COMPOSITES SCIENCE AND ENGINEERING

LOAD EFFECT CALCULATION AND ANALYSIS OF CFRP-OFBG PLATE EMBEDDED REINFORCED CONCRETE BEAM

DENG Lang-ni, XIE Hong, LIU Yang, MA Jin-chao

2020, 0(3): 5-10.

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CFRP-OFBG slab has good monitoring performance, and the monitoring data can be used to calculate and analyze the load effect of reinforced structures. Based on the plane cross-section assumption and the constitutive relation of stress and strain, a load calculation method for strengthened beams based on CFRP-OFBG slab strain monitoring is presented. The flexural capacity test of 4 CFRP-OFBG slabs embedded reinforced concrete beams was carried out to verify the proposed method. The results show that the calculated value is in good agreement with the test value, and the method is feasible to analyze the real-time load effect of reinforced beams.

THE INFLUENCE OF THE INTERNAL STRUCTURE OF BI-AXIAL WARP KNITTING FABRICS ON THREE DIMENSIONAL PERMEABILITY

GENG Yi, JIANG Jin-hua, CHEN Nan-liang

2020, 0(3): 11-17.

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In order to study the influence of the internal structure of the bi-axial warp knitting fabric on the permeability, a three-dimensional permeability test was performed on a plurality of biaxial fabric preforms with different structures by a 3D permeability test device integrated by image acquisition system and resin flow simulation software. The effects of suture structure and density, fiber bundle fineness, binder coating and other parameters of the biaxial fabric on permeability were analyzed by comparing the variations of in-plane and thickness directions permeabilities. The experimental results show that the in-plane permeability of the fabric with suture structure is lower than that of the automated fiber placement fabric, and the permeability in the thickness direction is much higher than that of the automated fiber placement fabric. Compared with the woven fabric, the warp knitted fabric has a higher in-plane permeability; and the variation of in-plane permeability caused by the variation of the fineness of the fiber bundle in the warp knitted fabric is closely related to the tow compression states. For the fabric with binder surface, the in-plane permeability is reduced while the permeability in the thickness direction is greatly improved.

EXPERIMENTAL STUDY ON CIRCULATING EXPANSION PERFORMANCE OF COMPOSITE MATERIAL WRAPPING SYSTEM FOR MAIN CABLE PROTECTION OF SUSPENSION BRIDGE

GU Liu-yong, FANG Hai, LI Cheng-lin, LIU Wei-qing

2020, 0(3): 18-25.

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In this paper, a prepreg fiber-reinforced composite material combined with nitrile rubber is used to design a combined wrapping system for the protection of the main cable of a suspension bridge, and the circumferential expansion performance of the system is experimentally studied. Comparative analysis of the differences in the failure modes of each group of components, most of the components fracture vertically at the overlap transition. Based on the hoop bearing capacity-radial displacement curve, the effects of changes in the number of prepreg layers and rubber band layers on the hoop bearing capacity and radial displacement of the component can be obtained. The increase in the number of prepreg layers has the largest contribution to the bearing capacity of the hoop component, with a growth rate of 65.31%-109.01%; the increase in the number of rubber band layers has the most significant effect on the radial displacement of the component, with a growth rate of 7.06%-23.5%. According to the analysis of the component′s circumferential strain-radial displacement curve, it can be seen that the compaction of the component by the loading device at the initial stage of the test results in small strains in the various parts, and the strain value of the component increases approximately linearly during loading, with the overlap strain being the smallest. The addition of rubber bands can increase the deformation of the main cable, and the protection system has more deformation redundancy, which delays the arrival of the ultimate strain of the outer prepreg wrapping tape.

FINE CHARACTERIZATION OF THE FIBER DISTRIBUTION OF SHORT CARBON FIBER REINFORCED PLASTIC

HUANG Zhen-yuan, CHENG Bin, ZHAO Ya-meng, CHEN Yi

2020, 0(3): 26-30.

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Carbon fiber reinforced plastic is a new high-quality lightweight material in recent years. It has good mechanical properties and is widely used in the automotive, electronics and other industries. Short carbon fiber reinforced plastics are usually injection molded and their properties are closely related to fiber distribution. In order to deepen the understanding of the internal fiber distribution of staple fiber carbon fiber reinforced plastics, SEM and X-ray tomography tests were carried out. The fiber extraction hole diameter, the projected length of the flow plane fiber and the distribution of fiber orientation were obtained by image processing technology, and the law of fiber orientation distribution was further verified by comparison with the Moldex simulation results. The results show that the fiber extraction hole diameter distribution of carbon fiber reinforced plastics is not affected by the fiber content. The overall orientation of fiber orientation is the flow direction, and the orientation probability along the flow direction increases first and then decreases with the decrease of the distance from the plane to the core layer. In the case of carbon fiber reinforced plastic injection molding, the areas with a higher orientation ratio in the flow direction are located in the middle of the skin layer and the core layer.

ACOUSTIC EMISSION MONITORING OF TRANSVERSE DEFORMATION AND DAMAGE OF CARBON FIBER 3D BRAIDED COMPOSITES

ZHANG Yan-jing, WEI Zhi-yuan, LIU Hai-tao, ZHOU Wei

2020, 0(3): 31-36.

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Combine with the fracture morphology, Acoustic Emission (AE) technology and Digital Image Correlation (DIC) method were used to study the law of deformation and damage of three-dimensional (3D) five-directional braided composites under transverse tensile condition. Transverse tensile mechanical response, AE characteristic parameters and deformation field information were analyzed. The results show that the limit load for 3D five-directional braided composites under transverse tensile condition is relatively low and the mechanical curve is divided into two phases including linear and nonlinear phases. The failure curve is nonlinear and related to the failure mechanism of transverse tension. The increasing trend of the cumulative counts can reflect the damage evolution process of transverse tension better. The transverse tensile fracture of 3D braided composites is not flush along the direction of fiber braiding and the failure modes are mainly matrix cracking, fiber deboning and few fiber fracture. The surface full-field information in the process of transverse tension reflects the damage evolution characteristics of the materials and provides basis for the structural health monitoring of 3D braided composites.

BUCKLING ANALYSIS OF VARIABLE STIFFNESS CYLINDRICAL SHELL AND OPTIMIZATION OF LAYING PATH

WU Shuang-hua, YIN Guan-sheng, CHEN Tong, ZHANG Bo

2020, 0(3): 37-43.

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In order to improve the buckling resistance of the cylindrical shell, two kinds of wire laying schemes were designed and the radial basis function metamodel was used to optimize the parameters in the two laying schemes. The calculation results of ABAQUS and ANSYS were compared to verify the reliability of ABAQUS modeling. The ABAQUS is used to analyze the buckling of the variable stiffness cylindrical shell under external pressure load, internal pressure load, combined load of external pressure and axial compression, combined load of internal pressure and axial compression. The radial basis function metamodel optimization algorithm is implemented by MATLAB to optimize the parameters of the wire laying scheme. The results show that compared with the laying method with linear variation of the laying angle, the non-linear variation of the laying angle is beneficial to improve the buckling resistance of the cylindrical shell under the combined load of the internal pressure and axial compression. For the cylindrical shell under the load of internal pressure and axial compression, the parameters m and n increased, which can improve the optimized buckling load. The buckling critical load and the laying path are approximate after optimization of the two wire laying schemes, and the accuracy of metamodel optimization is verified. It is feasible to optimize the parameters in the complex routing scheme by the radial basis function metamodel. The optimization results can provide a certain reference for the fiber-angled laying component.

PROGRESSIVE DAMAGE STUDY AND STRENGTH ANALYSIS OF CFRP BOLTED JOINTS

HUANG Yu-xiang, HUANG Xiang-yang, SONG Chun-sheng, SUN Cheng

2020, 0(3): 44-52.

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In order to obtain the dynamic damage process of CFRP bolted joints, the failure criterion and material degradation model of CFRP bolted joints under tension load are established by using progressive failure method. The finite element model of bolted joints is established in the explicit analysis module of Abaqus Explicit, and analyzed by using VUMAT subroutine. Five kinds of damage extension processes of CFRP single bolted joints under tension load are analyzed, and the influence of bolt-hole fit clearance on the strength of CFRP single bolted joints is analyzed. On this basis, the strength optimization scheme of CFRP multi-bolt connection structure is put forward. The results show that the finite element dynamic analysis based on progressive failure method can effectively simulate the damage propagation process of CFRP bolted joints. The strength of CFRP single bolted joints decreases with the increase of fit clearance, and the overall strength of CFRP multi-bolted joints is increased by 32.1% by setting appropriate fit clearance.

PREDICTING CFRP SHEAR CONTRIBUTION OF STRENGTHENED RC BOX BEAM BASED ON EXISTING EXPERIMENTAL RESULTS AND THEORETICAL MODELS

MA Sheng-qiang, ZHAO Rui, ZHANG Guang-tai, CAI Jing

2020, 0(3): 53-60.

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A great number of experimental and numerical studies focused on the FRP shear strengthening rectangular and T-section beams, and the several models for calculating FRP shear contribution have been proposed, which were introduced to the codes and guideline of different countries. The research on the FRP shear strengthening RC box beam, however, is rarely presented in the literature. In this study, therefore, CFRP shear contribution of strengthening RC box beam is predicted by existing experimental results and theoretical models. Five models from different codes about predicting FRP shear contribution have been reviewed and discussed. 181 FRP shear strengthening specimens with rectangular and T-sections collected from existing literature was calculated by the five models. Compared with experimental results, the predictions of FRP shear contribution have a certain scatter, but fib Bulletin 14 showed a relative accuracy in predicting the rectangular and T-section beams. Besides, based on the results from experiments of FRP strengthened RC box beam in shear, five models overestimated the FRP shear contribution because the effective strain of FRP sheets has been overestimated. Compared with other four models, the results predicted by fib Bulletin 14 are close to the experimental values, but still in unconservative side. Based on comparison of the effective strain of FRP calculated by fib Bulletin 14 and experimental values, a coefficient of 1.31, therefore, was also proposed, which divided the formula of the effective strain in the fib Bulletin 14 model according to the experimental effective strain in fiber. The model with the modified effective strain presented a rational prediction in CFRP shear contribution of strengthened RC box beams.

EFFECTS OF BASALT FIBER ON FRICTION AND WEAR PROPERTIES OF RESIN-BASED COMPOSITE MATERIALS

HE Huai-wen, SONG Xu-ding, FANG Shang-long

2020, 0(3): 61-65.

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In order to explore the application of basalt fiber in resin-based friction materials, composites with 0~20% (mass fraction) basalt fibers have been prepared by hot-pressing. Friction and wear properties, hardness and shear strength have been tested. The wear surface morphology has been observed by scanning electron microscopy (SEM), and its wear mechanism has been discussed. The results show that the basalt fiber can significantly improve the hardness and shear strength, reduce the wear rate and increase the friction coefficient and the heat fade temperature. The higher the hardness, the larger the friction coefficient, the higher the shear strength and hardness, and the smaller the wear rate. When the basalt fiber content is 15%, the wear rate is at least 0.23 cm³/(N·m). When the basalt fiber content is 20%, the friction coefficient is up to 0.45. The main wear mechanism of basalt fiber reinforced resin-based friction materials is abrasive wear.

THE ANALYSIS OF LOW FREQUENCY ACOUSTIC SCATTERING CHARACTERISTICS OF COMPOSITE STIFFENED CYLINDRICAL SHELLS

WANG Xiao-qiang

2020, 0(3): 66-69.

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The low frequency acoustic scattering characteristics of composite stiffened cylindrical shell and metal stiffened cylindrical shell are calculated and analyzed by using the finite element/infinite element method. In this paper, the acoustic scattering of stiffened cylindrical shells and non-stiffened cylindrical shells with different wave numbers are calculated, and two methods are used for stiffened cylindrical shells, including beam element modeling and shell element modeling. The results show that the modeling method of stiffener has some influence on the calculation accuracy, and it is even significant at some frequency points.

PREPARATION AND PROPERTIES OF CONTINUOUS FIBER REINFORCED POLYETHERSULFONE COMPOSITES

ZHOU Zhen-jun, ZHANG Ning, WANG Lin-jiang, CHENG Jing-qi

2020, 0(3): 70-74.

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Carbon fiber reinforced thermoplastic resin-based composite materials have been paid more and more attention in many fields such as aerospace and automotive industries due to their excellent performances such as light weight, high strength, short processing cycle and recyclable recycling. They have also become important developments in future composite additive manufacturing direction. In order to solve the problems of high energy consumption and difficult solvent removal in the preparation of composite prepreg by solution method, solvent volatilization causes environmental pollution and harm to human health, this paper uses high performance thermoplastic resin polyethersulfone (PES). As a substrate, the solution is removed by a solution dipping-phase transformation method at a normal temperature to remove the solvent at a normal temperature, and the method is energy-saving and environmentally friendly. Thermoplastic prepreg yarns with controlled resin content, good flexibility, and possibility for three-dimensional weaving and automatic placement molding are prepared by solution impregnation-phase transformation. It is thermoformed into an unidirectional tape sample, which is compared with the thermal properties and mechanical properties of common epoxy resins and their composite materials. It is found that the PES-based composite material has excellent heat resistance. Its thermal decomposition temperature (T_5%) is 576 ℃, the residual carbon ratio (N₂) at 800 ℃ is 90%, and the longitudinal tensile strength of the unidirectional belt can reach 1781 MPa. The tensile modulus is 60.17 GPa. Although it is slightly lower than the epoxy resin matrix composite of the same resin content, but the PES-based composite material is a high-performance thermoplastic composite material with great development potential.

FREQUENCY SELECTIVE DAMPING SANDWICH ABSORBING COMPOSITE

CHEN Xin-le, LIANG Sen, YAN Sheng-yu, ZHENG Chang-sheng

2020, 0(3): 75-79.

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An embedded co-cured damping and electromagnetic absorbing composite with multi-layer absorbing prepreg layer and absorbing damping layer was proposed, and the thickness of the absorbing wave prepreg layer and the absorbing damping layer was regularly adjusted to realize different frequency bands. The electromagnetic wave absorption was theoretically analyzed by Matlab using the Matlab. The specific thickness of the absorbing prepreg layer and the absorbing damping layer can be designed according to the specific requirements of the electromagnetic absorbing band. The electromagnetic absorbing test verified the selectivity of the electromagnetic absorbing frequency and the validity and rationality of the theoretical analysis method. Modal test and free decay test obtained the curves of modal parameters and damping loss factors with the thickness of absorbing prepreg. The experimental data show that the electromagnetic absorption frequency changes with the increase of the thickness of the absorbing prepreg layer of the specimen. The natural frequency of the mode increases, the modal damping ratio increases, and the damping loss factor increases.

EFFECT OF CONNECTORS ON NATURAL FREQUENCY IN CARBON FIBER COMPOSITE DRIVE SHAFT OF AUTOMOBILE

SUN Ze-yu, GAO Hong-ping, YU Xu-duo, TAO Lei

2020, 0(3): 80-83.

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In this study, the vibration characteristics of carbon fiber reinforced composite drive shafts with various metal connectors were studied using finite element analysis and experimental modal test. The results indicate that metal connectors with different weight and structures had remarkable influence on composite drive shaft′s modes and natural frequencies. Furthermore, the finite element analysis results keep record with the experimental values. In the optimum structural design of a composite drive shaft, the metal connectors are shown to play important roles in the vibration properties. The above results will provide a significant reference for design engineers.

RESEARCH ON X-RAY DIGITAL IMAGING DETECTION METHOD FOR LARGE VOLUME FIBER-WOUND GAS CYLINDER

HUANG Liang, JIN Ming-zhe, HE Qi, WANG Qian

2020, 0(3): 84-89.

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In order to verify the detection ability of digital ray for the main defects of large volume steel liner-wound gas cylinders, and to give quantitative data of detection ability, this paper is aimed at the breakage and scratch of fiber layer which may occur during the use and manufacture of gas cylinders. Defects such as pores and liner corrosion, cracks, etc., and artificial defects such as series of grooves and flat bottom holes were made on the fiber layer and the inner liner to simulate the above-mentioned natural defects. And the artificial sample images were taken through the optimized transillumination parameters. The test results show that the digital ray detection method can detect the longitudinal grooving with a depth of 0.25 mm on the fiber layer and the circumferential groove with a depth of 0.5 mm, and also detect the longitudinal and circumferential grooves of the 0.25 mm depth on the inner liner. This proves that digital ray detection can be used for the initial detection of large-volume steel liner-wrapped cylinders, which provides strong support for safe use.

RESEARCH ON TENSILE PROPERTIES OF T-STIFFENED COMPOSITE PANELS REINFORCED BY STITCHING

HUAN Hua-song, WEN Li-wei, XIAO Jun, FENG Qiao-qiao

2020, 0(3): 90-97.

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In order to improve the joint strength between the ribs and the skin in the T-reinforced wall panel of the composite material, stitching reinforcement technique is introduced. The self-developed curved needle sewing machine is used to prepare the suture T-joint sample by vacuum assisted resin infusion technique (VARI), and the tensile test is carried out to study the interface strengthening mechanism of the T-joint and the influence of stitch density and stitch fineness on the tensile properties of T-joint. The results showed that when stitching fineness is 1000 D and the stitching density is in the range of 0-10×10, the tensile limit load of the suture-reinforced T-joint increased with the increase of the stitching density. The ultimate load of stitched reinforced T-joints with stitch density of 10×10 is 38% higher than that of unstitched joints. The ultimate tensile load of stitched T-joints tends to decrease in the range of stitching density of 10×10-8×8. When the stitching density is 10×10, and the stitch fineness is in the range of 0-1000 D,the tensile load-carrying capacity of the T-joint increases with the thickening of the suture, and the tensile limit load of the T-joint decreases when the stitch fineness increases to 1500 D. The change in stitch density and seam fineness has no significant effect on the initial failure load of the T-joint.

STUDY ON COLLABORATIVE ANALYSIS OF SUSPENDED GLASS FIBER REINFORCED PLASTIC TUBE IN THERMAL POWER PLANT

GONG Jie-fu, PENG Xiong-zhi, ZHOU Quan, QI Hui

2020, 0(3): 98-103.

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At present, internal and external chimneys are mostly used for independent analysis in chimney design. In order to explore the design safety of different sections of suspended inner chimneys under the type of rod system unit and plate system unit respectively, and the differences between separate analysis and collaborative analysis, the finite element software analysis was used. It is found that under the combination of long-term and short-term loads, the GRP inner tube meets the bearing capacity requirements under the condition of meeting the minimum structural layer thickness, and the longitudinal stress of the plate and shell element is 4%~8% higher than that of the bar element. There is no significant difference in the maximum stress value of the FRP tube under 8 local wind loads in the plate and shell element model, which can be ignored. The maximum bending moment of chimney reinforced concrete external cylinder is 2%~8% different from that of the combined model.

PREPARATION AND PROPERTIES OF QUARTZ FIBER CLOTH/J-284PD CYANATE ESTER RESIN COMPOSITES

AO Liao-hui

2020, 0(3): 104-107.

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Quartz fiber cloth/J-284PD cyanate ester resin composites were prepared by hot-pressing tank forming method, and their mechanical properties,dielectric properties and moisture-heat resistance were verified. The results show that quartz fiber cloth/J-284PD cured at medium temperature composites materials have excellent mechanical, dielectric properties and moisture-heat resistance. Among them, the tensile strength is 630 MPa, the interlaminar shear strength is 58.8 MPa, the dielectric constant is 3.1, and the dielectric loss is 0.003. After 10 days of moisture-heat test, the maximum performance decline is only 10%.

PREPARATION OF SiO₂ AEROGEL-POLYSTYRENE COMPOSITE BY SUSPENSION POLYMERIZATION

YANG Zhen-yuan, WANG Xuan-jie, LI Rong-xun

2020, 0(3): 108-113.

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Silica aerogel-polystyrene composites were prepared by suspension polymerization. The effects of silica aerogel addition on the polymerization time, polymerization degree, molecular weight and distribution of the composites were studied. The influence on the properties such as T_g and high temperature stability of the composite was also investigated. The results show that with the increase of silica aerogel content, the polymerization time of the composite increases during polymerization, and the monomer conversion rate decreases. The GPC test shows that the number average molecular weight decreases and PDI increases with the addition of silica aerogel. In the mean time, the average particle size increased rapidly. The DSC and TG tests showed that the glass transition temperature and the initial decomposition temperature gradually increased, and the weight loss rate decreased.

STUDY ON MECHANICAL PROPERTIES OF BASALT TWO-DIMENSIONAL BRAIDED STRUCTURE COMPOSITES

YANG Chao-yue, XIAO Zhi-jie, GAO Yi-qiang

2020, 0(3): 114-119.

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Basalt fiber mesh material is a new type of fiber reinforced polymer composites, which is made of basalt braided rope as raw material. But the testing process of grid material performance is more complex. So the research on the mechanical properties of raw material can simplify the research process of grid material mechanical properties. The braided parallel fiber rope with different braided pitch rope such as 20 mm, 30 mm, 40 mm, 50 mm and 60 mm as rope core and basalt fiber roving as rope core were used as reinforcements. Composite materials with certain shape and properties were prepared by composite curing with epoxy resin CYD-128. The effect of rope core form on the mechanical properties such as tensile properties, bending properties and compression properties of the composites were tested. The results of one factor variance analysis show that the reinforcement rope core pitch has a significant effect on the tensile properties, bending properties and compression properties of the composites. The results of visual analysis show that in this experiment range, the fracture strength of the reinforcements with rope core pitch of 60 mm is the highest, which is 56% higher than the lowest value with rope core pitch of 20 mm. The tensile strength and compressive strength of the composite with reinforcement rope core pitch of 60 mm are the highest, which are 77% and 238% higher than the lowest value with reinforcement rope core pitch of 20 mm, and the bending strength of the composite with braided parallel fiber rope is the highest, which is 59% higher than the lowest value with reinforcement rope core pitch of 20 mm.

RESEARCH AND DEVELOPMENT STATUS OF FIBER REINFORCED COMPOSITE BOGIES

CHEN Guang-hao, LIANG Zhi-hong, ZHANG Zhi-fang

2020, 0(3): 120-130.

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With its excellent performance, composite materials have been rapidly developed from the field of aviation to the field of railway transportation to meet the requirements for rail transit vehicles to be light-weighted, low energy consuming and comfortable. This paper firstly introduced the domestic and international application situation of the composite materials in railway train, and then summarized the disadvantages of traditional metal bogies. In particular, the development and research progress on the composite bogies in Germany, Britain, France, Japan and South Korea were described in details. The paper pointed out the to-be-solved problems in the development of composite bogies for using in the rail transportation and offered suggestions of possible solution. This paper will provide some guidance and references for the research and development of fiber reinforced composite bogies in China.

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