COMPOSITES SCIENCE AND ENGINEERING

THE ANALYSIS OF ELASTOPLASTIC PROPERTIES OF HIGH VOLUME FRACTION PARTICLE REINFORCED COMPOSITES

SUN Ke-ke, MA Lian-hua, CAO Ya-kuo, ZHU Si-xian

2021, 0(4): 5-11. DOI: 10.19936/j.cnki.2096-8000.20210428.001

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The composites reinforced by particles with high volume fraction are widely used in engineering field. In this work, the elastoplastic micromechanical model is established for such composites, and the macroscopic elastoplastic mechanical properties under uniaxial tension and compression are systematically studied. In the aspect of effective modulus prediction, the Mori-Tanaka model and the interaction micromechanics model proposed by Ju et al. are employed to study the effective modulus of the particle reinforced composites with high volume fraction, and the limitations of the Mori-Tanaka model are addressed. For the particle reinforced composites with high volume fraction, the Hill's theorem and the field fluctuation method are employed to formulate the relationship between the macroscopic stress and the equivalent stress of the matrix. Within the theoretical framework, the Mori-Tanaka model and Ju's model are respectively used to study the macroscopic elastoplastic properties of such material with different particle volume fraction. The comparisons between the theoretical prediction with experimental data and finite element simulation results are made. The results show that, for the macro-elastoplastic properties of high volume fraction particle reinforced composites, the prediction results of the proposed model are more accurate than those of the traditional model, and such model may provide a theoretical reference for the prediction of the elastoplastic properties of such materials in the engineering field.

FLEXURAL BEHAVIOR OF HIGH-STRENGTH CONCRETE BEAMS REINFORCED WITH CFRP BARS AND HIGH-STRENGTH STEEL BARS

WANG Zuo-hu, SHAO Ming-zhe, LIU Du, YANG Ju

2021, 0(4): 12-17. DOI: 10.19936/j.cnki.2096-8000.20210428.002

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Carbon fiber reinforced composite materials (CFRP) bars and high-strength steel reinforcement mixed in the high-strength concrete beams, can better exert the properties of the material and improve the utilization of building materials. In this paper, bending tests were carried out on high-strength concrete beams with CFRP bars and high-strength steel bars, and the theoretical calculation of its flexural capacity was derived. The results show that all the specimens exhibit typical ductile failure characteristics. Under the condition of the same nominal reinforcement ratio, compared with high-strength concrete beam with high-strength steel bars, the ultimate load of the mixed reinforced high-strength concrete beam is reduced by 15%, but the ultimate displacement is increased by 34%. Compared with high-strength concrete specimen, the yielding load and ultimate load of steel fiber high-strength concrete specimen are increased by 12.6% and 15.8%, respectively.

INFLUENCE OF STRUCTURAL PARAMETERS OF COMPOSITE DOUBLE-BOLT HYBRID BOLTED/BONDED JOINTS ON FAILURE LOAD

ZHENG Yan-ping, LI Ming-kun, XIONG Yong-jian, ZHANG Chao-yu

2021, 0(4): 18-27. DOI: 10.19936/j.cnki.2096-8000.20210428.003

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Based on the experimental verification of the feasibility of the simulation model, numerical simulation methods are used to explore the influence of the composite material layering sequence, the width-to-diameter ratio, end-diameter ratio, and aperture ratio of the hybrid connection structure on the bearing capacity of the titanium alloy-composite double-bolt hybrid bolted/bonded joints on failure load. The research results show that among the commonly used layup sequences, when the layup sequence is [45°/0°/-45°/90°]_3s, the load-bearing capacity of the hybrid connection structure is the best. As the aspect ratio increases, the failure load of the connection structure will gradually increase, but the connection strength will gradually decrease. Within a certain range, an appropriate increase in the end diameter ratio or aperture ratio can increase the carrying capacity of the connection structure, and when it exceeds this range, the carrying capacity of the connection structure will decrease.

STUDY ON THE MECHANICAL PROPERTIES AND FAILURE CHARACTERISTICS OF LIGHTWEIGHT AGGREGATE FIBER SHOTCRETE

SUN Qiu-rong, LIU Lei

2021, 0(4): 28-34. DOI: 10.19936/j.cnki.2096-8000.20210428.004

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On the basis of the shotcrete ratio, the 3 different amounts of ceramsite and basalt fiber are combined. Nine groups of Lightweight Aggregate Fiber Shotcrete (LAFS) were prepared to explore the influence of ceramsite and basalt fiber on the compression, tensile and shear strength of LAFS. Based on the test results, a LAFS strength prediction model was established. At the same time, with the help of RFPA^2D software simulation, the force characteristics and failure laws of ceramsite and basalt fiber in the process of LAFS are obtained. The results show that the content of ceramsite and basalt fiber has an interactive effect on the compressive, tensile and shear strength of LAFS. Test analysis shows that the LAFS performance is the best when ceramsite is mixed with 116.248 kg/m³ and basalt fiber is mixed with 5.26 kg/m³. Adequate bonding of ceramsite and LAFS is the key to ensure the strength of LAFS. The fiber has good integrity during the LAFS stress process. Before LAFS breaks, it can bear the force together with the concrete matrix. This research can provide experimental and theoretical basis for the development of LAFS in engineering.

PREDICTION AND EXPERIMENTAL VERIFICATION OF THREE-DIMENSIONAL WOVEN COMPOSITE PREFORM FIBER VOLUME FRACTION

LI Chun-hui, HE Lei, WANG Zheng-fang, CHENG Xiang

2021, 0(4): 35-40. DOI: 10.19936/j.cnki.2096-8000.20210428.005

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Fiber volume fraction is an important indicator for the design and analysis of three-dimensional woven composites, and has a great influence on the impregnation process and material properties of composites. In order to determine the fiber volume fraction of the three-dimensional woven composite preform, the meso-structure model of the quadrilateral and triangular preforms was established. The preform is divided into unit cell forms such as interior cell, side cell, corner cell, etc. The unit cell type coefficient is determined and the preform is represented by a matrix according to the unit cell arrangement. The fiber volume fraction of the preform is calculated by the unit cell type coefficient matrix and the unit cell volume. The fiber volume fraction theoretical value is compared with the actual measured value obtained by the weighing method. The results show that the theoretical calculation model of preform fiber volume fraction is accurate, and the error is controlled within 4%. The fiber volume fraction increases with the increase in the number of fiber strands in the Z direction, and decreases with the increase of the size. When the size increases to a certain value, the fiber volume fraction approaches the same. The measured value of fiber volume fraction decreases with the increase of the number of weaving layers and the number of fiber strands in the horizontal plane. Finally, the possible reasons for the above conclusions are analyzed. This calculation method can provide a theoretical reference for the prediction of fiber volume fraction of arbitrary shape preforms.

STUDY ON THE RELATIONSHIP BETWEEN BENDING CHARACTERISTICS AND TEMPERATURE OF COMPOSITE HONEYCOMB SANDWICH REPAIR STRUCTURE

YU Fen, GUO Tuo, HE Zhen-peng, DAN Min

2021, 0(4): 41-49. DOI: 10.19936/j.cnki.2096-8000.20210428.006

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The progressive damage analysis model of composite honeycomb sandwich repair structure is established, and the ultimate bearing capacity and damage failure mode of repaired honeycomb sandwich structure under bending load are studied, and the correlation between bending performance and temperature of repaired structure is further studied. By programming the VUMAT subroutine, setting the failure criteria and stiffness degradation mode of the patch and honeycomb damaged plate, and using the cohesive element to simulate the repair adhesive layer, the progressive damage analysis of composite honeycomb sandwich repair structure was completed. The results show that the bending bearing capacity of the structure and the bonding capacity of the adhesive layer are greatly affected by the temperature, the bending strength of the structure decreases with the increase of the temperature, and the debonding failure will damage the structural integrity. The matrix damage of the honeycomb sandwich panel first occurs at the 90° ply, and the fiber matrix shear damage first occurs at the 0° ply, and extends to the free boundary.

DESIGN METHOD AND PERFORMANCE ANALYSIS OF A COMPOSITE MOULD SURFACE STRESS-STRAIN MONITORING MODULE BASED ON BUILT-IN FBG

HUANG Shang-hong, YAN Chen, LI Rui-ying, LI Yi-quan

2021, 0(4): 50-54. DOI: 10.19936/j.cnki.2096-8000.20210428.007

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This paper introduces a kind of built-in fiber Bragg grating (FBG) sensor module of composite mould. Firstly, the linear strain sensitivity of the sensor module is calibrated under the vertical concentrated static pressure. By analyzing the modal buckling of the sensor module, the service stability of the sensor module under the built-in condition is determined. After that, the module is applied to the mould surface monitoring process of large-scale wind turbine blades. In the process of adjusting the mould surface, the deflection displacement vector collected by the laser tracker is compared with the vertical component strain obtained by the sensor module, and finally the performance of the module is verified to meet the practical application feasibility.

FROST RESISTANCE AND DAMAGE DEGRADATION MODEL OF BASALT FIBER REGENERATED CONCRETE

XIE Guo-liang, SHEN Xiang-dong, LIU Jin-yun, ZHANG Bin

2021, 0(4): 55-60. DOI: 10.19936/j.cnki.2096-8000.20210428.008

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In order to study the frost resistance of fiber recycled concrete, improve the service life of recycled concrete structures in cold areas. Five groups of recycled concrete with different basalt fiber content were prepared by using equal volume recycled aggregate instead of gravel. The damage deterioration law of frost resistance of recycled concrete with fiber was discussed from the aspects of mass loss rate, relative dynamic elastic modulus, compressive strength and tensile strength. The research results show that: At the beginning of freezing and thawing, the mass loss rate of recycled concrete exhibits a negative growth phenomenon, and the relative dynamic elastic modulus, compressive strength and tensile strength curves show a downward trend with the increase of the number of freezing and thawing cycles; the addition of basalt fiber can slow down the freezing of recycled concrete. When thawing failure, the frost resistance of recycled concrete is the best when the dosage is 1.2 kg·m^-3; the effect of fiber addition on the tensile strength of recycled concrete under freeze-thaw action is better than compressive strength. A linear and polynomial damage degradation model based on relative dynamic elastic modulus and strength as damage variables is established. The model can accurately predict the degree of freeze-thaw damage and degradation of fiber recycled concrete.

EFFECT OF EMULSIFIER ON PROPERTIES OF THERMOPLASTIC WATER DISPERSIBLE EMULSION SIZING AGENT

LI Jia-le, LI Nan, HU Fang-yuan, JIAN Xi-gao, LIU Cheng, WANG Jin-yan

2021, 0(4): 61-65. DOI: 10.19936/j.cnki.2096-8000.20210428.009

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In this work, different surfactants are used to prepare phthalene co-polyaryl ether sulfone (PPBES) water-dispersible emulsion sizing agent by the emulsion/solution evaporation method to improve the interface compatibility between the carbon fiber and PPBES resin in high-performance thermoplastic composites. In order to obtain the best sizing effect, the effects of PPBES concentration, emulsifier type and concentration on the average concentration of sizing agent were studied. The film forming ability of the sizing agent was analyzed by scanning electron microscope (SEM), and the effect of sizing treatment on the properties of carbon fiber was studied. The results showed that the flexural strength of CFs/PPBES composites prepared by carbon fiber after sizing is up to 1781 MPa, which is 15.6% higher than that of composites prepared by non-sizing CFs, and the interface shear strength is increased by 5.0%.

STUDY ON BULLETPRO OF PERFORMANCE OF CERAMIC/UHMWPE LAMINATE/DAMPING MATERIAL COMPOSITE TARGET

ZHOU Yue-song, LIANG Sen, WANG De-pan, LIU Long

2021, 0(4): 66-74. DOI: 10.19936/j.cnki.2096-8000.20210428.010

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A kind of composite target composed of boron carbide ceramic, UHMWPE laminate and damping material is proposed. The numerical simulation analysis is carried out by using LS-DYNA dynamics software to investigate the performance of the target under the high-speed impact of 12.7 mm armour-piercing explosive incendiary projectile, and the feasibility of the numerical simulation is verified by experiments. The relationship between the anti-penetration performance of the target plate and the structural geometric parameters is further studied, and the optimum distribution position and thickness of the damping material are explored. The results show that with the increase of ceramic thickness, the kinetic energy of the target plate and the ballistic performance index increase linearly, and when the thickness of UHMWPE laminate is larger, the anti-penetration performance of target plate is improved more obviously by increasing its thickness. Under the condition of the same area density, compared with increasing the thickness of ceramic or UHMWPE laminates, the ballistic performance index of the composite target plate is the highest and the resistance to high-speed penetration is the best when it is coated with 1 mm back-layerdamping material, which lays a foundation for the wide application of damping material as damping layer in the field of high-speed impact resistance.

THE NUMERICAL ANALYSIS OF LOADED AND CONSTRUCTION PROCESS OF A FLEXIBLE PREFABRICATED MASONRY ARCH BRIDGE BASED ON CFRP

WEN Yu-li, PAN Mei-ping, XIA Li-peng, ZHENG Yu

2021, 0(4): 75-82. DOI: 10.19936/j.cnki.2096-8000.20210428.011

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With the characteristics of fiber reinforced plastic (FRP) of high tensile strength and durability, a flexible prefabricated arch bridge system based on CFRP was developed, which is not only good at load and durability, but less construction difficulty and dangerous than traditional masonry arch bridge. For discussing the feasibility of prefabricated masonry arch bridge, the processes of loading and construction of the arch bridge were modelled via ABAQUS. The FEA model of arch bridge was verified and its failure mechanism was analyzed by comparing the result of numerical simulation and experiments. The results of FEA showed that flexible prefabricated arch bridge possessed great loading-carrying capacity and third span is the most unfavorable loading location. Furthermore, the numerical results of stress distribution of CFRP and axis deformation of flexible prefabricated arch system in different lifting programs showed that CFRP can reinforce the stability of arch bridge obviously and assembly performance is severely optimized by the No.7 lifting programs, providing a reference for the design and construction control of this kinds of flexible arch bridge.

ACCURACY RESEARCH ON FULL-SCALE TEST OF LARGE WIND TURBINE BLADE

LI Cheng-liang, ZHANG Jin-feng, ZHANG Deng-gang, LI Zhan-ying

2021, 0(4): 83-88. DOI: 10.19936/j.cnki.2096-8000.20210428.012

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Structural testing is a necessary means to test the consistency and accuracy of the design of the blade product. Thus, accurately verifying the structural characteristics of large blades has become a key link in improving the reliability of blade structure design and manufacturing. Research on how to improve the full-scale test accuracy of large blades is studied from theoretical modeling analysis, static loading methods, fatigue loading methods and deformation, strain, and frequency measurement. Methods and means of high accuracy of test results are obtained through comparative analysis.

MANUFACTURING AND VIRTUAL TEST MODEL OF PMI FOAM SANDWICH COMPOSITE STRUCTURES

YUAN Chong-xin, DONG Qing-hai, HE Bin

2021, 0(4): 89-92. DOI: 10.19936/j.cnki.2096-8000.20210428.013

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Due to its high mechanical properties and processing stability, the polyimide foam sandwich structure has been widely used in aerospace. At present, the sandwich structure is mainly manufactured using the prepreg and is cured in the autoclave. This process is relatively high-cost and only provides the surface quality of the die surface. In this paper, a closed-mold liquid molding process is used to manufacture a foam sandwich structure. The simultaneous injection and alternate injection are compared. The results show that alternate injection can obtain better molding quality. In addition, the mechanical properties of the foam were tested. On this basis, the failure model of the foam was established, and its mechanical properties such as three-point bending and lateral compression buckling were carried out by finite element method. These finite element models have been verified by actual experiments and revealed the failure mechanism of the sandwich structure under these loading conditions. The research results can promote the low-cost preparation of high-performance aviation composite sandwich structures and the prediction of structural performance.

EXPERIMENTAL AND NUMERICAL ANALYSIS OF THE EFFECT OF ASSEMBLY STRESS ON THE COMPOSITE STIFFENED PANEL FAILURE

WANG Shi-jie, CHEN Zhen, XU Peng, LIU Xiao-lin, WANG Hai

2021, 0(4): 96-101. DOI: 10.19936/j.cnki.2096-8000.20210428.014

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Composite laminates are anisotropic and discontinuous along the thickness. Interlaminar stress exists in the composite laminate under out-plane loading. Delamination would happen where the out-plane stress is over interlaminate strength. In order to study the effect of out-of-plane compression load on the failure behavior of stiffened wall structure, corresponding experimental and numerical analyses were performed. Firstly, the failure load and failure mode of the specimens were obtained by the static loading test for the stiffened wall structure. Secondly, the structures were loaded to the working load through the bolts and maintained for a certain period of time. Finally, the finite element method was utilized to analyze the stress distribution of the structures. The results show that co-bonded area debonding and edge strip delamination would occur under the static load, slightly delamination was detected in the lower edge strip of the truss under the working load, and the qualitative agreement between the experimental and the numerical results was reasonably good. The research results provided references for the assembly operation specification and laminate design verification of composite structure.

THE RESEARCH ON THE DAMPING SENSITIVE PARAMETERS OF COMPOSITE LAMINATE

WU Hai-peng

2021, 0(4): 102-106. DOI: 10.19936/j.cnki.2096-8000.20210428.015

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This article aims at the sensitivity analyzing of the performance parameter of composite laminate combined with cantilever beam vibration test and strain energy finite element simulation to cross authenticate. The test result shows that the fiber type, fiber volume content, fiber angle and loading frequency are all important parameters which influence the damping performance of composites. Fiber angle and loading frequency show significant influence on composites. Meanwhile, the strain energy finite element method this article used is fitting well with the test result and can be used to estimate the damping factor of composite laminate under different fiber angles.

AUTOMATED ULTRASONIC C SCANNING INSPECTION OF BONDING QUALITY OF COMPOSITE SHELL OF SOLID ROCKET MOTOR

SHENG Tao, ZHENG Jin-hua, FENG Jun-wei, YU Na, QIAN Yun-xiang, XU Hong-jie

2021, 0(4): 107-110. DOI: 10.19936/j.cnki.2096-8000.20210428.016

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In order to solve the problems of poor traceability of test results and failure of real-time preservation of test waveforms when manual ultrasonic A-scan is used to test the bonding quality of combustion chamber shell and thermal insulation layer of a solid rocket motor, an automatic ultrasonic C-scan inspection system for bonding quality of composite shell is designed and developed. Implementing inspection work with this system reduces manual operations, improves inspection efficiency, and improves the reliability of inspection results.

TENSILE PROPERTIES PREDICTION OF NEEDLE-PUNCHING COMPOSITES BASED ON BRAIDED STRUCTURE

FU Jin-yi, SUN Xiang-chun

2021, 0(4): 111-118. DOI: 10.19936/j.cnki.2096-8000.20210428.017

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Based on the microscopic structure of needle-punching quartz/quartz composite material, a representative volume elements considering the weaving structure was established. Then by introducing periodic boundary conditions and Voxel mesh, the finite element analysis model of the RVE is established. Assuming that the nonlinear mechanical behavior of needle-punching composites is mainly generated by the matrix, the effect of needling process is equivalent to the change of the matrix properties of composites. In order to do this, the properties of the matrix were modified using the J2 plastic model. Maximum principal stress criterion, Mises stress criterion and Tsai-Wu failure criterion were used as the failure criteria for each component. And, according to the different failure modes of fiber bundles, the stiffness reduction was conducted in the failed elements. The progressive damage process of needle-punching quartz/quartz composite material under uniaxial tensile load was simulated. The simulation results are in good agreement with the test curve, and the modified matrix shows the nonlinear characteristics of the needling composite well. On the basis of the above work, the influence of braiding angle on the tensile properties of the composite was analyzed. This dissertation would be helpful to guide the manufacturing and design of needle-punching composite material in the engineering.

RESEARCH PROGRESS IN PULTRUSION COMBINATION TECHNOLOGY OF FIBER REINFORCED COMPOSITE BAR

FU Cheng-long

2021, 0(4): 119-123. DOI: 10.19936/j.cnki.2096-8000.20210428.018

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FRP bars have the advantages of light weight, high strength, corrosion resistance and good fatigue performance, etc., which have a wide application prospect in the field of civil engineering. The paper introduces the application background and preparation process of FRP bars, and mainly summarizes the research situation of several combined processes used in the preparation of FRP bars, including injection pultrusion, winding pultrusion and braiding pultrusion. The future of developments in these fields is pointed out.

ANALYSIS OF DEVELOPMENT PROSPECTS AND RESEARCH STATUS OF COMPOSITE FUEL CELL BIPOLAR PLATES

MENG Hao-yu, TANG Ze-hui, YAN Cheng-lei, AN Xin

2021, 0(4): 124-128. DOI: 10.19936/j.cnki.2096-8000.20210428.019

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Fuel cell, as a new type of power generation method, can solve two major problems of cleanliness and environmental protection at the same time, and has a very broad application prospect. As a key component of a fuel cell, the performance of the bipolar plate seriously affects the service life and related performance of the fuel cell. The composite material bipolar plate has become a research hotspot of many scholars because of its strong designability, low material cost and stable performance. This paper comprehensively analyzes the types of composite bipolar plates, as well as the research status of bipolar plates, and does some analysis and prospects on its development prospects.

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