COMPOSITES SCIENCE AND ENGINEERING

Vibration analysis of fixed-supported stiffened composite plate with embedded damping film

JI Sheng-fei, LIANG Sen, WANG Guang-he

2022, 0(11): 5-14. DOI: 10.19936/j.cnki.2096-8000.20221128.001

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To study the free vibration characteristics of composite stiffened plate with embedded damping membrane, the theory of Timoshenko Beam reinforcement strain energy and kinetic energy is deduced. Utillzing the energy method to establish the free vibration theory model of stiffened plate, it will meet four edges clamped boundary conditions of structure displacement function by Galerkin method weighted residual value ideas into double series form. The vibration differential equation of the reinforced plate structure with embedded damping film was established and the free vibration frequency and loss factor of the structure were solved. The finite element model was constructed, specimens of stiffened plate made of damped film composite material were made and the experimental platform was built. The effectiveness of the theoretical model was proved by comparing the theoretical solution, numerical simulation solution and modal experiment. At the same time, the influence of the height of stiffeners and the distance between the stiffeners on the vibration characteristics of the stiffened plate is further studied,which provides a theoretical basis for the optimal design of stiffened plate of embedded damping film composite with large damping and high stiffness.

Experimental study on the bond shear stress-slip relationship of CFRP-timber interface

LEI Yun-xiao, LIU Sheng-wei, ZHAO Jian-chang, ZHANG Jia-wei, BAI Cheng-yu

2022, 0(11): 15-19. DOI: 10.19936/j.cnki.2096-8000.20221128.002

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In order to study the mechanical properties of carbon fiber reinforced polymer (CFRP) and timber bonding interface, through the shear test of 30 (6 groups) CFRP-timber double-sided bonding specimens, the development law of CFRP strain and interface bonding shear stress was analyzed, to obtain the bonding shear stress-slip relationship curve, and explore the effect of CFRP paste length and width on the interface bonding performance. Through regression analysis of the test results, the CFRP-timber interface bonding shear stress-slip constitutive relationship model is proposed. The test results show that the specimens mainly undergo shear failure and peeling failure, and there is no obvious sign before failure, which is brittle failure. The bonding width of CFRP has a significant influence on the ultimate bearing capacity of the interface. After a certain length, the bonding length has the limit of the interface. The bearing capacity is not obvious; the polynomial-lognormal function constitutive model controlled by two parameters proposed in the article can better fit the test results; it can provide a theoretical basis and practical reference for CFRP-reinforced wooden structures.

Study on the flatwise tensile properties of honeycomb sandwich structure with plain weave faceplate

SUN Yi-gang, MA Rui-yun, WANG Xuan, CHENG Ji, ZHOU Chun-ping

2022, 0(11): 20-27. DOI: 10.19936/j.cnki.2096-8000.20221128.003

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To investigate the flatwise tensile strength of the plain weave panels honeycomb sandwich structure, ABAQUS was used to create a detailed model of the sandwich structure based on the progressive damage failure analysis methodology. The cohesion model was selected to simulate the adhesive layer between the faceplate and the honeycomb core. FORTRAN language was applied to write USDFLD subroutines describing failure and degradation criteria, which predict the flatwise tensile properties of the sandwich structure. The results show that the predicted flatwise tensile strength and failure mode are consistent with the test results, checking whether the model is correct. There is no damage between the layers of the faceplate and the adhesive layer between the faceplate-core. The honeycomb damage is mainly caused by longitudinal damage to the honeycomb wall. Damage occurs first in the middle of the core wall, then the damage spreads to both sides. Finally, the middle part of the whole honeycomb core cracks and the structure fails. The peel strengths of the layers of the faceplate and the adhesive layer between the faceplate-core are higher than the tensile strength in the longitudinal direction of the core. The deformation of the entire sandwich structure is dominated by the deformation in the longitudinal direction of the core.

Study on damage evolution of NOL-ring based on AE parameters fusion

YAN Xiao-wei, LI Wei, JIANG Peng, LIU Ying-hong-lin, CHENG Jia-hao

2022, 0(11): 28-34. DOI: 10.19936/j.cnki.2096-8000.20221128.004

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In order to evaluate the damage process of NOL-ring by acoustic emission monitoring technology, the static tension and graded loading experiments of NOL-ring in different stages are carried out in this paper. Through experimental comparison, using AE parameter fusion, R value and b value are introduced to study the NOL-ring damage process. The NOL-ring damage is divided into three stages, and different damage conditions are characterized by the change law of b value. RA value and R value are very sensitive to the early damage mode and cumulative damage change of the specimen. The results show that the b value in stage Ⅰ is larger than that in stage Ⅱ, and the R value decreases when the b value increases, indicating that there is crack propagation in the specimen. In the static tensile test, the initial R value of damage in stage Ⅰ fluctuates greatly and is complex. In stage Ⅲ of severe damage, RA value changes greatly and complex. When it exceeds 0.85F_max, b value decreases rapidly, which is mainly related to interface damage and fiber fracture. The formation of final fracture is mainly related to the propagation of main crack causing damage.

Study on the performance of multiple adhesives for single lap bonding of carbon fiber composites

LOU Shu-mei, REN Guo-dong, YANG Zhen-san, LI Yu-tong, ZHAGN Hui

2022, 0(11): 35-42. DOI: 10.19936/j.cnki.2096-8000.20221128.005

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In order to study the bonding properties of different structural adhesives on carbon fiber composite substrates, seven different structural adhesives composed of epoxy resin, acrylate and polyurethane were used to bond carbon fiber composite-carbon fiber composite (CF-CF), and the tensile and shear strength were tested at room temperature and ultimate temperatures (80 ℃, -65 ℃). In order to explore the mechanical properties and failure modes of each adhesive, and test the bonding properties of epoxy structural adhesive to different fiber types of composites (T700-12K carbon fiber composite, T300-3K carbon fiber composite and glass fiber composite) at room temperature. The bonding mechanisms of carbon fiber and glass fiber composite are explored and then the adhesive with the best performance is obtained. It provides a reference for the selection of bonding agent between carbon fiber substrates in the fields of aerospace and automobile.

The carrying capability of adhesive double-lap composite joint and the adhesive layer deformation

MA Yu, MA Bin, CHEN Xi-rui

2022, 0(11): 43-48. DOI: 10.19936/j.cnki.2096-8000.20221128.006

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The carrying capability calculation formula of adhesive double-lap composite joint has limitation, which could not completely describe the relationship between the adhesive thickness and the carrying capability. It is believed generally that the reason are defects and peel effect. Based on the existing test data, we contrastively analyzed the shear deformation and peel deformation of adhesive layer along the overlap length in the joint for different adhesive thicknesses. It is found that the carrying capability decreases, the shear deformation and peel deformation decrease along with the adhesive thickness increase. Also no peel damage and obvious defect was found. The deduction is put forwards that the main reason for the discrepancy between theory and practice is the change of the adhesive layer shearing strain energy density for controlling the adhesive thickness, and it was preliminary proved by 5 groups contrast experiments.

Study on penetration resistance of ceramic/UHMWPE composite target plates with different shapes

HUANG Hao-jie, LIANG Sen, ZHOU Yue-song

2022, 0(11): 49-53. DOI: 10.19936/j.cnki.2096-8000.20221128.007

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A kind of special-shaped composite target plate composed of SiC ceramic and UHMWPE plate is presented. Finite element software ANSYS/LS-DYNA is used to conduct numerical simulation to explore the anti-penetration performance of the target plate under the 53 type 7.62 mm armor-piercing firebomb, and the numerical simulation was verified experimentally. Furthermore, the shape and the bending radian of the target plate on the penetration resistance are further studied. The results show that the anti-penetration performance of the outer convex spherical shell target is the best, and that of the concave spherical shell is the worst. Convex curved target plate is better than concave curved target plate. The bending of the target plate increases the peak load of the ceramic panel. With the increase of the bending radian of the target plate, the residual velocity of the bullet decreases at first and then increases, and the energy absorption of the target plate increases at first and then decreases. When the central angle of the convex curved target plate is 8°, the anti-penetration performance is the best. The peak load of the ceramic panel varies greatly with the change of the bending radian of the target plate, while the peak load of the UHMWPE backplane changes little.

Low-velocity impact performance of foam sandwich structure with plain weave panel after repair

ZHOU Chun-ping, WANG Xuan, ZHANG Shi-qiu, GANG Qing-yong

2022, 0(11): 54-62. DOI: 10.19936/j.cnki.2096-8000.20221128.008

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A low-velocity impact test was carried out on the repaired plain woven foam sandwich panel to study the impact response parameters and damage mode of the repaired sandwich panel under the same impact energy and punch diameter, and the repaired sandwich panel was subjected to impact edgewise compression test to study the post-impact compressive strength, compressive modulus and residual compressive strength of sandwich panels after repair. The test results show that the maximum impact load of the test piece after repairing is generally larger. The maximum displacement of the punch is roughly the same under different repair conditions. The introduction of the repair additional layer reduces the depth of the pits caused by low-speed impact, and the drop in impact load is caused by the damage of the test piece. The damage pattern of the test piece after impact is basically the same, and the panel is mainly composed of delamination and resin matrix fragmentation. The fragmentation of the core material not only occurs at the impact site, but the core material outside the impact zone will also be broken due to uncoordinated deformation. After the test piece is subjected to low-velocity impact, the edgewise compressive strength and the remaining edgewise compressive strength percentage of the repaired piece are mostly higher than those of the unrepaired piece, but the edgewise compressive modulus is mostly lower than that of the unrepaired piece.

Study on development of element for FRP flexurally strengthened beam

XU Tian-cai, MA Sheng-qiang, DAN Dan-hui

2022, 0(11): 63-71. DOI: 10.19936/j.cnki.2096-8000.20221128.009

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Paste FRP (Fiber Reinforced Polymer) material at the bottom of the beam can greatly improve the bending stiffness of the beam, thereby reducing the deformation of the beam. In this paper, the stiffness calculation formula of FRP flexurally reinforced beams at different stages is established by the stiffness method, and the stiffness matrix of the FRP flexurally reinforced beam element is derived by the variational method, and the FRP reinforced beam element is established. Based on the basic principle of the finite element method, The numerical software is used to establish the calculation program of FRP reinforced beams, and the related experimental researches are analyzed. The results show that the stiffness calculation method of FRP reinforced beams built in this paper is too large in the stage of reinforcement before yielding after concrete cracking. By calculating the average ratio of the yield displacement test results of FRP reinforced beams to the calculated results in this work, and introducing the reduction factor of 1.377 for calibration, the calculated errors of yield deflection and ultimate deflection are within 2 mm and 8 mm, respectively, and the average errors of yield bending moment and ultimate bending moment are -3.0% and 11.4%, respectively. At the same time, the calculated load-displacement curves of each beam are in good agreement with those of the test. In this paper, the calculation results of FRP reinforced beam elements are of high accuracy, and good analysis results can be obtained, which can provide reference for engineering design.

Research on vibration damping performance of CFRP raft with different connectors

YANG Hai-ru, ZHU Yi, ZHANG Jin-guang, CHEN Guo-zhi

2022, 0(11): 72-76. DOI: 10.19936/j.cnki.2096-8000.20221128.010

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In this paper, carbon fiber reinforced plastic (CFRP) rafts with different connectors are designed. The specific damping capacity (SDC) of CFRP rafts with different connectors is calculated by using ABAQUS finite element analysis and MATLAB software. Experimental is carried out to verify the accuracy of the calculation results of raft SDC. The results show that the SDC of CFRP raft with combined H-shaped connector is better, and its damping performance in low frequency is better than that of integral connector raft, which provides theoretical guidance for the design of raft.

Effect of linear epoxy surface modifiers on properties of nylon/carbon fiber composites

ZHU Min-jie, WEI Long-sha, YAN Yi-wu

2022, 0(11): 77-81. DOI: 10.19936/j.cnki.2096-8000.20221128.011

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Due to the poor interfacial adhesion between the carbon fiber and nylon, linear epoxy polymer and polyamide block linear epoxy were synthestized as reactants. And the carbon fiber without desizing was modified by above synthetic products, respectively. Secondly, nylon/carbon fiber composites were prepared, and the effect of surface modifiers on the properties of nylon/carbon fiber composites was studied by surface energy, mechanical properties and SEM. The results showed that the surface roughness of carbon fiber was increased by the modification of linear epoxy and its block polymer, and the dispersion component of surface energy of carbon fiber was increased from 5.63 mN/m to 22.64 mN/m. Furthermore, the bending strength and interlaminar shear strength of the composites were increased by 74.8% and 115.8%, respectively.

Mechanical and electromechanical behaviors of heating grid with hybrid fiber

PENG Zhe-qi, WANG Xin, LIANG Xun-mei, ZHAO Chun-feng, SHEN Jun-qian

2022, 0(11): 82-89. DOI: 10.19936/j.cnki.2096-8000.20221128.012

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As the traditional snow melting and ice melting methods have problems such as time-consuming, labor-intensive and environmental pollution, using hybrid-fiber heating grid in the road pavement to melt snow with both reinforcement and electrothermal advantages has become an important research direction in recent years. In this study, the static tensile properties and electromechanical behaviors of carbon fiber heating core and hybrid fiber heating grid were investigated, including six types of carbon fiber impregnated roving, with three types of matrices (epoxy/SBL/polyurethane) and two weaving forms (untwisted/twisted), warp/weft basalt fiber grid, hybrid fiber heating grid. The results showed that the integrative behavior of polyurethane resin twisted carbon roving and basalt fiber grid was satisfactory. The elastic modulus of hybrid fiber heating grid was 87 GPa and the strength utilization efficiency was 93.6%. The resistance changing rate between 0~10 000 με maintained within 1%, which can meet the requirements of engineering applications.

Preparation and properties of carbon fabric reinforced modified BMI composites

ZHANG Hui, WANG Lin-xiang, ZHENG Qing, YUAN Qiao-long, HUANG Fa-rong

2022, 0(11): 90-95. DOI: 10.19936/j.cnki.2096-8000.20221128.013

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4,4'-Dipropargyloxydiphenyl ether (DPEDPE) and N-(3-ethynylphenyl) maleimide (3-EPM) were synthesized as alkynyl-containing modifiers to blend with diphenylmethane bismaleimide (BDM) and diallyl bisphenol A (DABPA) system to prepare modified bismaleimide resins in melting method. The processability, thermal stability, and mechanical properties of alkynyl-containing compounds modified BDM/DABPA resins were studied. The carbon fabric reinforced modified BDM/DABPA composites were molded by hot-press. The thermal-mechanical properties of the composites were also studied. The results show that DPEDPE can broaden the processing window of BDM/DABPA resin. The alkynyl-containing compounds modified BDM/DABPA resins can dissolve in polar solvents except ethanol. The temperature of 5% weight loss (T_d5) and residual yield at 800 ℃ (Y_{r 800 ℃}) in N₂, and glass transition temperature (T_g) of the cured 3-EPM modified BDM/DABPA resin can reach 426 ℃, 37.3% and above 380 ℃, respectively. The tensile strength of the cured BDM/DABPA decreases with addition of DPEDEP or 3-EPM. However, the impact strength of the cured DPEDPE-modified BDM/DABPA can increase to 19.6 kJ·m^-2. The T300 carbon fabric reinforced DPEDPE-modified BDM/DABPA composite possesses the flexural strength of 547 MPa and interlamellar shear strength (ILSS) of 32.8 MPa at room temperature, and retains the strength of 98% at 200 ℃. The flexural strength and ILSS of the composite can keep the flexural strength of the composite for 90%, and ILSS of the composite for 82% at 250 ℃, respectively.

Icing condition prediction of wind turbine blade based on neural network technology

MA Fei-yu, ZHANG Chun-zhi, LI Fei-yu

2022, 0(11): 96-101. DOI: 10.19936/j.cnki.2096-8000.20221128.014

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Wind turbine blades installed in cold areas are inevitably covered with ice, which affects the normal operation of wind turbines. The natural frequencies of blades vary with the locations and mass of icing. In this paper, the finite element modal analysis of 2 MW wind turbine blade is carried out, and the relationships between the change rate of natural frequency of ice-covered blade and the mass of ice-covered blade at different positions are constructed. The BP artificial neural network is trained with this data set and the prediction ability is analyzed. The research shows that the average relative error rate of predicting all ice-covered blades is 13.21%, which is 1.56% higher than the prediction accuracy of Gantasala et al., by using the relational training artificial neural network which is constructed considering the influence degree of different ice-covered locations on the natural frequency of all ice-covered leaves. The trained artificial neural network model can predict the locations and mass of icing. The result can provide data support for subsequent heating or ultrasonic deicing and improve deicing efficiency and reduce energy consumption.

Study on compression and permeability characteristics of thick layer-up reinforcements under VARTM process

LI Zhe, LI Wei

2022, 0(11): 102-106. DOI: 10.19936/j.cnki.2096-8000.20221128.015

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In order to study the permeability and compression characteristics of thick layer-up fabrics, the fabrics with different plies were measured by radical permeability and unidirectional permeability teat method. The change of fabric thickness during radical permeability test was used to analyze the compression characteristics of thick layer-up fabric. The results indicate that the permeability of thick layer-up fabric is greatly affected by the thickness of fabric. As the thickness of the fabric layer increases, the permeability of the fabric in all directions decreases; when the VARTM is used to make thick layer-up composite, the thickness of fabric changes with the process. The thickness of the fabric is mainly affected by the gaps between the layers and fiber pores during the vacuum. The thickness of layer-up fabric is affected by the fiber state during the infusion. The research results provide references for the refined manufacturing of large-scale thick layer-up composite.

Study on the influence mechanism of phosphorus-containing flame retardants on the flame retardant and thermal properties of epoxy resin

WANG Shu-xia, CHEN Feng, YAO Li-chao, ZHAI Jun-ming

2022, 0(11): 107-113. DOI: 10.19936/j.cnki.2096-8000.20221128.016

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Aiming at the problem that epoxy resin is flammable and emits a large amount of smoke, green and environmentally friendly organophosphorus flame retardants are used to realize the flame retardant modification of epoxy resin. The curing process of the resin system is studied by the rotational viscosity method and the DSC method, and determine the curing system. The curing kinetic analysis method is used to determine the curing kinetic equation of the epoxy resin. DMA, TG and combustion tests are used to study the glass transition temperature, thermal performance and flame retardancy of the epoxy resin by the organic phosphorus flame retardant performance impact. The results show that when 10~15 parts of flame retardant are added, the flame retardant grade of epoxy resin casting body reaches V-0, the limiting oxygen index reaches 29.3%~32.1%, the storage modulus increases, the amount of carbon residue increases, and the glass transition temperature has dropped to a certain extent. Further analysis shows that the organic phosphorus flame retardant has the dual flame retardant effect of gas phase and condensed phase on epoxy resin.

Mechanical properties of domestic CCF800H carbon fiber reinforced high temperature resistant BMI matrix composites

WANG Ying-fen, PAN Cui-hong, ZHOU Hong-fei, SUN Zhan-hong

2022, 0(11): 114-119. DOI: 10.19936/j.cnki.2096-8000.20221128.017

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CCF800H/QY260E high temperature resistant composites were prepared by hot melt mixing prepreg using autoclave processing. The viscosity-temperature property of QY260E was studied, and then the interfacial properties, toughness and hydrothermal-resistant properties of domestic CCF800H/QY260E composite were synthetically investigated by the scanning electronic microscopy (SEM), glass transition temperature (T_g) determination before and after moisture absorption, basic mechanical properties tests and fracture morphology analysis. The results show that QY260E bismaleimide composite possesses longer temperature and time range at low viscosity. The saturation hygroscopicity rate of CCF800H/QY260E is only 0.66%, and its T_g descends only 21 ℃ after 14 days at 71 ℃ immertion. In addition, the retention ratio of 0° tensile strength is above 80% and the open hole tensile strength is above 90% at 230 ℃/humidity. The retention ratio of 0° tensile strength is above 70% and the open hole tensile strength is above 90% at 260 ℃/humidity. The retention ratio of interfacial shear strength and open hole compression strength are above 40% at 230 ℃/humidity and 260 ℃/humidity. The CAI value of CCF800H/QY260E is close to foreign advanced composite IM7/5250-4. Tight connection between fiber and resin is observed from fracture morphology of 90°tensile samples and interlaminar shear samples. Therefore, all the results indicate that the CCF800H/QY260E composite has good mechanical properties and hydrothermal-resistant properties.

A review of prediction methods of process-induced distortions in thermoset composites based on artificial neural network

LUO Ling, TIAN Zhi-li, ZHANG Tao, LIU Lei-bo, LI Zhuo-da, LI Li-ying

2022, 0(11): 120-127. DOI: 10.19936/j.cnki.2096-8000.20221128.018

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Thermosetting-matrix composites have become attractive in aerospace industry on account of their numerous advantages over conventional materials, such as their intriguing physical and mechanical properties, and their designable ability in terms of the design process and the subsequent manufacturing process. Despite these benefits, process-induced distortion is crucial issue since it cause assembly difficulties and residual stresses. This paper aimed at reporting the current research status of the process-induced distortion behavior of thermosetting-matrix composites, which was introduced during the hot forming process. The process-induced distortion mechanism, the related numerical simulation method, artificial neural network method and its application in the process-induced distortion were mainly introduced. An emphasis being placed on the state-of-art development of high-throughput prediction and inverse design of process-induced distortions based on artificial neural network. Finally, the future development directions of process-induced distortion and artificial neural network were briefly discussed.

Research progress on phenolic impregnated carbon fiber ablation composite

BU Tong-an, TIAN Mou-feng, SONG Han, REN Liang

2022, 0(11): 128-132. DOI: 10.19936/j.cnki.2096-8000.20221128.019

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The development of hypersonic aircraft, high Mach number spacecraft return capsule and deep space exploration has brought new demands of the performance of thermal protection materials. Lightweight carbonized materials have emerged and gradually become key materials in the field of thermal protection. Phenolic impregnated carbon fiber ablation body (phenolic impregnated carbon ablator, PICA) is a typical representative of lightweight carbonized materials. This article reviews the progress of PICA materials. Firstly, it summarizes the classification of PICA materials and its ablation mechanism; secondly, it summarizes the modification of PICA materials; finally, it looks forward to the development trend of PICA materials.

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