COMPOSITES SCIENCE AND ENGINEERING

FIBER THICKNESS PREDICTION AND STRENGTH ANALYSIS OFCOMPOSITE HYDROGEN STORAGE VESSELS

WANG Hua-bi, CHENG Shuo, ZU Lei, ZHANG Qian

2020, 0(5): 5-11.

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Composite hydrogen storage vessels are widely used in aerospace and transportation as its high specific strength, specific stiffness and good corrosion resistance. This paper aims to provide a fast and accurate design method for composite hydrogen storage vessels through theoretical research and numerical simulation. Firstly, the composite winding layer is designed based on the grid theory, and then the cylinder contour is measured by 3D laser scanning technology, which verifies the accuracy of the prediction method of cubic spline dome thickness. At last, the finite element modeling of cylinder winding layer with variable thickness and angle was carried out by Abaqus finite element software. The important role of self-tightening in improving cylinder performance was analyzed, and the bursting pressure of cylinder was predicted by progressive damage. The results show that the cubic spline method can effectively predict the thickness distribution of the fiber. After auto-frettage, the Mises stress of liner decreased significantly under the working pressure, and the optimal auto-frettage pressure is obtained to be within 36.3 MPa~42.5 MPa. The failure mode of the vessel is predicted by progressive damage, and the final blasting pressure is 69.5 MPa, which meets the design requirements. The research results are of great significance to the design and manufacture of composite hydrogen storage vessels.

NUMERICAL SIMULATION OF FAILURE ANALYSIS OF CFRPLAMINATES UNDER COMPRESSION AFTER IMPACT

LI Yao-lei, TIE Ying, LI Cheng, SUN Zhen-hui

2020, 0(5): 12-18.

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The damage tolerance of composite laminates is a key factor in the design of composite structures. In order to solve the problem of low velocity impact damage and compression damage of composite (CFRP) laminates, based on continuous damage mechanics and cohesive element model, the low velocity impact and compression of impact simulation analysis of two kinds of composite laminates with different impact energy is carried out in ABAQUS. The intralaminar and interlaminar damage is studied, and the impact damage and compression failure behavior of composite laminates are analyzed. The effectiveness of the model is verified by comparing with the experimental results. The results show that the low velocity impact damage has an important effect on the residual compressive strength of composite laminates. The failure of the specimen begins in the impact damage area and gradually extends to the edge of the composite laminates. The compression force decreases rapidly and the laminates finally fails.

IN-PLANE MECHANICAL PROPERTIES OF EMBEDDED ANDCO-CURED STITCHED DAMPING COMPOSITE STRUCTURE

YAN Sheng-yu, LIANG Sen, CHEN Xin-le, WANG Ling

2020, 0(5): 19-24.

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In order to improve the in-plane mechanical properties of composites, an orthogonal symmetric embedded and co-cured stitched damping composite structure is presented. A numerical simulation model of the equivalent elastic parameters of the structure was established. The embedded and co-cured stitched damping composite specimens were manufactured by the medium temperature co-curing process of the autoclave. The tensile test of the universal testing machine verified the effectiveness of the numerical simulation method. The effective ANSYS finite element model is used to further analyze the variation of the in-plane equivalent elastic parameters E_x, E_y, G_xy and ν_xy with the stitch length, line spacing and damping layer thickness. It lays a foundation for the study of mechanical properties of embedded co-cured stitched damping composites.

THE COMBINED EFFECTS OF HYGROTHERMAL AND EXTERNAL LOAD ON THEMOISTURE ABSORPTION BEHAVIOR OF E-GLASS/EPOXY COMPOSITES

SUN Tong-sheng, YU Cun-gui, YANG Wen-chao, ZHONG Jian-lin

2020, 0(5): 25-31.

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This paper investigates the combined effects of hygrothermal and external tensile load on the moisture absorption behavior of E-glass/6509 epoxy composites. Governing equation for hygromechanical coupling diffusion is derived from the theory of irreversible thermodynamics. A new form of Gibbs free energy is introduced using temperature, moisture concentration and the matrix octahedral shear stress as independent state variables. Accelerated moisture absorption experiments in different hygrothermal environments were carried out with a self-made compression spring loading device, and response surface methodology (RSM) was used to establish a surrogate model for predicting the influence of environmental factors on the diffusion coefficient and equilibrium moisture content. The results show that moisture diffusion coefficient and equilibrium moisture absorption of composites increase with the increase of matrix octahedral shear stress. The moisture absorption of composites can be accelerated by increasing temperature, and the equilibrium moisture content can be increased by increasing the relative humidity. The surrogate model obtained by the response surface method can accurately predict the moisture absorption behavior of glass fiber/epoxy composites under the effect of hygromechanical coupling.

STUDY ON THE CALCULATION METHOD OF PRELOAD FOR COMPOSITE PRE-TIGHTENEDTOOTH CONNECTIONS BASED ON EXTRUSION METHOD

ZUO Yang, LI Fei, ZHAO Qi-lin, GAO Jian-gang

2020, 0(5): 32-39.

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In the composite pre-tightened tooth connections, the pre-tightening force determines the ultimate bearing capacity of the joint. When the pre-tightening force is applied by external extrusion, the size of external extrusion determines the pre-tightening force applied to the joint. In this paper, the relationship between external extrusion and pre-tightening force is studied by theory, finite element and experiment. Firstly, steel and aluminum alloy are simplified as ideal elastoplastic materials, and pultrusion composites are simplified as transversely isotropic materials. Then, through the thick wall cylinder theory, the theoretical formula for calculating the radial compressive stress of the interface under different extrusion variable is obtained, which is verified by finite element method and experiment. Finally, the parameters are studied on this basis. The results show that: (1) The theoretical solution is in good agreement with the finite element solution and the experimental value, which proves the correctness of the theoretical formula. (2) When only the wall thickness is changed, the radial compressive stress of the interface increases linearly with the increase of the wall thickness of aluminum alloy inner casing, while the external steel casing wall thickness has little influence on it. (3) When the material of inner sleeve is changed from aluminum alloy to steel and other conditions remain unchanged, the radial compressive stress of the interface will be significantly increased.

STRUCTURE DESIGN OF CARBON FIBER GRID SANDWICH REFLECTOR WITH HIGHSTABILITY AND OPTIMIZATION OF THERMAL DEFORMATION

ZHANG Wei-bo, ZHANG Qi, XU Hong-tao, JU Bo-wen

2020, 0(5): 40-46.

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To control thermal deformation of reflecting surface of satellite-borne reflector during orbit operation, a high stable carbon fiber grid sandwich structure with simple manufacturing process was designed for a paraboloid reflector with a diameter of 1.2 m. A numerical simulation method was established to predict thermal deformation of reflecting surface. On this basis, influence of different structural parameters of grid core on thermal deformation of reflecting surface was studied, and optimization of these structural parameters was performed with root mean square (RMS) of thermal deformation as indicator. And then, the reflector with optimized structure was manufactured and thermal deformation of reflecting surface was measured at low temperature using digital close-range photogrammetry to verify the validity of the numerical simulation method. At last, the influence of resin film for surface restoration on thermal deformation of reflecting surface was further studied. The results demonstrate that the RMS of thermal deformation of reflecting surface after structural optimization is 4.03 μm under uniform temperature field of -80 ℃~25 ℃, which meets the application requirement of submillimeter wave antenna. And RMS of thermal deformation of reflecting surface increases linearly with the increase of thickness and linear expansion coefficient of resin film for surface restoration. Therefore, thickness of the resin film must be strictly controlled and resin with low linear expansion coefficient should be selected during the surface restoration process.

EXPERIMENTAL STUDY ON CREEPAGE DAMAGE OF GFRPUNDER SIMULATE LIGHTNING CURRENT

YANG Chun-hao, ZHAO Yang, XIAO Yao, XING Hong-yan

2020, 0(5): 47-52.

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In order to study the damage characteristics of GFRP under lightning strike, the lightning strike simulation experiment was carried out in the surface flashover mode. The damage morphology was observed by visual observation, high-definition scanning, image processing analysis and electron microscopy. The results indicate that the thickness of the test plate and the change of the creeping direction have obvious influence on the damage of the resin. The damage area of the test material is positively correlated with the current amplitude and the integral of the action, and negatively correlated with the thickness of the sample plate. Surface flashover mainly causes thermal decomposition damage of resin on the discharge path, where the fiber damage is not obvious, and the interface is layered by thermal decomposition of the resin.

EFFECT OF WASHER SIZE ON BEARING STRENGTH OF SINGLE-LAPBOLT JOINT IN CARBON FIBER REINFORCED COMPOSITES

ZHANG Xin-yi, KONG Hai-juan, HU Zhi-feng, SUN Ze-yu

2020, 0(5): 53-62.

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An experimental study of the diameter size of washer on the bearing strength and failure of carbon fiber reinforced composites single-lap bolt joints were investigated. It was found that the bearing strength of single lap bolt joint was improved by the increasing of diameter of the washer. When the diameter of the washer is gradually increased from 11.8 mm to 13.8 mm, 15.8 mm, 17.8 mm, the bearing strength is gradually increased by 5.76%, 5.87%, 2.4% accordingly. However, the experimental results show that when the diameter of the washer increases to a certain extent, the effect of strengthening the bearing strength is weakened. But there was no effect on the failure mode, and the failure mode is still the extrusion failure mode. A 3D model of carbon fiber reinforced composite laminates with bolt joint is created by using the software Abaqus. The 3D Hashin failure criteria with tensile delamination damage and compression delamination damage and the improved material stiffness degradation model of Tan and Tserpes were introduced. The simulated model captures the experimentally obtained results with error less than 10%, and predicts the failure modes successfully.

STUDY ON VIBRATION PROPERTIES OF CARBON FIBER REINFORCEDCOMPOSITE TUBES WITH DIFFERENT INNER DIAMETERS

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

2020, 0(5): 63-68.

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In this study, the vibration characteristics of carbon fiber reinforced composite tubes with various inner diameters were studied using finite element analysis and experimental modal test. The results indicated that natural frequency of composite tubes increased with the increases in the inner diameter. The high accordance of the simulated and measured results indicated the reliability of the simulation. Under the free state, the first vibration of composite tubes with different inner diameters occurred bending vibration. During the vibration, position 1/4 and 3/4 of the tube did not deform but the middle and both ends deformed greatly. With the increase of the inner diameter of the composite tubes, the vibration attenuation coefficient decreased gradually. The change of damping property caused by the inner diameter of the shaft tube has a great influence on the vibration attenuation of the composite tube under free state, but the damping change has little influence on the natural frequency of the shaft tubein the free state.

EFFECT OF DIFFERENT NON-WOVEN FABRICS ON MECHANICAL PROPERTIESOF GLASS FIBER/VINYL ESTER COMPOSITES

MA Peng, LI Jin, KANG Shao-fu, ZHOU Shao-xiong

2020, 0(5): 69-73.

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In order to improve the interlaminar properties of glass fiber/vinyl ester (GF/VE) composites, GF/VE composites with polyamide (PA), copolyester (PEs), polyurethane (TPU) and vinyl acetate (EVA) nonwoven fabrics were prepared by VARI process. The tensile, flexural and mode Ⅰ interlaminar fracture toughness of the composites were studied. The results show that the mode Ⅰ interlaminar fracture toughness of GF/VE composites increases by 142%, 103%, 46% and 45%, respectively, by adding PEs, TPU, PA and EVA nonwoven fabrics. The tensile strength of GF/VE composites increased by 6.43% by adding TPU non-woven fabrics, while the others decreased by 2.93%, 3.72% and 28.67%, respectively. After adding different non-woven fabrics, bending strength decreased by 13%, 14%, 25% and 60%, respectively. The strengthening and toughening effects of co-polyester and polyurethane nonwoven fabrics on GF/VE composites are better than that of polyamide materials.

FEASIBILITY ANALYSIS OF DOUBLE-ROW SMALL DIAMETER PIPEREPLACING SINGLE-HOLE LARGE DIAMETER CULVERT

WANG Qing-zhou, SUN Yan-wen, ZHANG Wen-yu, ZHANG Yu-ning

2020, 0(5): 74-79.

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In order to solve the problem that the application of large diameter FRP pipe is limited by subgrade elevation and top filling height, the mechanical properties, culvert cost and engineering cost of small diameter double row FRP pipe culvert and large diameter single row FRP pipe culvert are compared and analyzed, and the replacement of small diameter double row pipe is demonstrated. The results show that: under the same subgrade design elevation, small diameter double-row pipe culverts can obtain more sufficient soil cover height, which significantly weakens the stress effect of external loads on the culvert. The alternative scheme can ensure the service of the pipeline under low stress state, which is beneficial to prolong the service life of the pipeline. Under the same working conditions, the stress values of single-row pipe and double-row pipe meet the requirements of their compressive strength and tensile strength, and the culvert with small diameter and double-row pipe has better safety reserve. The production cost and engineering cost of the culvert with small diameter and double-row pipe can be saved by 1172.39 yuan per meter, and the economic benefit can be achieved significant.

STUDY ON DEFORMATION CORRECTING TECHNIQUE OF SADDLE-SHAPEDCARBON FIBER COMPOSITE COMPONENT

LIU Bao-ming

2020, 0(5): 80-83.

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Aiming at the deformation of saddle-shaped carbon fiber composite component, the deformation law was obtained by experimental method. Taking the section angle as the parameter, the variation law equation of the deformation parameters was established to predict the solidification deformation of the components. By using CATIA/CAA secondary development technology, the correction software of saddle shape was developed, and the manufacturing error of parts was reduced through actual correction of saddle shape, which proved that this method can effectively reduce deformation and improve the precision of parts.

A MUTI-SCALE CONSTITUTIVE MODEL AND ITS APPLICATIONSFOR GLASS FIBER COMPOSITES

CHEN You-song, HAN Hong-yang, HU Hong-cheng, ZHANG Dao-tong

2020, 0(5): 84-89.

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Constitutive Model plays an important role in the design and analysis of composite structure, and one of the most widely used strength criteria is the Tsai-Wu criterion. In the Tsai-Wu criterion, the cross-term parameters are usually determined by double-axis test. Empirical values are often used to replace cross-term parameters, which affects the accuracy of the model. Based on the glass fiber reinforced composite material, this study establishes a multi-scale model. In order to determine the cross-term parameters, simulation is performed under the double-axis load condition. On this basis, a multi-scale model of glass fiber composite material is established, and the accuracy of the model is verified by three-point bending simulation and experiment. The results show that the calculation error is less than 5%. Finally, the established model is applied to the design and analysis of a glass fiber composite leaf spring, and the result meets the design requirements.

LOW COST MANUFACTURING TECHNOLOGY OF RADOME

ZHU Yong-ming, YANG Chun-xia, WU Dong

2020, 0(5): 90-94.

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With the development of composite materials technology, the cost reduction of the radome raw materials and the low cost of the molding process are the direction for the design and production of the radome. In this paper, the raw materials of sandwich radome are optimized and tested. The sandwich radome was fabricated by solvent-free wet prepreg and vacuum bag pressing method. Through the electrical performance and environmental adaptabilitiy test, the radome meets the requirements of product design and use. The main material cost of the low-pressure molded sandwich radome for wet prepreg is greatly reduced. The cost of the radome fabricated by this way is more than 50% lower than that of traditional dry prepreg/PMI radome, which is more than 70% lower than that of the honeycomb sandwich radome. It can be widely used in the production of radomes on the ground radars.

RESEARCH ON THE INFLUENCE OF SECONDARY BONDING VERIFICATION ACCURACYOF COMPLEX HONEYCOMB SANDWICH STRUCTURE

YUAN Chao, LI Shao-liang, CHEN Jing

2020, 0(5): 95-99.

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In view of the secondary bonding process of complex honeycomb sandwich structure, the factors affecting the calibration accuracy are studied by using different verification pressure and verification film combination mode. The results show that the effect of external pressure on the verification accuracy of complex honeycomb sandwich structure is very small at low pressure. The combination method of verification film has a great influence on the verification accuracy. The results of different combination verification films for different areas is better than that of single verification film for different areas. According to the results of the combined verification experiment, the model of verification films selection for the combined verification is established and verified.

THE EFFECTS OF WIND TURBINE BLADE TRAILING EDGE MODELING WAY ON BUCKLING

ZHAO Chun-ni, LIU Qing, CHEN Wen-guang, LI Jun-xiang

2020, 0(5): 100-104.

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Buckling of trailing edge is one of the main failure modes of wind turbine blades. In this paper, the finite element method is used to study the difference of buckling in different modeling methods, including, the slope of trailing edge core, trailing edge UD staggered layer, and adhesive modeling method. The results indicate that the trailing edge adhesive may be defined as a solid or shell element (equivalent to a small web). The slope of trailing edge core can be simulated by no less than 3 steps, and the trailing edge UD of each staggered layer can be appropriately simplified.

THE PROCESS OF THERMOPLASTIC PULTRUSION USING GLASSFIBER/POLYPROPYLENE COMMINGLED YARNS

JING Rong, ZHANG Rui-tao, MENG Yu-chen, WANG Yan-hui

2020, 0(5): 105-111.

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The impregnating process in thermoplastic pultrusion using glass/polypropylene (GF/PP) commingled yarns was studied. Based on Darcy-Law, variation of pressure drop, transverse permeability and viscosity were investigated under different geometrical/process/material parameter. The pultruded samples were obtained on the lab-designed thermoplastic pultrusion line under different temperature/die geometry. The porosity was calculated, and flexural strength was measured to verify the impregnation process analysis. The study showed that the existence of proper tense helped increasing impregnating uniformity. And 200 ℃~220 ℃ is an optimal mold temperature in melting section for resin flow in impregnation. A conical die wall geometry in melting section is essential for transverse impregnation process.

FRONTAL CURING OF EPOXY RESIN AND ITS COMPOSITE BY UV RADIATION

ZHAO Pei-zhong, TAN Xiao-ming, DAI Jing-tao

2020, 0(5): 112-116.

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UV-induced frontal curing behaviors of epoxy resin systems including not only the photoinitiator but also the thermal initiator were studied. Increase of the content of thermal initiator can increase frontal rate obviously. The frontal curing of CEP/PBMA semi-IPN systems were also studied. Compared with pure epoxy resin, the frontal rate of semi-IPN is lower. Without the thermal initiator, the front propagating of the semi-IPN can not be sustained. TG and DSC results show that the beginning degradation temperature and glass transition temperature decrease with the increase of the BMA weight percent. Carbon fiber fabric reinforced composite materials based on epoxy resin systems were prepared successfully using UV radiation. The epoxy resin matrixes include pure epoxy and EP/PBMA semi-IPN systems. According to the tensile testing results, with the increase of BMA weight percent, the tensile strength of composite decreases gradually.

EFFECT OF MOLDING METHOD AND TECHNOLOGICAL PARAMETERS ONMECHANICAL PROPERTIES OF GF/PP COMMINGLED YARN

ZHAO Yu, ZHANG Yong-bing, ZHANG Xing-gang, WANG Yan-hui

2020, 0(5): 117-122.

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The glass fiber/polypropylene (GF/PP) commingled yarn was laminated by compression molding under various process parameters. The effects of molding temperature, molding pressure and dwell time on the mechanical properties of GF/PP composites were investigated by orthogonal test. Tensile strength, flexural strength and impact strength were used to evaluate the mechanical properties of GF/PP composite laminates. The results show that comprehensive mechanical properties could be improved by preloading before molding compared to the direct molding compression. The optimum process parameters of laminates made of GF/PP continuous composite fiber fabric was found, for which the molding temperature was 210 ℃, the pressure applied on the laminate was 10 MPa, and the holding time was set as 20 min.

OVERVIEW OF THE APPLICATION OF ADVANCED COMPOSITE MATERIALS ON AIRCRAFTAND THE DEVELOPMENT OF ITS MANUFACTURING TECHNOLOGY

NING Li, YANG Shao-chang, LENG Yue, Ren Xue-ming

2020, 0(5): 123-128.

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This paper summarizes the development plans which promoting the applications of composite materials in aircraft in Europe and the United States for the last 40 years, as well as the composite materials used in military and civilian aircraft at different times. In the meantime, this paper comparatively analyzes the development of domestic aviation composite materials and the composite materials used in domestic military and civilian aircraft in different periods, and introduces the automated manufacturing technology of composite materials and the low-cost manufacturing technology of liquid composite moulding. Finally, the opportunities and challenges in domestic advanced composites′ manufacturing field was proposed.

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