COMPOSITES SCIENCE AND ENGINEERING

Out-of-plane tensile failure mechanism of carbon fiber/epoxy composite-metal connection structure

YU Zhangjie, ZHANG Qi, CAI Dengan, DAI Zhengzheng, ZHOU Guangming

2023, 0(7): 5-12. DOI: 10.19936/j.cnki.2096-8000.20230728.001

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A combination of experiment and numerical simulation was used to study the out-of-plane tensile failure mechanism of the composite-metal connection structure, and the influence of different sizes of aluminum alloy lower block on the bearing capacity and failure mechanism was explored. The study found that increasing the contact area between the aluminum alloy lower block and the composite laminate can improve the bearing capacity. Aluminum alloy lower block without chamfering can significantly shear the laminate, causing the laminate to delaminate and leading to premature failure. The addition of chamfers to the aluminum alloy lower block avoids delamination of the laminate and increases the bearing capacity. Based on the constitutive equation, modified three-dimensional Hashin criterion and stiffness degradation method, a progressive damage model of the composite-metal connection structure was established. The predicted failure load and failure mode of the structure are obtained, which are consistent with the test results.

Preparation and performance of graphene/modified polyetheretherketone

LIU Huizhi, MEI Qilin, DING Guomin, XIAO Han, CHEN Shuhui, HUANG Zhixiong

2023, 0(7): 13-18. DOI: 10.19936/j.cnki.2096-8000.20230728.002

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Due to the strong van der Waals forces between the Gr sheet layers and the high melt viscosity of PEEK, the poor dispersion of Gr in the PEEK matrix leads to the decrease of performance. In order to improve the dispersion of Gr in PEEK, PEEK-Aa powder was obtained by chemical modification of PEEK through the mixed acid of acetic acid/nitric acid, and then Gr/PEEK-Aa nanocomposites were prepared by solution blending and melt hot pressing methods. The Gr/PEEK-Aa nanocomposites exhibited good electrical conductivity with a maximum conductivity of 3.41×10^-4 S/cm and a percolation threshold as low as 0.55vol%. In addition, Gr/PEEK-Aa nanocomposites exhibited the best comprehensive performance when the Gr content was 1wt%.

Numerical investigation on dynamic response of bio-inspired honeycomb sandwich beams under impact loading

KONG Xiangqing, ZHANG Wenping, ZHANG Huiling, ZHANG Wenjiao, LI Ruonan, FU Ying

2023, 0(7): 19-25. DOI: 10.19936/j.cnki.2096-8000.20230728.003

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In order to explore the impact resistance of the new bio-inspired honeycomb sandwich beam (BHSB) with double core, a 3D finite element numerical model of BHSB under the impact was established via ABAQUS finite element software. And the numerical simulation results are compared with the experimental results to verify the validity of the model. On this basis, the dynamic response of BHSB under impact load is analyzed and compared with traditional honeycomb sandwich beam (HSB). The numerical model is used to further analyze the influence of geometric parameters such as thickness of rubber core (core Ⅰ),material type and wall thickness of honeycomb sandwich (core Ⅱ) on impact load and energy absorption of BHSB. The results show that, unlike the shear failure of HSB sandwich, the failure of BHSB mainly occurs in the upper skin matrix cracking, while the sandwich remains intact. Compared with HSB, the peak force of BHSB is about twice as high and the overall deformation is smaller. With the decrease of the thickness of core Ⅰ, the impact resistance of BHSB is improved to a certain extent. The change of wall thickness of core Ⅱ has a significant effect on the impact load of the structure, but has no obvious effect on the energy absorption. To compare the dynamic response of BHSB with rubber or PMI foam, it can be seen that the impact performance of BHSB with rubber core is better than that with PMI foam core from the perspective of impact load resistance, but the latter has more advantages in terms of energy absorption effect.

Effects of interfacial van der Waals interaction on the elastic properties of graphene/polyethylene composites

HUANG Lixin, ZHANG Yuanxiu, HUANG Jun

2023, 0(7): 26-34. DOI: 10.19936/j.cnki.2096-8000.20230728.004

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In this paper, the elastic properties of graphene/polyethylene composites were studied by using representative volume element (RVE) combined with micromechanics and finite element (FE) method, and the influences of interfacial van der Waals (vdW) interaction on the elastic properties of graphene composites were analyzed. In the FE model, the carbon-carbon bonds are simulated by the spring elements for graphene, the solid elements for matrix, and the spring elements with the stiffnesses equate to the second derivative of Lennard-Jones potential for interfacial vdW. The vdW number is determined by a simple mathematical model, which makes up for the defect of ignoring the vdW number in existing studies. Sandwich RVE model and embedded RVE model are used to discuss the effect of interfacial vdW on the Young’s modulus and Poisson ratios of graphene/polyethylene composites with different graphene sizes and volume contents. The results show that the interfacial vdW interaction has great effect on Young’s modulus of graphene/polyethylene composites, especially on the Young’s modulus along the direction of graphene thickness, while small effect on Poisson ratios.

Analysis of the propagation coupling law of laser-induced shock wave in the rubber layer

XIONG Chun, REN Ziang, YAN Xiaoyan, LIU Jiayi, XU Jinjun

2023, 0(7): 35-43. DOI: 10.19936/j.cnki.2096-8000.20230728.005

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The study of the propagation and coupling law of laser-induced shock wave in laminated materials is the basis of the realization of this technology. In this paper, a high energy laser-induced plasma shock wave impact bonded specimen was designed, and a numerical model of the laser impact test specimen was established. The coupling process of stress wave propagation in the adhesive layer was simulated, and the particle velocity on the back obtained by the test and simulation was compared to verify the finite element model. On this basis, the simulation method is used to explore the stress wave propagation coupling law in the bond layer when the laser impact bonded specimen with different energy, pulse width and spot diameter. The results show that the laser energy and pulse width both affect the stress wave propagation in the rubber layer. With the increase of laser energy, the peak free particle velocity on the back of the specimen and maximum tensile stress value increase, and the maximum tensile stress depth remains unchanged. With the increase of laser pulse width, the peak free particle velocity on the back of the specimen increases, the maximum tensile stress value increases, and the maximum tensile stress depth decreases.

Research on cold plasma modified PLA fiber/TPS composites

CHEN Yingxuan, MA Huihuang, SUN Ming, YANG Shaoxia, CHEN Jianpei, ZHOU Xiaodong

2023, 0(7): 44-49. DOI: 10.19936/j.cnki.2096-8000.20230728.006

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To improve the mechanical properties of composites by improving the interfacial compatibility between polylactic acid fibers (PLAF) and thermoplastic starch (TPS), the PLAF was modified by cold plasma. And the TPS was prepared by torque rheometer, and PLAF/TPS composite was prepared by compression molding. The effects of different power cold plasma, different fiber lengths, and different fiber contents on the mechanical properties of composites were explored. The results showed that the higher the power of the cold plasma modification treatment, the higher the tensile strength and flexural strength of the composites prepared by the modified PLA fibers, but had little effect on the impact properties of the composites. When the fiber length was 10 mm, the fiber content was at 20%, the comprehensive mechanical properties of the fiber are relatively good: the tensile strength was 16.15 MPa, the bending strength was 56.12 MPa, and the impact strength was 5.54 kJ/m².

Design and verification of composite wing based on composite beam structure

WANG Jing, LU Chang, WU Panpan, LI Chuang

2023, 0(7): 50-56. DOI: 10.19936/j.cnki.2096-8000.20230728.007

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Taking the composite wing with a given shape and size as the research object, the structure design of the wing and the overall forming scheme are studied. The 3D model of the wing is established by CATIA , and the model is set as an isotropic material, and the finite element analysis is carried out with the loading method of three-point bending. Based on the finite element results of COMSOL, the main stress areas of the wing are individually designed. Combining the beam structure buckling and stiffness efficiency criteria, a skeleton scheme of “double C+I-shaped composite beam” is proposed. Then through the displacement response analysis of the central wing box with equal thickness ply, the design scheme of the central wing box ladder ply is proposed. The finite element analysis of the laminated central wing box was carried out by ABAQUS, and the central wing box was further designed by comparing the test results to improve the stiffness of the central wing box. The distribution curing+co-bonding molding process is adopted to avoid filling foam processing and improve the overall load-ratio of the wing. Finally, a composite wing design scheme with high buckling and stiffness efficiency is proposed, in which the total weight of the wing is 316.18 g and the load/weight ratio is 34.85 N/g, which proves the rationality and effectiveness of the design scheme.

Study on the progressive failure of reinforced thermoplastic pipes (RTPs) under axial compression

BU Jiarun, LIU Wencheng, WANG Shuqing, DING Xindong

2023, 0(7): 57-64. DOI: 10.19936/j.cnki.2096-8000.20230728.008

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In the present paper, the numerical model of reinforced thermoplastic pipe based on ABAQUS/Explicit is established, in which the failure mode of composite laminates is determined according to Hashin-Yeh failure criterion, and a VUMAT subroutine based on a nonlinear stiffness degradation model is used to predict the progressive failure process. The progressive failure prediction method could accurately determine the failure mode and position under axial compression conditions. The progressive failure prediction method was verified by a compression experiment, and the relationship between force and displacement obtained by the numerical simulation and the experiment agreed well. Besides,the progressive failure of different failure modes of reinforced thermoplastic pipe under axial compression conditions was analyzed. The results showed that the main failure modes of reinforced thermoplastic pipes are matrix compression failure mode and fiber compression failure mode. The axial elastic stiffness of the pipe decreases with the increase of fiber’s winding angles, and each failure mode appears in different position of pipe. When the fiber’s winding angles is greater than 30°, the dominant failure mode changes from fiber compression failure mode to matrix compression failure mode.

Preparation and research of ultra-thin thermoplastic composite TRAC boom

MA Xinqi, ZONG Wenbo, ZHANG Zhuqing, JIANG Lin, SANG Lin, WU Haihong

2023, 0(7): 65-71. DOI: 10.19936/j.cnki.2096-8000.20230728.009

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Thin-ply prepreg composites show great potential applications in space deployable antenna, solar sail and photovoltaic surface owing to their good elastic strain energy regulation, storage characteristics, and folding deployable structures. This paper introduces ultra-thin carbon fiber reinforced polyamide 6 (CF/PA6) composites and fabricate into TRAC boom using vacuum-assisted hot pressing in an asymmetric ply sequence. Firstly, 1 mm thick one-way laminate was prepared with CF/PA6 composites with a thickness of 0.045 mm and 0.105 mm, respectively, and the flexural performance test and the comparative analysis of the micromorphology after bending failure were carried out. Then, the composite TRAC boom was prepared by asymmetric layup design method and vacuum hot pressing primary molding process. Experimental tests were carried out on the unfolding behavior of the TRAC boom flange and the folding and flexural bearing behavior. The results show that the thickness of the single layer is reduced by 57%, and the bending strength and bending modulus of the laminate are increased by 24.8% and 17%, respectively, which effectively inhibits the interlayer crack propagation of the composite material. The layup structure directly affects the unfolding and closing deformation behavior of the TRAC boom, increasing the proportion of 0° paving, and the specific stiffness and specific strength of the TRAC boom are improved. The experimental results provide a basis for the design and performance evaluation of the deployable structure of thermoplastic composites.

Study on tensile properties of composite glue-screw hybrid connection structure with preload

LI Haiyin, ZHENG Guoyan, WANG Lele, QI Jiaqi, ZHENG Yanping

2023, 0(7): 72-78. DOI: 10.19936/j.cnki.2096-8000.20230728.010

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On the basis of experimental verification of the feasibility of the simulation model, this paper analyzes the influence of pre-tightening force on the bearing capacity of CFRP/titanium alloy bolted connection and hybrid (bonded/bolted) connection structure under the mode of single nail and single lap. The results show that for CFRP/ titanium alloy bolted connection structure, the application of pre-tightening force can effectively increase the failure load of the joint, and the failure load of the joint with 2 N·m tightening torque and 3.5 N·m tightening torque is increased by 11.4% and 13.19% respectively, compared to that with 0.5 N·m tightening torque. For CFRP/ titanium alloy hybrid (bonded/bolted) connection structure, the increase of the failure load by pre-tightening force is weaker than that by bolt connection, but the simulation results of the scalar stiffness degradation (SDEG) of the adhesive layer show that the pre-tightening force can effectively reduce the diffusion of the peeling stress of the adhesive layer and slow down the failure of the adhesive layer.

Study on mechanical properties of continuous glass fiber reinforced thermoplastic composite pipe under pressure

WANG Qi, XIE Yufei, YUAN Lianzhong, GAO Jinke, LU Jiajun

2023, 0(7): 79-85. DOI: 10.19936/j.cnki.2096-8000.20230728.011

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The mechanical properties of continuous glass fiber reinforced thermoplastic composite pipe (RTP pipe) have an extremely important influence on engineering applications. Therefore, the finite element model of RTP pipe under internal pressure was established by using Halpin-Tsai combined model method. Based on the three-dimensional orthogonal anisotropic elastic theory, the maximum stress failure criterion is used to theoretically analyze and calculate the internal pressure burst value of composite pipe. Finally, the short-time burst pressure test of the compound pipe is carried out to verify the analysis. The results show that with the increase of the internal pressure load, the force on the reinforcement layer is much larger than that on the inner and outer layers, and the reinforcement layer plays an important role under the internal pressure. The average bursting pressure of real RTP pipe is 14.15 MPa, the value of finite element simulation analysis is 13.28 MPa, and the relative difference with the experimental results is 6.14%. The theoretical calculated value is 16.34 MPa, which is in good agreement with the experimental value. It has important guiding significance for the design and application of RTP pipeline.

Comparative study on calculation model for compressive strength and ultimate strain of FRP-confined recycled aggregate concrete

XU Senjie, LI Benben, LI Pengju, ZHAN Yang

2023, 0(7): 86-90. DOI: 10.19936/j.cnki.2096-8000.20230728.012

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Experimental database of 318 recycled aggregate concrete (RAC) columns confined by fiber reinforced polymer (FRP) is established in this paper, the applicability of three representative calculation models (Lim’s model, Xiao’s model and Wei’s model) in predicting compressive strength and ultimate strain by the database is investigated. The results show that the prediction accuracy of the three calculation models for compressive strength is higher than that for ultimate strain. Among the three models for predicting compressive strength, Lim’s model shows best accuracy, the average absolute error AAE is only 9.4%, and the average value of the ratio between the predicted value and the experimental value is 100.8%. The predicted value of the compressive strength by Wei’s model is generally lower than the experimental value (Mean=78.9%), and the error is larger (AAE=21.2%) compared with the experimental value. Prediction accuracy of Xiao’s model (AAE=12.8%, Mean=109.8%) is between that of Lim’s model and Wei’s model. When three calculation models predict compressive strength, Lim’s model has the highest accuracy (AAE=21.1%, Mean=95.5%), followed by Wei’s model which underestimates the ultimate strain of RAC confined by FRP (AAE=28.5%, Mean=78.1%). Compared with the experimental value, the predicted value of Xiao’s model for ultimate strain is overall higher (Mean=125.9%), and the error is relatively large (AAE=40.1%). In general, Lim’s model has the best accuracy among the three calculation models in predicting both compressive strength and ultimate strain, and it is recommended to predict the limit state of calculation models in predicting both compressive strength and ultimate strain, and it is recommended to predict the limit state of recycled aggregate concrete confined by FRP.

Design and verification of RTM process for Z-shaped frame of composite fuselage

LIU Juntian, CHEN Jiping, QIU Chunliang, SU Jiazhi

2023, 0(7): 91-97. DOI: 10.19936/j.cnki.2096-8000.20230728.013

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Design and verification of RTM(resin transfer moulding)process for a typical struture of composites fuselage Z-shaped frame parts. The injection scheme of the part is designed and simulated using PAM-RTM, the results show that the resin filling rate can reach 100%. Through the study of the relationship between injection pressure and filling time, it is found that with the increase of injection pressure, the filling time first decreases rapidly and then gradually slows down. Completed the design and manufacture of the RTM tooling, the upper and lower molds can cooperate with different chassis to complete the operation of different processes, and designed the manual hydraulic lifting mechanism to solve the problem of difficult demoulding of RTM process parts. Design of the RTM process flow and complete manufacturing verification, the results show that the part has no significant internal and external defects, thickness deviation within 4%, the volume content of fiber reaches more than 55% and the contour of the part basically meets the requirements. The effectiveness of the Z-shaped frame RTM forming process scheme is verified.

Study on dynamic mechanical properties of carbon fiber reinforced high strength concrete with initial stress damage

HAO Li, ZHANG Kai, WU Wenfei

2023, 0(7): 98-105. DOI: 10.19936/j.cnki.2096-8000.20230728.014

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In order to explore the change law of mechanical properties of carbon fiber reinforced high strength concrete specimens under impact load under initial stress damage, the longitudinal wave velocity and damage factor of carbon fiber reinforced high strength concrete under different stress amplitude (0σ_m, 0.3σ_m, 0.4σ_m, 0.5σ_m, 0.6σ_m, 0.7σ_m, σ_m is the uniaxial compressive strength of the specimen) damage were measured by acoustic detector. Uniaxial impact compression tests of damaged specimens under different strain rates were carried out by electro-hydraulic servo press and split Hopkinson pressure bar (SHPB). The relationships among peak stress, dynamic enhancement factor (DIF), energy dissipation, strain rate and damage degree of specimens are analyzed. The results show that the longitudinal wave velocity of the specimen decreases under cyclic load damage. And the larger the damage stress amplitude is, the larger the longitudinal wave velocity drop of the specimen is, and the increase of the damage factor is increased. There is a quadratic positive correlation between damage factor and stress amplitude. The peak stress decreases by 5.86%, 16.45%, 23.97%, 36.10% and 52.29% respectively under 0.3σ_m, 0.4σ_m, 0.5σ_m, 0.6σ_m, 0.7σ_m damage stress at 0.2 MPa air pressure. The decreasing amplitude keeps increasing, the bearing capacity of the damaged specimen decreases, and the larger the damage stress amplitude is, the higher the damage degree of the specimen is, and the smaller the peak stress and DIF are. Under the action of dynamic load, the incident energy, reflected energy, transmitted energy and dissipated energy of the specimen all increase with the increase of time and finally tend to constant values. With the increase of damage stress amplitude, the reflected energy of the specimen increases, while the transmitted energy and dissipation energy decrease gradually. The effect of stress damage will reduce the energy dissipation density of the specimen, and the larger the damage stress amplitude, the lower the energy absorption effect of the specimen.

Position detection of rubber tape in heat insulation winding molding based on image processing

QIU Chuansen, HOU Zengxuan, YAN Wencong, ZHANG Weichao, LI Yanliang, QI Houliang

2023, 0(7): 106-111. DOI: 10.19936/j.cnki.2096-8000.20230728.015

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In this paper,according to the requirements of automatic rectification control system for winding molding of heat insulation of solid rocket motor, images of rubber tape edge were captured with industrial camera in real-time, and the images were processed based on image processing algorithm to realize the position detection of rubber tape. Firstly, image preprocessing technology was used for image denoising, the double thresholds of Canny algorithm were determined by the maximum inter-class variance method, and rubber tape edge was extracted. Then the rubber tape edge curve was obtained by cubic polynomial fitting according to the extracted edge pixel point set, and the actual position of the rubber tape edge in the winding molding process was obtained. Finally, the deviation of the rubber tape was obtained by comparing the detected actual position of rubber tape with the reference position of rubber tape according to the current winding angle, according to the rectification control algorithms, deviation was converted into the corresponding control variable to control the actuator for rectification. This position detection method is applied to automatic rectification control system in winding molding of heat insulation of solid rocket motor with excellent effect.

Study on winding shape trajectory of carbon fiber reinforced crucible preform

WANG Zheng, DONG Jiuzhi, CHEN Yunjun, JIANG Xiuming

2023, 0(7): 112-119. DOI: 10.19936/j.cnki.2096-8000.20230728.016

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In order to solve the problems of insufficient continuous fiber and circumferential mechanical properties of needled carbon/carbon crucible, a prefabricated carbon/carbon crucible reinforced with carbon fiber was used. Based on the non-geodesic theory, the stable winding equation was established. Based on the tangential point method and the standard line method, the winding linear law of the non-axisymmetric head shell was summarized. The calculation formula of the center rotation angle when the fibers were uniformly filled was derived. The linear design process of carbon fiber winding reinforced by carbon crucible preform was proposed. Under the condition of equal suspension length, the work trajectory equations of four axis winding machine were solved. The effects of tangent points on winding line and winding machine trajectory were studied by simulation. The results of winding tests show that the fiber can be continuously and stably wound, and the fiber can be uniformly covered after a certain cycle. The correctness of the motion trajectory equation of each axis and the feasibility of the linear design method are verified.

Development of experimental platform for reaction injection pultrusion of carbon fiber reinforced nylon 6

ZHOU Jiahui

2023, 0(7): 120-124. DOI: 10.19936/j.cnki.2096-8000.20221228.032

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In this study, an experimental platform for reaction injection pultrusion of carbon fiber reinforced nylon 6 composites was designed and developed. The experimental platform was divided into two modules: the solution preparing system and the pultrusion system. Through the analysis of nylon 6 anionic polymerization reaction conditions and the calculation of feed liquid flow output, the configuration and selection of the solution preparing system and the design of the pultrusion unit heating mold were completed. The development of the experimental platform was completed in combination with the storage and pretreatment system of carbon fiber yarn and the traction system. The carbon fiber reinforced nylon 6 composite plate with complete curing and uniform distribution of resin and 47.48% fiber volume was prepared by running the experimental platform. Taking into account the demand of subsequent continuous industrial production to ensure the continuous supply of feed liquid, a design idea of continuous on-line solution preparing reaction injection machine was proposed, which provides a reference for the preparatory work of industrial production.

Preparation and properties of alumina fiber reinforced boron nitride matrix composites

GAO Longfei, CHAI Xiaoxiao, LI Song, PENG Zhe

2023, 0(7): 125-128. DOI: 10.19936/j.cnki.2096-8000.20230728.018

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The 2.5D alumina fiber reinforced boron nitride (AB) matrix composites were prepared by PIP process with continuous alumina fiber woven 2.5D fabric as reinforcement and boron nitride ceramics as matrix. The mechanical and dielectric properties of AB composites at different sintering temperatures were studied. The fracture morphology and ablation morphology of the composites were analyzed. The results show that AB-1200 composite has excellent mechanical properties, dielectric properties and good ablation resistance. The mechanical properties of AB-1200 composite at 1 000 ℃ are twice that of 2.5D quartz fiber reinforced boron nitride composites under the same conditions. The AB composites can be used as high temperature ablation transparent materials.

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