COMPOSITES SCIENCE AND ENGINEERING

A STUDY OF THE STEADY THICKNESS BY THE VACUUM ASSISTED RESIN INFUSION PROCESS AND THE VACUUM KEEPING TIME

ZHUANG Heng-fei, PAN Li-jian, LIU Wei-ping, TENG Cui-qing

2015, 0(2): 5-10.

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The non-contact electric eddy current displacement sensor system was applied to real-time monitoring of the preform thickness change throughout the vacuum assisted resin infusion (VARI) infusion process. In the other same condition, the influence of the viscosity of resin, filling distance, layer numbers and the permeability on minimum vacuum time to get the steady preform thickness was investigated. The results show that, as the resin overflowed the mould and the resin inlet was closed, continued vacuumed time has an important influence on the thickness/fiber volume fraction, and is beneficial to the decrease of the thickness gradient along the direction of the resin flowing. The effect of the viscosity of resin has the primary influence on the minimum vacuum time for the steady thickness. The higher the viscosity, the longer vacuum time. The filling distance, layer numbers and the permeability has little influence.

STUDY OF THE DAMAGE IDENTIFICATION OF COMPOSITE MODAL FLEXIBILITY CURVATURE BEAM STRUCTURE BASED ON THE RATE OF CHANGE OF MODAL FLEXIBILITY CURVATURE

YU Zhan-hui, YANG Tao, NIU Xue-juan , DU Yu

2015, 0(2): 11-15.

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In this paper, the change ratio of modal flexibility curvature MFCI of composite beam modal was used to discuss the NDT method of composite materials. The natural frequency of the lossy, lossless composite beam and modal displacement amplitude of each node are simulated by the finite element software of ABAQUS. And, the interlaminar damage of composite beam were detected by calculating the MFCI. Then, an example of detecting delamination damage of composite materials with different beams is illustrated, and the results indicate that this method of detecting the composite beam can accurately detect the location delamination damage region whether single-point or multi-point delamination damage and the degree of delamination damage. The simulation results prove that the method of the change ratio of modal flexibility curvature has the significant effect on the judgment of composite beam interlaminar damage.

CHARACTERISTIC TEMPERATURE AND CURING DEGREE OF EPOXY RESIN MATRIX PREPREG DURING THERMAL CURING PROCESS

CHEN Shu-xian, TIAN He, LI Meng, YANG Wen-feng

2015, 0(2): 16-20.

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In order to optimize the curing parameter, the mathematical model for the simulation of the temperature field of resin matrix prepreg during thermal curing process was developed based on the curing kinetics theory and finite element analysis method. The change characteristics of the temperature and curing degree of orthotropic composite during the curing process were numerically studied, and the correctness of the numerical model and methodology was verified by comparing the numerical results with the available experimental results. The effects of heating rate and glass fiber content on the curing characteristic temperatures and curing time of E208 epoxy resin matrix prepreg were studied. The results show that the exothermic peak of curing reaction move to high temperature, and the onset temperature and the final temperature of curing process also increase with increasing heating rate. Thus, it is concluded that the faster the heating rate, the higher temperature gradient and thermal stress occur in the prepreg, while the shorter time is need for completing curing. The results also indicate that the glass fiber leads to lower curing characteristic temperatures and later curing onset time, compared to the epoxy resin. However, the effect of the glass fiber on the curing final time can be ignored for the resin matrix prepreg.

EXPERIMENTAL STUDY OF LONG REINFORCED CONCRETE-FILLED GFRP TUBES COLUMNS SUBJECTED TO ECCENTRIC LOAD

WANG Bao-li, XIN Geng-hua, WANG Qing-xiang

2015, 0(2): 21-27.

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Fifteen long reinforced concrete-filled GFRP tubes columns and one RC column were tested under eccentric load to investigate the mechanical properties of reinforced concrete-filled GFRP tubes column. The failure shape and mechanical properties are studied, and factors such as concrete strength, ratio of length to diameter and eccentricity that affected mechanical properties of the columns are analyzed. Test results indicate that bearing capacity and ductility of the columns are enhanced effectively as a results of the confinement of GFRP tube. Bearing capacity and stiffness of the columns increase with elevation of concrete strength. The confinement of GFRP tube and the bearing capacity of the columns drop with the increasing of ratio of length to diameter and eccentricity. Plane-section assumption is applicable to calculation of long reinforced concrete-filled GFRP tubes columns subjected to eccentric load.

STUDY ON COMPRESSION STRENGTH AND MORPHOLOGY OF CHOPPED CARBON FIBER REINFORCED POLYURETHANE FOAM

YU Xun-zhang

2015, 0(2): 28-31.

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The compression strength and morphology of chopped carbon fiber reinforced polyurethane foam was studied in this paper. The effects of chopped carbon fiber content on the mechanical properties of polyurethane foam were discussed, and the formation conditions of polyurethane foam holes and the destruction of microstructure were investigated by optical microscope and SEM. Results showed that when the chopped carbon fiber content is 30%, the compression strength of polyurethane foam was optimum and the holes were uniform. When the chopped carbon fiber content exceeded 30%, obturators and bubble collapse began to appear, and carbon fiber separated from polyurethane foam and the mechanical strength decreased.

IMPACT OF ACCELERATOR CONTENT ON EPOXY RESIN FOR CARBON FIBER COMPOSITES BY VACUUM INFUSION MOULDING PROCESS

GUAN Xiao-fang, SONG Qiu-xiang, JIA Zhi-yuan

2015, 0(2): 32-37.

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Impacts of accelerator content on epoxy resin were studied systematically by rheometer and DSC analysis for carbon fiber composites in large structural applications by vacuum infusion moulding process. The viscosity behavior, process window, curing characteristics and elemental mechanical properties were analyzed for this epoxy resin with different accelerator content of 0.5%, 1.0%, 1.5%. The optimal infusion temperature didn't change any as the accelerator content increases, but the pot life was obviously shortened. The temperature and time required for complete curing decreased with the increasing of accelerator content. The mechanical properties are almost not affected. Thus, this epoxy resin can be used in ordinary mould.

THE HEAT TRANSFER SIMULATION OF STEEL-COMPOSITE MATERIAL ROCKETS LAUNCHING TUBE

LIAO Gui-chao, LUO Han, ZHU Tong-sheng

2015, 0(2): 38-42.

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The launching tube for rockets which constitute by steel inner lining and composite outer lining has high strength and repeatability but with lower weight. But the coupling structure takes on complex characteristic of thermal under the high temperature rocket jet flow. The simulation of thermal has been done with the ABAQUS software for a steel-composite launch tube, the distribution of temperature for the launch tube has been obtained. The simulation indicates the highest temperature at joint face is 268℃,and the temperature along the tube during 4min refrigeration is basically less than 150℃ except the both sides. The analysis results indicate that the thermal action of jet flow to the launch tube is very strong. The study provides theory warranty for the structure and thermal design of the tube, and has important references to the choice of composite material and bond.

RESEARCH ON THE SHAPE FOR WEB ROOT OF LARGE WIND TURBINE ROTOR BLADE

ZHAO Na, ZHU Xiao-qin, LI Cheng-liang

2015, 0(2): 43-46.

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Different root shape of shear web, result different stress distribution of web, especially for the weak parts may be caused blade damage due to the stress superposition. This article discusses the influence of different web root shape on the stress distribution of dangerous area. By calling the proportion coefficient of web root excision shape to C-type form factor F, the paper uses three ways to discuss the C-type form factor. By combine the result of finite element analysis and practice, the best shape of web root was finally determined.

STUDY ON SURFACE MODIFICATION OF PBO FIBER AND ITS INTERFACIAL PROPERTIES WITH RESIN MATRIX

LI Zhong-yi, JU Su, SHI Gang, LUO Ying-she

2015, 0(2): 47-50.

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Two different surface treatment methods, single treatment process (such as “chemical treatment”, “plasma treatment”, “coupling treatment” and “radiation treatment”) and combined treatment processes (such as “radiation & plasma treatment” and “radiation & plasma & coupling treatment”) were used for the surface modification of PBO fiber, respectively. Then, the tensile strength, contact angles and interface bonding strength of the treated fibers were tested. The results show that, PBO fibers treated by the combined ways have better integrated properties: the residual tensile strength is about 85.1% of the untreated fiber; the contact angel between the treated fiber and water is 74.15°; the bonding strength between combined treated fiber with epoxy resin is 48.6% higher compared to the untreated fiber.

PROPERTIES OF SW280 FABRIC/BENZOXAZINE PREPREGS PREPARED BY HOT MELT IMPREGNATION

SHI Han-qiao, DING Chang-fang, SUN Bao-gang, CHENG Lei

2015, 0(2): 51-55.

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Glass fabric-reinforced benzoxazine prepregs were prepared by hot melt impregnation. The process and thermogravimetry of the benzoxazine resin were studied. And the dynamic thermomechanic analysis, mechanical retaining at high temperature and flame retardant properties of the prepregs were also investigated. The softening point of the benzoxazine resin was 41~42℃ and the lowest viscosity was 1835 mPa·s, which were suitable for the preparation of prepregs. In nitrogen atmosphere, the initial degradation temperature of benzoxazine resin was about 280℃, and the char yield was about 61.3% at 800℃. The mechanical and interface properties of the SW280 fabric/benzoxazine prepregs were excellent. The Tg of the composite was about 200℃. The retention ratios of the compression strength,flexural strength, flexural modulus, and interlaminar shear strength at 200℃ were 90.6%, 59.4%, 83.2%, and 62.7%, respectively. The flame retardancy of the composites was excellent. The maximal smoke density was 0. The oxygen index was ＞58%. The vertical burning level was V-1.

THE CORROSION RESISTANCE STUDY OF ISO-PHTHALIC & TERE-PHTHALIC POLYESTER RESINS IN ALCOHOL CONTAINING GASOLINE ENVIRONMENT

JIN Li-xin, PENG Ji-mei, YU Hao, LV Jin-yan

2015, 0(2): 56-59.

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The primary duty of a corrosion resin is to provide the required performance characteristics for its intended environment but often another critical requirement is to provide aesthetic characteristics, which are sometimes a problem to achieve with high molecular weight resin of a crystalline nature. Reduced molecular weight resins will provide improved glass wetting and aesthetics, but these reduced molecular weight polymers may not have the same corrosion performance as their higher weight counterparts. In this study, A 2∶1 (2 moles of maleic∶1 mole of terephthalic∶3 moles of propylene glycol) terephthalic based polymer and a 2∶1 (2 moles of maleic∶1 mole of isophthalic∶3 moles of propylene glycol) isophthalic based polymer with Mw values incrementally increasing from 6000 to 20,000 to determine what is the minimum Mw value required to provide satisfactory corrosion performance in gasohol blends will be compared. Physical property performance retention data will be presented for the various Mw values of the two polymer types. The conclusion analyzed by the physical property retention performance is terephthalic based polymers has a better anticorrosion property than isophthalic based polymers in gasoline alcohol blend.

INFLUENCE OF HEATING ON THE PHYSICAL PROPERTIES OF FIBER REINFORCED PLASTICS

LUO Li-ping, ZHANG Li-song

2015, 0(2): 60-63.

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Fiber reinforced plastics (FRP) consist of two major components: glass fiber and organic resin. Significant changes in FRP′s physical properties can be found as it goes through a series of physical and chemical evolution under heating conditions, which would further influence the internal temperature distribution of the material. Models regarding the changes in FRP′s physical properties can be set up by studying this process under heating. Using FRP samples, the cool-side temperature was recorded during arc-jet tests, which can be further compared with the results of the simulated calculations from the model. Since the calculated and the arc-jet results match each other very well, this model is suggested to be reliable for the engineering reality.

PREPARATION AND PROPERTY RESEARCH OF NOMEX HONEYCOMB REINFORCED PHENOLIC FOAM

LI Ju-ying, LI Ying, WEI Hua-zhen, SUN Xiao-dong

2015, 0(2): 64-67.

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Nomex honeycomb reinforced phenolic foam was produced through special foaming craft,from the matrix phenolic foam and the reinforcement Nomex honeycomb. The effect of matrix and that of the interface on mechanic and thermal conductivity were analyzed through the performance characterization of micro-structure, machanics and thermal conductivity. It was obviously found that the mechanics was enhanced and thermal conductivity was reduced after phenolic foam was filled in Nomex honeycomb. It was concluded that the form of the hard interface made the phenolic foam benefited to the increase of machanics and the decrease of thermal conductivity and it was still a good fire retarding and heat insulating material.

APPLICATIONS OF EPOXY FAST CURING TECHNOLOGY IN THE UAV STRUCTURE REPAIR

LIU Chang-liang, BAO Chuan-mei, LIU Lin, CHENG Jian

2015, 0(2): 68-71.

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Three different mechanisms of epoxy resin fast curing were analyzed. Curing experiments were carried out to comparat curing time, tensile strength, hardness and toughness. Based on the measured data and focusing on field environment UAV the body repairs, and by using AHP preferred embodiment, the UV curing is ultimately to achieve even repair requirements.

ANALYSIS ON RING STIFFNESS OF REINFORCED FRP PIPELINE

CHENG Ai-lin, ZHANG Guo-jun, YANG Da-wei

2015, 0(2): 72-74.

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The ring stiffness is an important performance parameter of buried FRP pipes, and also the resistance to radial deformation, affecting bearing capacity under external pressure. In this paper, ring stiffness is analyzed theoretically, and the formula are basically the same with that of experimental analysis, which verified the rationality of experimental analysis and calculate methods of reinforced FRP pipeline. And, the research methods and results will serve as a reference to the design, manufacture and application of FRP pipeline.

EXPLORATION OF INTERFACE COMPATIBILITY OF ARAMID FIBER/EPOXY PREPREG

SUN Wen-dan, LI Bo, LI Gang, YANG Xiao-ping

2015, 0(2): 75-80.

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A good match of resin matrix and reinforced fibers was necessary for prepreg. Therefore, the surface modification of aramid fiber and the toughening of epoxy resin were summarized to improve the interface compatibility of aramid fiber/epoxy prepreg. The merits and demerits of the physical and chemical modification of surface of aramid fiber were discussed. Various toughening methods of interphase and epoxy resin were analyzed and PU(polyurethane)/EP(epoxy) IPN(interpenetrating polymer network) was highlighted. The combination of surface modification of aramid fiber with coupling agents and PU toughening epoxy resin was suggested to be a practicable approach to improve the interlaminar shear strength (ILSS) of aramid fiber/epoxy prepreg.

PROGRESS IN THE STUDY ON MECHANICAL PROPERTIES OF ANCHORAGE SYSTEM FOR CFRP CABLES

LIU Li-hua, ZHU Yuan-lin, ZHANG Ji-wen, ZHOU Zhu-bing

2015, 0(2): 81-86.

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A review of studies on the mechanical properties of anchorage system for CFRP cables is given in this paper. The emphasis is placed on the recent achievements in this field, in which the experimental and numerical simulation investigations into anchorage system are included. Important developments in this field are discussed. The strength of CFRP tendon can′t be into full play in wedge-type anchorage, and a progressive damage method of predicting the strength of wedge-type anchorage system should be established by using the finite element method. In order to accelerate the engineering application of CFRP tendon, the fatigue characteristics and stress relaxation of anchorage system for CFRP tendons must be further studied. A new structure of CFRP stay cable was proposed, which was advantageous to anchorage and application. In the end, the prospects of some essential areas to be researched on CFRP cables are previewed.

APPLICATION TENDENCY OF COMPOSITE MATERIALS FOR SLIDE-WAY LAUNCHER

SHAN Qi-yi, ZHANG Kun, LIU Le-qing

2015, 0(2): 87-90.

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Application and development of composite materials for slide-way launcher were introduced in this paper. The foreign technological situation of the composite reinforced missile launcher was reviewed. In addition, some key problems, including the structure/damping integration technology, moulding technology of structural composite and nondestructive inspection technology, were comprehensively analyzed. Finally, the view that the composite material was important to the progress of the slide-way launcher in future was presented.

Industry information contents

2015, 0(2): 91-128.

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