COMPOSITES SCIENCE AND ENGINEERING

THE STABILITY OF FGM CIRCULAR PLATES SUBJECTED TO FOLLOWER FORCE

LI Qing-lu, LUAN Wei-di, LI Shi-rong

2016, 0(10): 5-10.

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The stability of the functionally graded material circular plate made of ceramic and metal subjected to follower force were investigated. It is assumed that the properties of the functionally graded material vary continuously only with the thickness of the plate and their variation has a simple power law distribution with the volume fraction of the constituents. The governing equations are derived, and then the nonlinear governing equations with two kind boundary conditions are numerically solved by shooting method, respectively. The effects of power index and boundary condition on the behavior of buckling and bending were discussed. The numerical results indicated that homogenous circular plate occurred in the traditional sense of the buckling under two kinds of boundary conditions, and FGM circular plate under the follower load will be buckling when the gradient index p<1, and plate only bending when p>1. Results show that the gradient properties of the materials and the boundary conditions have important effects on the bending and buckling behavior.

EXPERIMENTAL STUDY ON BULKHEAD′S DIRECTIONAL EFFECT OF REINFORCED FOAM CORE COMPOSITES SANDWICH STRUCTURES

SUN Yun-lou, QI Yu-jun, WANG Hui

2016, 0(10): 11-14.

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In order to analyze the directional influences on failure mode and mechanical behavior of diaphragm reinforced foam core sandwich beams caused by bulkhead′s arrangement direction, three point bending tests were conducted on 3 sandwich beams, which were made through vacuum infusion process including unidirectional reinforcement and bidirectional enhancements. The results show that the failure modes of sandwich beams reinforced by transversal, longitudinal and bidirectional bulkhead were top panel′s bending broken, lateral panel′s local buckling and top panel′s local shearing failure, respectively. The ductility of beams under lateral load was improved due to the reasons that inclined cracks propagation was prevented by transversal bulkhead. Compared with the unreinforced sandwich, the capacity and elastics modulus of sandwich beams strengthened by longitudinal bulkheads were increased by 1.02 and 5.65 times, respectively, while the ductility changes into 1.23 multiples of the original. Mechanical behaviors of specimens that were reinforced by longitudinal and bidirectional bulkhead are similar, and their carrying capacity and elastic modulus were superior to those reinforced by transversal bulkheads.

DESIGN AND SIMULATION FOR WINDING PATTERN OF DRY FIBER REINFORCED RUBBER EXPANSION JOINT

YOU Bo, WANG Yan, XU Jia-zhong, ZHANG Xi

2016, 0(10): 15-19.

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Rubber expansion joint, as a kind of free telescopic elastic compensatory components, has good corrosion resistance, high impact strength and excellent damping noise reduction features compared with metal ones that extensively used in home at present. Expansion joints are mainly used in rigid piping systems. Conventional production using prefabricated fiber plies manual or semi-automatic technologies, do not allow optimal orientation of the reinforcement material. Without controlling the orientation of the reinforcement, it is not possible to control the shape while pressurized. Using dry fiber reinforced rubber expansion joints can fully play the role of fiber and is able to achieve automatic winding, improving efficiency, quality, and product consistency. This article analyzed the principle of dry fiber winding. Then, a set of equations can be obtained that describe these geodesic isotensoid fiber path shapes by combining netting theory and the membrane theory and establish the model of single bellow isotensoid expansion joint in terms of equations. Next, this article determines geodesic paths of model surface by numerical techniques and finally carries out the simulation according to the designed winding pattern. From simulation results, we can see stability and no obvious phenomenon of overhead. This design method of dry rubber expansion joint filament winding plays a very important role for the actual production in the future.

NUMERICAL SIMULATION ON TEMPERATURE FIELD FOR PREPOLYMERIZATION PROCESS OF PMI FOAM CORE MATERIAL

XUE Peng, LI Wen-xiao, ZHOU Jing-long

2016, 0(10): 20-25.

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Inappropriate temperature control may bring about implosion when polymethacrylimide (PMI) foam is prepared by two-step method. In this paper, we measured the critical temperature of the implosion and the changing trend of the polymerization system temperature in the process of preparing PMI with methylacrylic acid (MAA) and methacrylonitrile (MAN). Then the effects of ambient temperature and the size of the prepolymer on the temperature field of the polymerization system were studied by simulating the temperature distribution of the polymerization system in ABAQUS.

STUDY ON WOUND LAYER RESIN CRACKING FACTORS FOR CNG-2 TYPE CYLINDERS

LIU Lin-Lin, XIANG Zhong, HU Xu-Dong, LU Hai-Liang

2016, 0(10): 26-31.

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Aiming at improving compressed nature gas (CNG) cylinders wound layer resin anti-crack characteristic, a multi-scale modeling method is proposed to investigate the resin cracking mechanism. In the simulation model, the influences of gel content of winding layer and fiber diameter was discussed by micro-mechanics approach. Simulation results indicate that resin cracking degree is reduced as the gel content increases, and the resin cracking degree reaches the minimum point while the gel content was set to 34%. Then the influence of fiber diameter on the resin crack was discussed using a multi-scale model by setting gel content to 34%, and the simulation results indicate that fiber diameter almost has no effect on the cracking of the resin. Finally, the validaty of the multi-scale model is verified by experimental results. Since the gel content can be adjusted by precisely control the winding tensions, the study can be adopted to reduce the degree of resin cracking and provide the theoretical reference for improving the production of CNG-2 cylinders.

THREE-DIMENSIONAL NUMERICAL SIMULATION ON THE FIBER LENGTH DISTRIBUTION IN INJECTION MOLDING OF LONG FIBER REINFORCED POLYMER

JIANG Qing-song,LIU He-sheng

2016, 0(10): 32-37.

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Based on Phelps-Tucker fiber breakage model, a center-gated disk was used for a three-dimensional numerical simulation during flow in injection molding of long fiber reinforced polymer by using Moldflow. The effects of flow rate, melt temperature, mold temperature and holding pressure on fiber length distribution were investigated, and the mechanisms were discussed. The results show that the longest and shortest fibers coexist near the gate, and the fiber length near the wall is larger than that of central layer. With flow rate, mold temperature and holding pressure increasing, the fiber length increases correspondingly. With the increase of melting temperature, the fiber length decrease first and then increase. Holding pressure near the wall has minimal impact on fiber length. These results from numerical simulation agree well with the corresponding references.

FINITE ELEMENT ANALYSIS OF EFFECT OF GEOMETRY ON TETHER JOINT STRENGTH WITH ORTHOGONAL METHOD

LI Xin, ZHANG Jin-kui, WANG Xue-ming

2016, 0(10): 38-41.

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A new tether joint structure is introduced, which utilizes finite element method (FEM) and orthogonal design method widely used in experiments to figure out how the three geometric factors (bottom circle diameter, glue height, and taper angle) exert influences on the bonding joint strength under different level conditions. The results show that all the three factors have significant effects on the bonding joint stress, of which the influence of glue height is the largest, bottom circle diameter less and taper angle the least.

THE INFLUENCE OF TEMPERATURE ON THE THERMODYNAMICS PROPERTIES OF COMPOSITES

GAO Hong-cheng, HUANG Qi-zhong, MA Shuai, HU Zhao-hui

2016, 0(10): 42-49.

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As the temperature of severing environment variating severely, there would be a great alteration in the thermodynamics properties of composites. Due to the great difference of thermal expansion coefficient between internal fiber and resin in the composites, the resin performance is more sensitive to temperature environment. In this paper, based on the Maxwell constitutive model, the relationship between resin constitutive and temperature is studied. Assuming that the fiber performance does not vary with temperature, according to the mesoscopic composite theory, a hexagon representative volume element is employed, and the finite element method (FEM) is adopted to establish the thermodynamics constitutive model of composites under temperature. The influence of fiber arrangement and fiber content on the composites thermodynamics constitutive is discussed, respectively. The process would be applied for a multi-scale solution for composite under thermodynamics coupling loads.

STUDY ON THE HOT DIAPHRAGM FORMING OF CARBON FIBER COMPOSITE WITH BEAM AND RIB PARTS

WANG Dong-dong, XU Heng-yuan, GONG Zhi-hong, LI Cheng-long

2016, 0(10): 50-55.

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The 3234/T700 carbon fiber composite beam/rib parts was prepared by a home-made hot diaphragm forming equipment, and cured into the autoclave. The effect of forming temperature, forming time and thickness on the forming process was investigated by the surface quality, mechanical properties, thickness and internal defects of the cured parts. The result shows that the quality of the parts can be improved by increasing the forming temperature and forming time appropriately.

THE DEFORMATION OF FRPM PIPE BURIED IN HIGHWAY UNDER VEHICLE LOAD

ZHANG Ji-yuan, WEI Lian-yu, ZHANG Guo-pan, CHEN Zhao-nan

2016, 0(10): 56-59.

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In order to study the axial deformation of FRPM pipe buried in highway under unconventional vehicle load, an outdoor static test was designed with the method of hierarchical load. Then, through the comparison of the result measured by ABAQUS and outdoor test, the model that could meet the actual working conditions was established. Finally, the axial deformation under every filling height was calculated. This work can provide the detailed and reliable theoretical basis for FRPM pipe applied in highway.

DESIGN OF CONTROL SYSTEM FOR FILAMENT THREADING MECHANISM BASED ON PLC

TIAN Hui-fang, XUE Fei

2016, 0(10): 60-64.

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For the automation needs of filament threading and cutting in filament winding process, the PLC has been proposed as the core of filament threading control system. Meanwhile, the basic structure and work principles of filament threading mechanism is portrayed in detail, coupled with analyzing its working flow and allocating the I/O points. In addition, the overall design of software for control system was realized. And for the automatic mode of operation, pneumatic control, free port communication and stepper motor control were discussed in deep. Initialization of communication port and design of stepper motor speed curve were completed, and the corresponding sample program were listed.

ANALYSIS OF DAMAGE CHARACTERISTICS OF CARBON WOVEN FABRIC/EPOXY LAMINATES SUBJECTED TO SIMULATED LIGHTNING STRIKE

HUANG Lai,LI Yi-chao, CHE Hong-wei, ZHOU Ting

2016, 0(10): 65-69.

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This paper experimentally investigates the damage characteristics of two stacking sequenced carbon woven fabric/epoxy laminates subjected to three different levels of simulated lightning strike. The mechanical properties of post-lightning specimens are then studied. Observations show that three types of lightning strike damage have been formed. With the increase of strike intensity, different behaviors have been shown for these three damage forms. Meanwhile, stacking sequence has significant influence on the area of internal delamination. SEM shows that the resin/fiber interfacial bonding is severely damaged by a thermal-mechanical effect due to lightning strike infliction. For both of the two stacking sequenced specimens, the residual modulus and strength decrease with the increase number of lightning strike. However, failure mechanics are quite different for the two kinds.

MEASUREMENT AND ANALYSIS FOR THE COMPLEX PERMITTIVITY OF DIELECTRIC MATERIALS AT HIGH TEMPERATURE

XU Yin-fang, ZHANG Li-song, ZHANG Yan, LIANG Huan

2016, 0(10): 70-74.

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Complex permittivity measurements at high temperature by short waveguide method were obtained, and the measurement and analysis results of some typical dielectric materials from room temperature to 1600 ℃ were given. The results show that, before 1000 ℃, the dielectric constant and the loss angle tangent of composite material will decrease with the increase of temperature, due to the presence of the surface water adsorbed and in vivo physical water. When the temperature is rising to 1000 ℃, dielectric constant and loss angle tangent decreases to minimum, which shows that composite materials in the absorbed water volatile completely. When the temperature is above 1000 ℃, the dielectric constant and loss angle tangent are greatly increased because of the trace impurities introduced in the preparation of composite materials, which will ionize and generate particle conductance with increasing temperature. The measurement methodology and considerations can be used in the study of hypersonic electromagnetic windows.

AN EXPERIMENTAL STUDY ON BOLTED CONNECTION STRENGTH OF MT700 CARBON FIBER COMPOSITES

LI Gui-yang, LI Jian-fang, ZHANG Ya-ting, HUANG Zhi-bin

2016, 0(10): 75-79.

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The connection strength, load-shift behavior and failure mode of single-bolted joint specimens for MT700 and T700S carbon fiber composites were investigated via static tensile-strength experiments. The MT700/603 laminates exhibit simultaneously superior load-carrying ability and structural stability. Meanwhile, their connection failure strengths for M5 and M6 single-bolted joint have increased by 12% and 10% compared to T700S/603 laminates, respectively. Moreover, the adhesive-bolted joint pattern of MT700/603 laminates could effectively improve their integral connection strength and structural safety margin. After adhesive layer failure, the residual strength coefficients for M5 and M6 adhesive-bolted joint were also as high as 65% and 88%, respectively.

EXPERIMENTAL INVESTIGATION ON FATIGUE PROPERTIES OF CFRP MARINE PROPELLER BLADE

WU Jian, CAO Yao-chu, LI Hong-yun, WANG Wei-bo

2016, 0(10): 80-83.

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The blade of marine all-direction propeller was prepared from CFRP, which was designed and manufactured based on structure design of whole machine. The maximum design load is equivalent from pressure on blade surface under limited conditions by CFD method. Finally, fatigue test and residual strength test are completed on the specially designed device. The results show that the propeller blades don′t have any visible damage after fatigue test and the residual strength is far above limited strength. The structure design and manufacturing process of composite blade meet marine propeller′s requirements.

STUDY ON THE RHEOLOGICAL BEHAVIOR OF JOINT THICKENING ON BULK MOLDING COMPUND

XU Xiao-qiang, ZHOU Quan, NI Li-zhong, TONG Hua

2016, 0(10): 84-87.

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Molded rheological property is a quite important process parameter for unsaturated polyester bulk molding compound (BMC) in the industrial process of pressing. Due to the poor performance of rheological molding process in traditional manufacturing process of BMC, the molding requires larger molding pressure and longer molding time. As a result, it not only increases the possibility of die loss, but also reduces the productivity of the plant. This article discusses systematically the influence of rheological behavior of chemical thickener Ca(OH)₂ in the molding process of BMC. On this basis, the crystalline resin was used to joint thicken BMC with Ca(OH)₂. Through tablet flow properties and spiral flow analysis of thickened BMC, the results show that the crystalline resin and Ca(OH)₂ as a complex thickening system will not affect the curing behavior of BMC. In fact, it can improve the molding flow properties of BMC and make the BMC be able to be molded under the low pressure.

REVIEW ON UV CURING RESIN AND COMPOSITES

ZHU Pu, ZHANG Jian-wei, JIANG Da-zhi

2016, 0(10): 88-94.

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Fiber reinforced polymer (FRP) composites are usually through thermal treatment cured. However, the long molding cycle of thermocuring process hinders the rapid production, which is critical for the automobile industry. The ultraviolet (UV) curing process is both highly efficient and environment-friendly, therefore meeting the demands of the mass production of FRP for the automobile manufacturing. In this article, the key points of UV curing for both resins and composites are reviewed. The research progress on the curing kinetics, resin compounding, molding process, as well as the composites fabrication and repair technologies are introduced. At last, a brief prospect on the development trend of the UV-curing resin and composites is proposed.

COMPOSITE FUEL TANKS FOR THE GLOBAL PRECIPITATION MEASUREMENT SATELLITE

WANG Li, Ding Xin-Jing

2016, 0(10): 95-97.

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In this paper, composite fuel tank for the Global Precipitation Measurement Satellite was introduced, which could be demised during the reentry and decrease the space trash and the damage to human beings and the environment. The design requirements were illustrated from the pressure, operating temperature and light weight, etc. And the fiber-wound tank and prepreg layup skirts and their joints were discussed from the components including PMD, liners and pressure cylinder. Finally, it was thought that the tank has the bright future in satellite application and the further significance in space environment protection.

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