COMPOSITES SCIENCE AND ENGINEERING

STUDY ON THE STRUCTURE AND MECHANICAL PROPERTY OF 3D CURVEDSHALLOW-CROSSING LINKING COMPOSITES

FENG Gu-yu, CAO Hai-jian, QIAN Kun, SUN Jie

2016, 0(2): 5-9.

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Two different structure of 3D curved shallow-crossing linking woven fabric with 3 and 6 layers was prepared using glass fiber with the linear density of 2400tex as raw material on a 3D loom modeled SGA598. Two piece of 3 layers 3D curved shallow-crossing linking woven fabric were stacked to keep the same layers with the other one. The 3D curved shallow-crossing linking weaving composite applying in armored car interior was successfully prepared by hand composite modeling curved shallow-crossing linking woven fabric and resin system which was composed of epoxy resin and polyether amine in a mass ratio of 3∶1, in the mass ratio of 1∶1. Universal material testing machine modeled Instron 3385H was employed to characterize the stretch and bending property of the composite. Test procedure and destroy section were observed in order to compare composites mechanical property. Result shows that the composites expressed brittle failure when it bear stretch and bending load; 6 layers 3D curved shallow-crossing linking weaving composite has better mechanical property than 3 layers 3D curved shallow-crossing linking weaving composite; and 6 layers 3D weaving composite is protected better and the service life is extended.

RESEARCH ON PROCESS AND MECHANICAL PROPERTIES OF EPOXY RESIN COMPOSITEREPAIRED BY SCANNING MICROWAVE IRRADIATION

YOU Yan-yu, LI Yong, HUAN Da-jun, LIU Zheng-jie

2016, 0(2): 10-17.

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Microwave heating has a lot of advantages compared with the traditional heating method, such as heating fast, heating uniformly and so on. It is promising to apply microwave curing technology to the repair of composite materials. In this paper, composite laminated plates with prefabricated defects was repaired by microwave scanning equipment and the microwave scanning repair process as well as the mechanical properties of samples after repair was studied. The results show that the curing process with an input DC current of 300 mA possess high curing efficiency. At the same time, the curing product is of good mechanical properties, so we select this process as microwave scanning repair process eventually. When the repairing sample adding no covering ply, the tensile properties retention rate is relatively high, while the bending properties retention rate is relatively low. Tensile strength and modulus retention rate are 89% and 92.7%, respectively. Bending strength retention rate loading on bending surface and back surface are 74.9% and 77.5%, respectively. When the repairing sample adding covering plies, the tensile and bending properties of the sample are improved, and the tensile strength and modulus remain rate increased to 98.7% and 95.4%, respectively. The bending strength loading on bending surface and back are increased to 96% and 94.4%, respectively. Compared with the thermal curing repair, microwave scanning repair can save about 70% of the repair time and has a higher repairing efficiency.

THERMAL RESIDUAL STRESS ANALYSIS OF POLYMER MATRIX CARBONFIBER REINFORCED COMPOSITE WINDING TUBES

LIU Jia-shun, LI Feng, ZHANG Heng-ming

2016, 0(2): 18-23.

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Thermal strain test of polymer matrix carbon fiber-reinforced composite winding tube curing on high temperature was carried out during the process of cooling to room temperature. The thermal residual stress numerical model of composite tube with various plies was established based on hierarchical attributes of the entity unit and the numerical results are in good agreement with the test results. On the basis of the numerical model, from the respect of the stress of fiber direction, the influence factor of thermal residual stress, such as the ply angle, contents of hoop fiber, position of hoop lays and the aspect ratio of the winding tube, are analyzed. The results show that the above influence factors have great influence on the residual stress. The residual stress in the fiber direction of the ply angle of 公式 and the 90°/0° plies orthogonal combination 0° fibers are compressive, and the hoop direction are extensive, which could cause the pipe initial defect micro-cracks.

EFFECT OF GFRP END CONSTRAINT ON BONDING REPAIR

YU Zhou-hui, ZHAO Pei-zhong, HU Fang-you

2016, 0(2): 24-28.

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With epoxy resin as matrix and glass fiber as reinforcing material to form composite patch to repair damage to aluminum alloy, the comparisons were taken without end restraint. Through tensile experiment, the effects on repairing effect with the change of length and layers of the patch were studied after adding constraints at the end of the patch. The experimental results show that the repair effect of layering constraint was obviously higher than that without layering constraint under the same length of patch. At the same time, the rules of the change of the patch to repair effect has not changed after the constraint. Tensile strength increases with the increase of the patch length. When the patch length reaches a certain value, the tensile strength no longer increased, but the initial value has increased significantly. After adopting layering and winding constraint, compressive stress was taken in the interface of FRP-aluminum alloy, the performance of the interface between FRP and aluminum alloy was improved, and the stress concentration of the patch ends was alleviated. Especially, when the patch layer is large, end constraint can effectively improve the difficulty of coordination caused by the increase of layer patch, and winding constraint repair effect is superior to layer constraint.

SIMULATING THE RESPONSE Of THE PVC FOAM SANDWICH PANELSSUBJECTED TO LOW-VELOCITY IMPACT

CHEN Bo, ZHANG Yan-fei, WANG Zhi, ZHAO Gui-zhe

2016, 0(2): 29-34.

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Composite sandwich structure is relactively high susceptibility to damage caused by foreign object impact. This paper established the finite element model of closed PVC foam-based sandwich panels in Abaqus/Explicit based on hashin criterion and crushable foam plasticity model. The precision of the model results was compared with the literature experimental results and its correction was proved. Then, the influence of general contact and surface to surface contact on the contact force history and delamination area, the meshes sizes located on the fined area on the low velocity impact response was simulated by this model. The results show that surface to surface contact is more suitable to simulate the impact response of sandwich panels. Good agreement is achieved between simulation and experiments for force-time curve for impact energy of 4 J. The threshold load can’t be observed, but it can be observed near 0.0005 seconds when the mesh sizes are 1.0 and 1.5 mm.

A STUDY OF ANTI-NOISE PROPERTIES OF MODAL STRAIN ENERGY CHANGE RATIO METHODFOR THE DAMAGE IDENTIFICATION OF FUNCTIONALLY GRADED CLASSICAL BEAM

HUANG Li-xin, YUE Shi-yan, HU Zhong-ming, YANG Zhen-zhen

2016, 0(2): 35-39.

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The anti-noise property of modal strain energy change ratio method is studied for the functionally graded classical beam. Based on the computing platform of the finite element method, commercial software ABAQUS, modal parameters are computed for the free vibration of functionally graded classical beam. Those modal parameters are directly added by Gauss noises with a certain level in order to simulate the measured modal parameters. Three methods are compared for the computation of noise levels. Numerical examples are given to analyze the noise effect on the damage identification results. Numerical results reveal that the damaged element can be successfully identified with 1%, 2% or 5% measurement noise. It means that the modal strain energy change ratio method has very good anti-noise property for identifying damage in the functionally graded classical beam.

STUDY ON MECHANICAL PROPERTIES AND PROCESS PERFORMANCE OF DOMESTIC CARBONFIBER PREPREGS FOR WIND TURBINE BLADE

SONG Qiu-xiang, JIA Zhi-yuan, GAO Ke-qiang

2016, 0(2): 40-46.

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Application of carbon fiber for large structure of wind turbine blades is a developing direction of large-scale wind turbine blade manufacturing technology. To promote the development and application of domestic carbon fiber, this paper presents technical requirements of carbon fiber prepreg in wind turbine blade. Studies on mechanical properties and process performance of the domestic carbon fiber prepreg and imported carbon fiber prepreg were performed. The analysis results show that, mechanical properties of the domestic carbon fiber with lower surface density is higher than imported carbon fiber prepreg, but process performance of the surface density of 600 g/m² for the domestic carbon fiber prepregs is poor, and need to be further improvement.

3D MODELING AND SIMULATION OF MULTI-LAYER WOVENFABRIC WITH COMPLEX FABRIC WEAVE

ZHU Jian-hua, ZHANG Rui-yun, WANG Wei, YU Jian-yong

2016, 0(2): 47-52.

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The four textile structures, three-dimensional angle interlock structure, three-dimensional orthogonal structure, three-dimensional variable thickness structure and three-dimensional tubular structure were simulated, according to the parameters of weaving process and concrete structural data. The cross sections of yarns were supposed as ellipse or round with constant sizes in some structure modeling, and the yarn trajectories were supposed as the cubic B-spline curves. The control points to reconstruct cubic B-spline curves were reversed by selecting data points after determination of location of yarn. Finally, three-dimensional woven fabric is simulated by calling the OpenGL image functions in VC++ programming platform.

PLY OPTIMIZATION OF COMPOSITE LAMINATE BASED ONIMPROVED ADAPTIVE GENETIC ALGORITHM

LU Zhen-yu, ZHANG En-yang,LIU Bo

2016, 0(2): 53-56.

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An improved adaptive genetic algorithm was proposed to improve the efficiency of the composite laminate design based on the genetic algorithm, and its crossover operator and mutation operator can be adjusted automatically in the convergence process. The results of the experiment of the two-dimensional Rasrtigrin trial function show that the proposed algorithm has a better capability in global optimal and convergence speed. Based on the above, the proposed genetic algorithm with integer coding strategy was applied to stacking sequence optimization of composite laminates. The iterative process of an example indicated that 27 iterations was needed for adaptive genetic algorithm and 19 iterations was needed for improving the adaptive genetic algorithm to the global optimal solution. It can be concluded that the improved adaptive genetic algorithm can significantly improve the efficiency of the composite laminate design.

THE DESIGN AND OPTIMIZATION OF CARBON FIBER LAMINATES BASEDON THERMAL STABILITY AND BENDING RIGIDITY

XU Liang, XIE Yong-jie, DING Jiao-teng, WANG Yong-jie

2016, 0(2): 57-61.

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In view of the special application of the carbon fiber composite mirror, the design and optimization of laminated plates are carried out from two aspects: the thermal stability and the uniformity of bending rigidity. The final optimization of the 16 layer [22.5 90 -45 -22.5 67.5 -67.5 0 45]s is the one with the best bending stiffness, but also excellent thermal stability. The design provides a reference for the development of high precision and high thermal stability carbon fiber laminate, and is especially suitable for the application of the design of the deformable mirror.

STUDY ON DISTRIBUTION AND MORPHOLOGY CHARACTERISTICOF VOIDS IN CFRP COMPOSITES

XIAO Peng, LIU Wei-ping, LIU Kui, HUANG Zi-yu

2016, 0(2): 62-66.

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Composite specimen was prepared by changing forming parameters. Ultrasonic testing was used for preliminary detection and screening. Porosity of specimen, voids distribution and morphology characteristic of typical area were counted and analyzed by metallography microscope. Experimental results show that the composite internal voids are caused by insufficient pressure and inappropriate bag vacuum. Pore distribution is inevitable and random, and pore morphology is related to porosity.

STUDY ON A MODIFIED BENZOXAZINE RESIN WITH GOOD FLAMERETARDANCY FOR HOT-MELT IMPREGNATION

ZHANG Qi, JING Mao, RAN Qi-chao, GU Yi

2016, 0(2): 67-70.

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The flame retardant matrixes used for hot melt impregnation were prepared by the blends of benzoxazine and trifunctional epoxy resin. Softening point and adhesion at room temperature of these resin systems were tested. Flame retardancy, Tg and flexural property of cured resins were studied. Results suggest that by adjusting the ratio, the adhesion of the system met the requirement of hot melt technique, and flame retardancy of the cured resins reached UL-94 V-1 grade. Furthermore, limited oxygen index value reached 33, and a glass transition temperature of 212℃ was shown. The flexural strength was as high as 131 MPa. Additionally, the change of the viscosity during curing was adjusted by adding resorcinol as a catalyst. When the addition amount of resorcinol was 2 wt%, the viscosity can meet the requirement during preparation of the composite material. So, a flame retardant benzoxazine resin used for hot melt impregnation was successfully prepared, and it can be used in the aerospace field.

COMPARISION FOR THE APPLICATION OF HIGH MODULUS UD GLASS FABRIC IN WIND BLADE

GUAN Xiao-fang, JIA Zhi-yuan

2016, 0(2): 71-74.

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Tensile properties of glass fiber yarns, ply thickness and 0° tensile properties of the laminated plates for the four kinds of high modulus UD glass fabric are studied. They have close tensile modulus for the glass fiber yarns, and close tensile modulus for the UD composites, when the fiber volume contents are controlled to be similar. However, by vacuum assisted infuse process, the UD composites have different ply thickness, and therefore different fiber volume contents, finally different tensile modulus. When applied in the I-beam with same layer, the stiffness for ply thickness of 0.78 mm increases by about 6% compared with the stiffness for ply thickness of 0.83 mm.

INTERNAL THERMAL STRAIN MEASUREMENT OF COMPOSITES WITHEMBEDDED FIBER BRAGG GRATING SENSORS

JIA Wei-fang, SUN Bao-zhong

2016, 0(2): 75-78.

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This paper studies the internal thermal strain measurement under the temperature range of 20~100℃ by FBG sensors embedded in the center of unidirectional (UD) laminates, and carbon fiber/epoxy plain woven laminates with the Sm125 sensor interrogator. The internal thermal strain properties of both composites under a thermal load were analyzed. The results showed that the internal thermal strains of both composites could be accurately measured using a referenced FBG sensor and the FBG sensors embedded in the center of materials under a thermal load. In addition, the thermal expansion coefficients of both composites were discussed to determine the variation behavior with the increase of temperature. Also, the internal thermal strains of both composites increase with the increasing temperature. It was also found that fabric structure affect the internal thermal strain, and at the same temperature point, the internal thermal strain of plain woven laminates is larger than that of UD laminates.

STUDY ON CYANATE ESTER RESIN MODIFIED EPOXY RESIN COMPOSITE

YANG Zhong, WU Xiao-qing, YANG Hong-na

2016, 0(2): 79-82.

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The epoxy resin was modified by bisphenl-A dicyanate, and the glass fiber reinforced composites were prepared. The effect of the different mass ratio epoxy resin/cyanate ester resin on the co-cured product structure and glass transition temperature were investigated by fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical analysis (DMA), tensile property, flexural property and moisture absorption property of the composites were discussed. The results show that, with the increasing of the content of triazine ring, the content of oxazolidinone decreases as cyanate ester resin increases. When the mass ratio epoxy resin/cyanate ester resin is 50/50, the glass transition temperature of the composite is 215.6℃ and increases by 49.7℃compared to unmodified epoxy resin. After 650 h, water absorption is only 0.69%, but the tensile strength and flexural strength decrease slightly. Scanning electron microscopy (SEM) shows that the residual stress of composites increase with the incorporation of cyanate ester resin, and composites exhibit brittle fracture.

HOT-PROCESSING ASSISTED PREFORM TECHNOLOGY FOR SUPER-THICKCOMPOSITE LAMINATE BY VARI PROCESS

LI Pei-xu, CHEN Ping, HAN Xiao-yong, SU Jia-zhi

2016, 0(2): 83-86.

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Represented by VARI process, the liquid composite molding technology has caused more and more research attention. This article focused on the VARI technology for super-thick composite part and creatively put forward the hot-pressing assisted preform technology. We took 100-layer super-thick laminate by VARI process for example, introduced hot-pressing in the preform manufacture process, and investigated its influence on the thickness of the preform, the resin injection and outlet placement and the quality of the cured composite part. Our work has positive significance for improving the fiber volume content, the performance of the VARI composite parts and the development of the application of VARI technology in aircraft structure. The results will provide reference for the design and application of thick composite parts by VARI manufacture process in aircraft structure.

STUDY ON ELECTRIC STRENGTH OF GF/VE COMPOSITES AT POWER FREQUENCY

TANG Ze-hui, HE Peng, DONG Qing-hai, CHEN Yu-lin

2016, 0(2): 87-90.

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To explore the effect of composite′s parameters on electric strength at power frequency, vinyl ester resin castings and composite plates based on resin transfer molding technology were studied. Tests for electric strength of castings and composites plates parts with different thickness and various cloth orientation were carried out, and the breakdown parts were also fully investigated. It shows that the thickness and fiber cloth orientation of tested parts have some influences on electric strength of composites at power frequency.

DEVELOPMENT OF INVESTIGATION ON THE MECHANICAL PROPERTIES ANALYSIS OF2D BRAIDED COMPOSITES

XIA Yan-mao, QIN Zhi-gang

2016, 0(2): 91-94.

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The development of mechanical properties of 2D braided composites is discussed. Researches on structural geometry model, experimental and theoretical studies for mechanical properties were included. In research of mesoscopic structure, the choice of representative volume unit to establish a reasonable simplified geometric model is most widely used. In the study of mechanical properties, we mainly analyze the elastic performance, and the finite element analysis is the primary analysis method. Finally, some problems of the present study are put forward,and an outlook for investigation trends in future is presented.

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