COMPOSITES SCIENCE AND ENGINEERING

Research on dynamic mechanical properties and model verification of MRE based on composite rubber

MA Qianying, LI Shuai, GAO Xiaomin, WU Zonghuan

2023, 0(9): 5-12. DOI: 10.19936/j.cnki.2096-8000.20230928.001

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In this paper, the dynamic mechanical properties of the developed composite rubber-based magnetorheological elastomer materials were studied, and their mechanical properties were tested by cyclic shear test. Three groups of shear experiments were designed. The effects of strain amplitude, loading frequency and external magnetic field on the mechanical properties of MRE were studied respectively. The hysteresis curves of MRE under different loading conditions were drawn. According to the experimental data, the maximum damping force, equivalent stiffness, storage modulus, dissipation energy, loss modulus and loss factor were calculated. The experimental results show that the energy dissipation capacity of MRE is significantly affected by amplitude and frequency. Within 200% amplitude and 2.0 Hz loading frequency, its energy dissipation capacity is positively correlated with amplitude and frequency range, and its energy dissipation capacity is more affected by amplitude than by frequency. The external magnetic field can also improve the energy dissipation capacity of MRE, but at the magnetic field intensity above 50 mT, the improvement trend of this MRE performance is significantly weakened. Finally, the Bouc-Wen model is used to describe the dynamic mechanical properties of MRE, and the parameters are fitted by the least squares algorithm with Simulink. The analysis of the fitting results shows that the maximum fitting error between the maximum damping force and the dissipation energy is less than 10%, and the average error is less than 5%.

Vibration characteristics of laminates with different repair configurations in hygrothermal environment

ZHAO Yaobin, SHAN Jinyang, CUI Kaixin, LU Xiang

2023, 0(9): 13-20. DOI: 10.19936/j.cnki.2096-8000.20230928.002

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Through theoretical derivation and finite element simulation, the vibration characteristics of step-lap repair laminated plates with different damage depths at different temperatures and moisture contents under free boundary conditions are explored. Based on Voklkersen bonding joint model and considering the influence of damp heat effect, the motion balance equation of the repaired laminate is obtained, and the vibration characteristic equation of the repaired laminate is derived. The finite element model of laminated plates with different patching depth is established in ABAQUS software and verified by experiments. Under the conditions of different temperatures and moisture contents, the effects of the number of patching layers, the number of additional layers and the lap length on the vibration characteristics are analyzed. The results show that the increase of natural frequency of repaired laminates increases with the increase of the number of repaired layers; laminates with additional layers can better maintain the natural frequency, and the effect of two layers of additional patches is better than that of one layer; the natural frequency of laminates with non-penetrating repair configuration increases with the increase of lap length; for the penetration repair configuration, its natural frequency is more easily affected by temperature, moisture content and lap length. In the high-temperature dry environment (T=100 ℃, C=0%), when the lap length changes from 1.5 mm to 9 mm, the penetration repair configuration with a lap length of 4 mm has the lowest natural frequency.

Synergistic modification of CF/PPS composites by phenolphthalein-type polyaryletherketone and silane coupling agent

ZHAO Le, CHEN Zhengguo, YANG Qing, DIAO Chunxia, LU Chengzhi, WANG Shaofei, LIU Yong, ZHANG Hui

2023, 0(9): 21-28. DOI: 10.19936/j.cnki.2096-8000.20230928.003

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In this paper, different concentrations of KH570 solution and 0.5wt% PEK-C solution were used to modify CF in turn, and CF/PPS composites were prepared by compression molding. The CF/PPS composites were characterized by means of X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), X-ray diffractometer (XRD), and universal material testing machine. The results show that after sequentially treating CF with 2wt% KH570 solution and 0.5wt% PEK-C solution, the interfacial properties and bending properties of the composites are significantly improved. Compared with the unmodified CF/PPS composites, its bending strength increased from 709 MPa to 953 MPa, an increase of about 34.4%, and the ILSS increased from 23.8 MPa to 53.3 MPa, an increase of about 123.9%.

Study on interlaminar fracture toughness of self-healing composites based on multi-scale analysis

YANG Weiya, GAO Dongchen, TIE Ying, ZHANG Zhenzhen, GE Chaokun

2023, 0(9): 29-35. DOI: 10.19936/j.cnki.2096-8000.20230928.004

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In order to study the dual toughening effect of the thermoplastic EMAA fiber suture on the interlayer fracture toughness of carbon fiber composite laminates and the toughness after heat repair, experimental and numerical multi-scale modeling methods were used, the type Ⅰ interlaminar fracture toughness of carbon fiber composite laminates with EMAA suture network before and after thermal repair was analyzed. The equivalent mechanical parameters of carbon fiber bundles were predicted by the microscopic model of carbon fiber bundles, by measuring the meso-structure of the monolayer at the suture line, a meso-scale unit cell model was established to predict the equivalent mechanical parameters of the unit cell. The macro model of DCB specimen was constructed, and a viscous layer was added to the macro model to simulate EMAA repair agent to conduct type Ⅰ interlaminar fracture toughness analysis. Three-dimensional Hashin failure criterion and progressive degradation model were used to conduct damage analysis on fiber bundle and matrix, and bilinear constitutive model was used to determine the failure of viscous layer. The effectiveness of the multi-scale model is verified by comparing the experimental results with the simulation results. The simulation and experimental results show that the EMAA suture network can effectively improve the fracture toughness between layers and slow down crack propagation. Moreover, the three-dimensional suture network can send self-healing EMAA into the injury area, and then achieve high recovery of fracture toughness between layered cracks (repair rate of 175%).

Experimental study on low temperature mechanical properties of basalt fiber concrete under impact load

ZHANG Zhipeng, ZHANG Kaizhang, GONG Da

2023, 0(9): 36-41. DOI: 10.19936/j.cnki.2096-8000.20230928.005

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The effects of temperature effect and strain rate effect on the mechanical properties of basalt fiber reinforced concrete were studied based on experiments. An electro-hydraulic servo press and a split Hopkinson pressure bar (SHPB) were used to carry out uniaxial compression tests of basalt fiber reinforced concrete under different impact pressures in low temperature environments (10 ℃、0 ℃、-10 ℃、-20 ℃、-30 ℃). The relationship between specimen stress-strain curve, compressive strength, tensile strength and growth factor with temperature and impact pressure was analyzed. The results show that the decrease of the temperature increases the peak stress of the specimen, while the peak strain decreases. Compared with 10 ℃ under the action of 0.55 MPa impact air pressure, the compressive strength of the specimens increased by 1.50%, 7.09%, 15.83% and 23.34% at the temperatures of 0 ℃, -10 ℃, -20 ℃ and -30 ℃. The strength increases 10.34%, 23.17%, 38.86% and 60.78%, respectively. Under the action of low temperature, the peak compressive strength and tensile strength of the specimen increase, the resistance to external load increases, and the ductility decreases. Under different impact pressures, the compressive and tensile strength DIF of the specimen increases with the decrease of temperature. The low temperature environment makes the specimen more sensitive to the strain rate effect, and the strain rate effect sensitivity of tensile strength is higher than that of compressive strength. In the low temperature environment, the influence of the peak tensile strength and compressive strength of the specimen should be given priority to the temperature effect, followed by the strain rate effect.

Prediction and experimental verification of mechanical properties of composite materials based on failure theories

XIA Wanying, LI Zhihu, QIN Yulin, ZHANG Ning, YAN Luping

2023, 0(9): 42-47. DOI: 10.19936/j.cnki.2096-8000.20230928.006

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Aiming at the research of mechanical strength prediction methods of fiber reinforced composite material, the mechanical properties such as maximum load, maximum displacement, elastic strength, modulus and other mechanical properties were obtained by the method of actual test and simulation analysis through the HyperWorks and ABAQUS with Tsai-Wu tensor theory and Hashin failure criterion. By comparing the simulation results with the test results, it is found that the accuracy of prediction based on Tsai-Wu tensor theory is significantly lower than that based on Hashin, which indicates that Tsai-Wu tensor theory is more suitable for checking the working condition safety performance, and Hashin failure criterion is more suitable for the actual ultimate strength prediction. At the same time, the established simulation model is in good agreement with the experimental results, which indicates that the prediction model has good rationality.

Experimental study on compression configurations and damage failure of 2.5D-C/C composites

MENG Yi, YANG Shengchun, LIU Xiaochuan, YANG Hailong, SONG Guibin

2023, 0(9): 48-54. DOI: 10.19936/j.cnki.2096-8000.20230928.007

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In order to explore the damage process of 2.5D-C/C composites under room temperature compression test, the experimental results and damage modes under different compression configurations were compared by experimental methods. At the same time, the acoustic emission (AE) technology was used to realize online damage monitoring. The improved K-means clustering algorithm was used to carry out pattern recognition of AE signals, combined with the statistical analysis of the changes of AE signals and the microscopic characterization of scanning electron microscopy (SEM), it is found that the damage modes of 2.5D-C/C composites during compression test includes matrix cracking and crack propagation, interfacial debonding and fiber bending fracture. The damage modes is matched with AE signal to describe the evolution process of compression damage of the material.

Preparation and properties study of wave-transmitting and hydrophobic coatings

LI Huaifu, LIU Xumin, WANG Zhi, CHAI Pengjun

2023, 0(9): 55-60. DOI: 10.19936/j.cnki.2096-8000.20230928.008

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As the outermost material of the radome, the wave-transmitting coating not only protects and beautifies the radome, but also realizes the electromagnetic function of wave-transmitting. The hydrophobic coating on the surface of the radome can effectively reduce the adhesion of water droplets on its surface and reduce the influence of water droplets on the wave transmission performance of the radome. In this paper, a hydrophobic surface was constructed by incorporating mesoporous silica particles in a low-dielectric fluorocarbon resin coating. The research results show that the hydrophobic angle of the 10wt% silica particle coating system reaches 129.4°. At the same time, the modification of the mesoporous silica particles by the coupling agent improves the dispersibility of the particles in solution. We comparatively studied the impact resistance, pencil hardness, adhesion, dielectric properties, wave transmission properties of the coating systems. The results show that the coating ratio of modified 10wt% mesoporous silica particles has excellent comprehensive properties and wave-transmitting properties, and realizes the integration of wave-transmission and hydrophobic function of the randome coatings.

Research on first-ply failure prediction of fiberglass reinforced plastic pipes based on PSO-BP neural network

LI Yuanhao, HU Shaowei, SHAN Changxi, MU Zhao, PAN Fuqu, LI Jiang

2023, 0(9): 61-66. DOI: 10.19936/j.cnki.2096-8000.20230928.009

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Predicting the first-ply failure of fiberglass reinforced plastic (FRP) pipe is essential to ensure service safety in water conveyance projects. In this research, a particle swarm algorithm optimized backpropagation neural network (PSO-BP) is used to predict the first-ply failure of FRP pipe under biaxial stress. Experimental data verify the prediction results of the PSO-BP model as well. The results illustrated that the average prediction accuracy of the PSO-BP neural network model for the first-ply failure of the FRP pipe could reach more than 85%, which has advantages over the control backpropagation neural network model regarding convergence and accuracy. The plotted biaxial failure envelopes of axial and hoop stresses showed that the failure envelopes predicted by the PSO-BP model are very close to the failure envelopes measured in the test. The predicted failure envelopes are primarily located in the test failure envelopes. Most of the predicted failure envelope is located inside the test failure one. Therefore, the model is a rational safety prediction model, which can be used as an effective approach to identify FRP pipes before they are qualified according to the specification.

Research on the influence of structural parameters on the joint performance of hybrid bonded-bolted joint for CFRP with three bolts

YANG Xiaodong, SHI Jianwei, CHEN Dong, LI Cheng

2023, 0(9): 67-72. DOI: 10.19936/j.cnki.2096-8000.20230928.010

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The influence mechanism of different structural parameters on the joint performance of carbon fiber reinforced composite (CFRP) hybrid bonded-bolted joint with three bolts was investigated by experiments and numerical simulations. The finite element model based on the three-dimensional Hashin failure criterion was established, and the failure area of the joint was observed with the help of the ultra-depth of field device Keyence VHX-6000. The influence of lap length, bolt hole spacing and clearance fit relationship on the joint connection performance was explored. The results show that increasing the lap length can transfer the stress distribution from the edge of the joint to the middle of the joint, and improve the joint performance by 29.9%. Reducing the spacing of bolt holes can improve the connection performance of the bonding area at both ends of the joint, and the joint performance is increased by 15%. Because of the uneven force of the three bolts, so when the two bolt holes are clearance fit, the force of the middle bolt can be increased, and the joint performance is improved by 6.9%. The joint performance increases with the increase of lap length, but the growth rate gradually decreases to zero. With the increase of bolt hole spacing, the joint strength increases slowly at first and then decreases rapidly, and the optimal bolt hole spacing is 15 mm. When the bolts at both ends are clearance fit, the connection performance of the joint can be increased. The optimal bolt hole diameter is 5.2 mm.

Study on green synthesis of dicyclopentadiene phenol resin for electronics

CAI Shiqi, WANG Songsong, SHI Jian, CHEN Li, LI Weimin, XIONG Yi

2023, 0(9): 73-79. DOI: 10.19936/j.cnki.2096-8000.20230928.011

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In this paper, dicyclopentadiene (DCPD) and phenol were used as raw materials, and a new strong acidic cation exchange resin made by ourselves was used as the catalyst for alkylation reaction. The reaction of phenol with DCPD was catalyzed to produce dicyclopentadiene phenol resin (DPR). Using cation exchange resin to replace the traditional fluorine-containing catalyst as the catalyst of alkylation reaction reduces the production of fluorine-containing wastewater and is more green and environmental friendly. By changing the reaction time, reaction temperature, raw material ratio, catalyst dosage and orthogonal experiment, the optimal process conditions of alkylation reaction and the influence of sulfonation degree of cation exchange resin on the product are explored, so that the synthesized resin can meet the requirements of electronic resin. At the same time, the structure of DPR resin was explored, and the contents of components with different degrees of polymerization in DPR resin, as well as the softening point and yield of DPR resin were determined. The experiment shows that when the new strong acidic cation exchange resin is used as the catalyst, the reaction conditions are 3 h, 120 ℃, the ratio of raw materials is 4∶1, and the amount of catalyst is 20%, the content of component with polymerization degree of 0 can reach 92.36%.

Effect of heat treatment on deformation of CF/PEEK thermoplastic composites

WANG Weize, LIU Rong, YU Hang

2023, 0(9): 80-84. DOI: 10.19936/j.cnki.2096-8000.20230928.012

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Carbon fiber reinforced polyetheretherketone (CF/PEEK) is a thermoplastic composite material with excellent properties. CF/PEEK is sensitive to conditions such as temperature and pressure during the molding process, and different heat treatment conditions can have an impact on the deformation of the part. During the curing of composites with curvature, internal stresses between the laminates are released during demolding, which can cause deformation of the material and affect the accuracy and later use of the molded part. Based on the enhancement of the mechanical properties of CF/PEEK by the heat treatment process, this paper focuses on the effect of the heat treatment process on the deformation of CF/PEEK, designs in-situ film heating equipment for the manufacture of curved parts, uses cylindrical molds to process C-shaped parts, explores the effect of different melting temperatures as well as different annealing temperatures on the deformation of the material, finds the optimal process curve and discusses the factors that may affect the deformation at different annealing temperatures. It was found that the spring-back angle of the parts at different melting temperatures ranged from 0.325 7 to 0.473 7, and the deformation of the parts at an annealing temperature of 250 ℃ was the smallest. This study aims toutilize more efficient manufacturing methods, to improve the quality of the molded parts after curing composite materials and help them to be better used in the aerospace field.

Study on drilling technology and axial force prediction of CFRP

ZHANG Kequn, SUN Huilai, LI Hang, XING Wentao, ZHAO Fangfang

2023, 0(9): 85-91. DOI: 10.19936/j.cnki.2096-8000.20230928.013

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When drilling carbon fiber composites (CFRP), the delamination damage caused by the bit axial force is one of the most important factors affecting the assembly quality and service life of parts. In order to improve the quality of CFRP hole making, this paper analyzes the influence of spindle speed, feed rate and edge diameter on the axial force of casing drill through orthogonal experiment, and establishes the regression prediction model of axial force based on response surface method (RSM). Aiming at the problem of model accuracy, a radial basis neural network (RBF) prediction model optimized by particle swarm optimization (PSO) algorithm was proposed and verified by experiments. The results show that the main factors influence the axial force in the order of feed rate > spindle speed > aperture. The combination of high speed, low feed rate and large blade diameter can obtain smaller axial force. The average relative error of the PSO-RBF neural network prediction model is 3.27%, which is 32.85% and 44.67% lower than that of the standard RBF neural network prediction model and RSM regression prediction model, respectively. Therefore, the PSO-RBF neural network model can predict the axial force in the process of casing drilling more effectively.

Micro-modeling and analysis of woven composites based on embedded constraints method

WANG Ping’an

2023, 0(9): 92-97. DOI: 10.19936/j.cnki.2096-8000.20230928.014

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In order to improve the modeling efficiency of woven composites under the premise of ensuring calculation accuracy, a finite element model of planar woven composites with embedded constraints and tie constraints is established in this paper. The strain-stress curve, stress distribution and failure propagation of the two models were studied by finite element method of progressive damage analysis. The results of the comparative analysis show that the embedded constraint model can obtain simulation results close to the tie model. The embedded constraints model can obtain different simulation accuracy through different preprocessing methods. Appropriate reduction of the properties of the matrix elements that have spatial intersections with fiber bundles can effectively improve the strength simulation accuracy. In addition, this paper presents a method for automatically determining the yarn trajectory of planar woven composites, which can further improve the modeling efficiency through programming.

Study on connection performance of Z-pin reinforced composite members

LIU Weiwei, YIN Mingxin, TENG Xuebei, JIN Kexin, YAN Bin

2023, 0(9): 98-105. DOI: 10.19936/j.cnki.2096-8000.20230928.015

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The transverse three-point bending tests were used to study the impact of Z-pin diameter and volume content on the connection performance of composite toughened simplified components. Compared to the blank control group, the payload of Z-pin toughened specimens increased by 48.41% to 96.97% and the total energy dissipation by 661.88% to 748.72% with an increase in Z-pin volume content. The results of this test show that toughened specimens’ load carrying capacity can be significantly increased by using high Z-pin volume content. The load carrying capacity of the test group with the Z-pin diameter of 0.5 mm is slightly greater than that of the test group with the Z-pin diameter of 0.3 mm, but the test group with the Z-pin diameter of 0.3 mm has better stability in the case of the same Z-pin volume content of 0.4%. According to the test results, Z-pin implantation can improve the payload and energy dissipation of the composite toughened class’s simplified members and, obviously, enhance the connection performance of the toughened specimens.

Experimental study on axial compression performance of new-type BFRP-confined square concrete columns

SHEN Huijun, ZHENG Hehui, ZHANG Feng, LI Ziqiang

2023, 0(9): 106-111. DOI: 10.19936/j.cnki.2096-8000.20230928.016

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Aiming at the new-type BFRP based on epoxy silicate resin, the confined effect on the concrete structure was studied by model test and theoretical analysis. The influence of the wrapping form and the number of layers on the mechanical properties of the square concrete column was analyzed. The results show that the development trend of the loading curve of specimens confined by BFRP and CFRP is basically the same, but the confined effect of BFRP is relatively poor. Under the two layers of full coverage, the axial compression bearing capacity of the BFRP-confined specimens and the CFRP-confined specimens is increased by 28.45% and 64.73%, respectively. The existing specifications have good applicability to CFRP reinforced specimens, but poor applicability to BFRP. The calculation model proposed in this paper can accurately predict the axial compression bearing capacity of new-type BFRP-confined square concrete columns.

Research progress in path planning for continuous carbon fiber 3D printing

ZHANG Rongyao, QIAN Bo, LIU Gang

2023, 0(9): 112-120. DOI: 10.19936/j.cnki.2096-8000.20230928.017

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In recent years, with the development of 3D printing technology, some complex geometric composite structures can be effectively manufactured, thus expanding the application scope of composite materials. Path planning is one of the key technologies in 3D printing manufacturing process. Due to the anisotropic characteristics of continuous carbon fiber, different printing paths have a great impact on the mechanical properties and forming efficiency of the molding parts. This paper mainly describes the in-plane non-interleaved printing and load-based path planning for continuous carbon fiber 3D printing. Finally, the research emphasis and development direction of 3D printing path planning are pointed out.

Research progress of medium and low temperature curing benzoxazine resins

KANG Longzhao, FAN Chunyan, YU Haiwen, YAO Yalin

2023, 0(9): 121-128. DOI: 10.19936/j.cnki.2096-8000.20230928.018

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In practical applications, the curing temperature of benzoxazine resin above 200 ℃ limits its large-scale use in the field of advanced composite materials, so it is of great significance to study the ring-opening polymerization mechanism of benzoxazine resin, optimize the curing characteristics of benzoxazine resin, and obtain the method to reduce the curing temperature of benzoxazine resin. This paper reviews the research progress on reducing the curing temperature of benzoxazine resin in recent years at home and abroad. The method of introducing active functional groups into benzoxazine monomer and adding curing catalyst to achieve medium-low temperature curing of benzoxazine resin was introduced in detail. The reaction mechanism was analyzed, the influencing factors of curing reaction were clarified, and the characteristics of the two kinds of methods were compared. From the molecular point of view, the introduction of active groups into monomers has higher flexibility, but the modification process is relatively complex. It is difficult to engineer large quantities of production. In comparison, the curing temperature of benzoxazine resin can be significantly reduced by adding a suitable curing catalyst, and the operation process is easy to achieve, which is one of the simplest and most effective methods at present. This review covers various studies on curing catalysts, providing insights for optimizing the curing conditions of benzoxazine resin and preparing high-performance benzoxazine resin materials.

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