. In addition, the relationship between specific heat capacity and thermal conductivity with temperature and curing degree is described by mixing law and piecewise linear relationship, which is helpful to improve the accuracy of parameters in numerical simulation.

Improving interlaminar fracture toughness of carbon fiber/epoxy resin composite toughened by BN particles modified PVDF electrospinning fibrous interleaf

ZENG Tangyu, MA Chuanguo, XIANG Yang, SHAO Shilei

2024, 0(4): 26-32. DOI: 10.19936/j.cnki.2096-8000.20240428.004

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To address the problem of delamination damage in fiber reinforced composite laminate, an interleaving method of boron nitride (BN) particle-modified electrospun polyvinylidene fluoride (PVDF) fibrous was proposed to improve the interlaminar fracture toughness of carbon fiber/epoxy (CF/EP) composite laminate. The BN was first uniformly dispersedin PVDF solution by ultrasonic treatment, then BN-modified PVDF fibrous (BN&PVDF) was prepared using an electrospinning method and introduced into the interlayer of carbon fibres as an intercalation material, and BN&PVDF reinforced CF/EP composite laminates (BN&PVDF-CF/EP) were prepared by manual lay-up method and vacuum hot-pressing process. The study focused on the effect of BN particle content in modified PVDF electrospun fibrous on the reinforcement of CF/EP interlaminar fracture toughness and the relevant interlaminar toughening mechanism. The results show that the modified PVDF electrospun fibrous with a BN content of 3.2wt% have achieved the best toughening effect. The mode Ⅰ and Ⅱ interlaminar fracture toughness of BN&PVDF-CF/EP are increased by 129.6% and 160.6%, respectively, compared to that of CF/EP. The introduction of the BN particles increases the tensile strength and modulus of the PVDF fibers. The BN particles areembedded in the PVDF fibers and increase the roughness of the PVDF surface, which enhances the interfacial interaction between the PVDF fibers and the matrix, inducing a more complex toughening behavior and improving the toughening effect of the PVDF fibers.

Prediction of elastic constants of particle-reinforced composite materials based on the improved Halpin-Tsai model

WU Shunxin, ZHU Shuiwen

2024, 0(4): 33-39. DOI: 10.19936/j.cnki.2096-8000.20240428.005

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In order to predict the elastic constants of particle-reinforced composites with different shapes, a representative volume element (RVE) model of different particle shapes was developed to investigate the effects of different particle shapes and their volume fractions on the elastic constants of the composites, taking silicon carbide (SiC) particle-reinforced epoxy resin as an example. And the relationship equations between shape factor and volume fraction, particle volume and geometry factor were derived by the improved Halpin-Tsai model. The results of the elastic constants of composites calculated by the finite element model and the improved Halpin-Tsai model are similar with a maximum error of only 4%. It is shown that the improved Halpin-Tsai model can be used to predict the elastic constants of silicon carbide particle reinforced epoxy composites.

Effect of pore-column taper on the compression properties of fibre-column reinforced sandwich structures

LI Hongjun, HAN Yang, SONG Xiaofei, ZHENG Shaowen, ZHENG Chaofan, SUN Jiuxiao

2024, 0(4): 40-48. DOI: 10.19936/j.cnki.2096-8000.20240428.006

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In order to study the influence of the taper of the pore column on the compression performance of the core structure, 15 sets of fibre column reinforced composites with different tapered pore columns were designed and prepared. Quasi-static compression experiments and numerical simulations were carried out on the prepared sandwich structures to investigate the effects of hole-column taper and core thickness on the compressive strength, modulus, specific strength and failure mode of the sandwich structures. The results show that for sandwich structures with core thicknesses of 25 mm, 30 mm and 35 mm, the increase in hole-column taper from 0° to 16° increases the compression strength by 14.7%, 22% and 24.8%, the compression modulus by 25.9%, 31.6% and 37.7%, respectively, and the specific strength by 4%, 9.95% and 10.24%. Failure of core structures with small and non-tapered pore columns is in the form of buckling and fracture of the fibre column, with the location of buckling and fracture gradually shifting towards the smaller end of the pore diameter as the taper of the column increases. When the taper of the hole column is raised to 16°, part of the core structure with the smaller aperture end of the fibre column becomes debonded from the panel, resulting in the fibre column failing to provide good support and affecting the mechanical properties of the material.

Study on the placement process of CF/PEEK composite laminates based on laser heating

LIU Guansan, SUN Shiyong, MA Xin, HAN Xiaochan

2024, 0(4): 49-55. DOI: 10.19936/j.cnki.2096-8000.20240428.007

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For high quality manufacturing of thermoplastic composites, the CF/PEEK placement platform based on fiber laser heating was designed and built. And the composite laminates were prepared. Then based on the equipment parameters of the placement platform (laser power, placement speed, placement pressure), the experimental analysis of univariate parameters and multivariate orthogonal parameters were performed. Meanwhile, the interlaminar shear strength (ILSS) was measured and the micromorphology was observed. The influence of process parameters of temperature and pressure on the mechanical properties of CF/PEEK laminate was investigated. The experimental results show that ILSS first increases and then decreases with increasing temperature and pressure within the experimental range. The influences of two process parameters(temperature and pressure) on the ILSS of laminates are different and the effect of the placement temperature is greater than the placement pressure during the manufacturing process. The optimal process parameters for preparation of CF/PEEK laminatesin the experiment are placement pressure of 0.2 MPa, placement temperature of 402.6 ℃.

Design and analysis of the back-thrust drone fuselage with balsa core and carbon fiber sandwich composite structure

LIU Feng, QIAO Yu, LI Xuejiang, DOU Guangzheng

2024, 0(4): 56-62. DOI: 10.19936/j.cnki.2096-8000.20240428.008

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A back-thrust drone fuselage with balsa core and carbon fiber sandwich composite structure is designed. The aerodynamic shape design, flow field analysis and internal structure design of the fuselage are completed. The finite element model of the fuselage structure is established and the structure stiffness is checked. The 3D Hashin failure criterion is embedded in the analysis model by subroutine programming. The ultimate state function g(x) is constructed based on the three failure modes, and the strength and stability of the fuselage structure are checked. The initial damage location and mode of the structure are predicted by overload with constant step. The fuselage skin ply optimization is carried out, and the fuselage structure performance with different skin ply is assessed using g(x) function. It is showed that the maximum aerodynamic pressure of fuselage skin for landing and maximum speed flight occurs at the nose fairing area. The values of the ultimate state function g(x) of the two load cases are greater than 0, and the maximum displacement is 3.076 mm and 2.92 mm respectively. The fuselage structure stiffness, strength and stability are verified. With the loading of 1.17 times of the design load to the landing case, the initial compression delamination damage of the balsa core occurs on the lower panel of the fuel tank compartment. The local buckling is found on the fuselage side skin, and the stability of the skin can be improved with the proportion increase of the 45° ply. The structure stability margin is increased by 7.2% due to glass fiber skin ply optimization without weight change.

Research of the low-velocity impact performance of stitch-reinforced PRSEUS components

TIAN Xiao, WEN Liwei, DENG Zhuhai

2024, 0(4): 63-75. DOI: 10.19936/j.cnki.2096-8000.20240428.009

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As a typical structural unit for wing-fuselage fusion layout, the PRSEUS structure is subjected to complex loading conditions. The use of stitching technology to integrate the reinforced structure with the skin can improve the load transfer capability of the fuselage, improve the overall consistency of the PRSEUS structure, and give full play to the loading efficiency of the PRSEUS structure. By preparing stitched PRSEUS components under existing conditions and carrying out experimental studies of low velocity impact, it was found that the increase of either stitch density or stitch fineness can improve the impact resistance of the specimens, and the impact resistance improvement brought by the increase in stitch fineness was relatively small compared to the increase in stitch density. The impact resistance performance of PRSEUS structure is more sensitive to the stitching density. The results of finite element analysis showed that the interlayer properties of the stitched specimens were significantly improved and the damage area was reduced, which proved that stitching can effectively improve the impact resistance of PRSEUS structures.

Finite element analysis of flexural performance of RC beams strengthened with externally bonded CFRP under hygrothermal environment

ZHANG Zhimei, MA Jiachen

2024, 0(4): 76-82. DOI: 10.19936/j.cnki.2096-8000.20240428.010

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To study the flexural performance of externally bonded CFRP-reinforced RC beams under hygrothermal environment, this paper firstly establishes an interface bond-slip model under hygrothermal environment based on the existing two-parameter bond-slip model of FRP-concrete interface and introduces the influence coefficients of humidity and temperature on fracture energy and interface stiffness. Then, the interface model is used to perform finite element numerical simulations on a set of test beams under the action of hygrothermal conditions, and the simulation results are compared with the test results to verify the correctness of the model. Finally, the validated finite element model was used to analyze in depth the effects of factors such as the width ratio of CFRP to concrete and the amount of CFRP reinforcement on the flexural performance of reinforced concrete reinforced beams under different hygrothermal conditions. The results show that the CFRP-concrete bond-slip model established in this paper can effectively simulate the interface performance under the hygrothermal environment; peeling damage mainly occurs in the reinforced beams under the hygrothermal condition, and the flexural load capacity and corresponding deflection of the reinforced beams decrease significantly with the deterioration of the hygrothermal environment; the flexural load capacity of the reinforced beams can be improved by appropriately increasing the width ratio of CFRP to concrete and the amount of CFRP reinforcement under the hygrothermal environment. The flexural load capacity of the reinforced beam can be improved by increasing the width ratio of CFRP to concrete and the amount of CFRP reinforcement.

Ply structure design and molding process of hybrid fiber composite propeller

LIANG Guilong, CONG Qing, LI Xu, WANG Jihui

2024, 0(4): 83-89. DOI: 10.19936/j.cnki.2096-8000.20240428.011

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In order to promote the integrated research on the design and molding process of composite propeller products and emphasize the role of fiber hybrid in the development of high damping and high performance blades, the small-size composite propeller was taken as an investigation object. Based on its surface and geometric characteristics, the material and ply design of the hybrid fiber composite blade were carried out, which results in two propeller ply schemes under the hybrid modes of carbon fiber (CF) and kevlar fiber (KF) respectively. By employing the ACP module in ANSYS Workbench platform, the finite element modelling of anisotropic composite material was conducted, which can be consistent with the actual structural characteristics of the blade. According to the guidance of simulation analysis, the hybrid fiber composite propeller sample model was fabricated by using the molding process of prepreg. Through the static loading test and modal measurement test upon the manufactured propeller blade, the comparisons between experimental and calculation data of its static stiffness and modal frequencies from the 1st to 3rd stage are obtained. The good agreement not only verifies the reliability of the modeling method of composite propeller based on ANSYS ACP, but also verifies the feasibility of manufacturing hybrid fiber composite blade samples by molding process.

Test and design of bending performance of small-angle winding composite revetment pipe piles

ZHANG Heng, FANG Hai, WANG Xiaochun, XIA Guolong, XU Shuang

2024, 0(4): 90-96. DOI: 10.19936/j.cnki.2096-8000.20240428.012

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This paper proposes a new composite revetment pipe pile. The revetment pipe pile is made of composite winding pipe prepared by the fiber winding process. Through the four-point bending test, the failure mode and load-displacement relationship of the specimen were obtained, and the influence of winding angle ±55°, ±15° and whether concrete was poured on the bending performance of the revetment pipe pile was analyzed. The results show that the reduction of the fiber winding angle from 55° to 15° and the pouring of concrete can greatly improve the stiffness and bending bearing capacity of the composite revetment pipe pile. Then, the calculation formula of the embedded end depth of composite revetment pipe piles is derived on this basis, and the design process and application suggestions of revetment pipe piles are given. This provides a reference for the later application of composite revetment pipe piles in revetment projects.

Study of moisture absorption and aging behavior of composite interference riveted structures

GUI Linjing, ZHANG Shiguang, LI Hao, WANG Ankang, LIANG Xinhe, XIA Yanfeng, LIU Jia

2024, 0(4): 97-104. DOI: 10.19936/j.cnki.2096-8000.20240428.013

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The properties of carbon fibers and matrix in carbon fiber reinforced polymers (CFRP) are different, and the resin matrix is sensitive to humidity, so the mechanical properties of riveted composite structures in service in a humid environment differ greatly from those in the laboratory environment. The hygroscopic aging test was designed and the experimental data were fitted using the Zhan’s model to obtain the variation of mechanical properties of CFRP under hygroscopic aging condition, the failure mechanism of the aged material was also studied. Based on this prediction model, a finite element simulation model of composite riveted structure with moisture absorption and aging under different assembly conditions was established, the accuracy of the model was verified by experiments. The effects of moisture absorption aging and assembly method on the bearing performance and failure mechanism of composite and the whole joint structure were investigated by a combination of finite element simulation and experiments.

Optimization of heat insulation winding path based on ant colony algorithm

WANG Haodong, HOU Zengxuan, ZHANG Weichao, LUO Yangyang, LI Yanliang, QI Houliang

2024, 0(4): 105-110. DOI: 10.19936/j.cnki.2096-8000.20240428.014

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To solve the problems of tape tearing, wrinkling and gap control in the winding process of heat insulation, this paper proposes an optimization method of winding path based on multi-factor improved ant colony algorithm. The optimization strategy includes: Constructing the ant decision space, changing the heuristic function, and introducing gap scaling coefficients. Then, using the ACIS geometric modeling library to build the mandrel and tape three-dimensional models, a tape strain calculation method is proposed to evaluate the degree of tape tearing and wrinkling. The winding simulation and experimental verification results show that this method can effectively optimize the winding path of heat insulation, solve the problem of tape tearing and wrinkling, and meet the requirements of winding tape gap, thus improving the quality of heat insulation winding forming. It provides a new path optimization method for heat insulation winding forming process.

Factor analysis of tool wear and its influence on CFRP drilling quality

ZHOU Xinkang, WEI Haojie, CHEN Xiaolong, WANG Jiaxin, LU Dawei, XIE Hui

2024, 0(4): 111-116. DOI: 10.19936/j.cnki.2096-8000.20240428.015

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In order to ensure the processing quality of carbon fiber reinforced resin matrix composites (CFRP), the effect of tool wear on the hole quality of CFRP is studied. By making CFRP laminates, the relationship between tool wear law and hole quality of CFRP materials is quantitatively studied. The tool wear curve is drawn by tracking the wear amount VB of the rear cutter face in the process of marking the customized hole with a digital microscope, and the wear law of the rear cutter face under different rotating speeds is quantitatively compared and analyzed. At the same time, the length and stratification of outlet burr are calibrated by experiments. The quality of the drilled hole is evaluated by the exit burr defect factor and the hole processing delamination defect factor respectively. The correlation curve of defect factor and VB was drawn. Quantitative analysis was made on tool wear factors and their impact on drilling quality. The experimental results show that the cutting tool enters the high-speed wear stage quickly at high speed. In the high-speed wear stage, the tool wear is faster at low speed. After the tool enters the stage of high-speed wear, tool wear gradually becomes the main cause of outlet defects, and the quality of hole making is higher at high speed when the tool wear amount is the same.

Research progress on multi-stimulus responsive strong composite soft actuators

SHENG Jie, LIU Hang, WANG Wenle, JIANG Shengkun, LI Mingxia, HUANG Zhengqiang, GENG Tie, JIANG Lin

2024, 0(4): 117-128. DOI: 10.19936/j.cnki.2096-8000.20240428.016

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Multi-stimulus responsive strong composite soft actuators combine the features of flexibility, adaptability, and structural designability, which can respond to external stimuli and change their structure, shape, and macroscopic properties, leading to an extensive prospect. This review concludes the research progress on multi-stimulus responsive strong composite soft actuators in recent years, introduces the forming and preparation methods of such actuators, and analyses the actuation principle of the actuators. From the perspective of the dimension of reinforced fillers, the effects of various fillers on the actuator response speed, multi-stimulus response, and mechanical properties capability are reviewed. Furthermore, the summary also includes the current application status of this actuator within the fields including soft robotics, micromedical devices, precision sensors, and folded electronics. Finally, the development prospects of multi-stimulus responsive strong composite soft actuators are prospected, which are expected to provide reference and inspiration for the design and preparation of actuators with novel functions and more challenging challenges.

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