COMPOSITES SCIENCE AND ENGINEERING

STUDY OF ENDS ANCHOR METHOD OF STRESS RELAXATION SPECIMENS OF FRP TENDONS

YUAN Guoqing，DONG Guohua，MA Jian

2009, 209(5): 3-6.

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As prestressing tendons, the stress relaxation property of FRP tendons must be studied. To survey it, the key is to find an effective method anchoring the specimen’s ends. The usual FRP tendon anchor systems are not fit to measure the stress relaxation property. Therefore，an innovation anchor method has been put forward in this paper. Applied the anchor system，the slip of the specimen’s ends is nearly zero so that the strain of the test section can be maintained constant during the test and the measure results should be accurate.

MECHANICAL CALCULATION AND COEFFICIENT ANALYSIS OF CFRP IN BONDED BEAM

ZHANG Peng, HAO Xian-Wu

2009, 209(5): 7-9.

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Based on the elastic theory and some assumptions of composite section, the concrete beam strengthened with carbon fiber reinforced polymer (CFRP) is analyzed, the expression of micro element interfacial shears and the differential calculus of axial force in the CFRP are established. Then the analytical solutions of the axial force in the CFRP, the interfacial shear stress and the bonding moment on the section of beam are presented as general forms. CFRP strengthening function coefficient Kf and endregion stress concentration factor k are put forward to explain the strengthening mechanism, stress concentration phenomenon and the influencing factors. Combined with an example, the suggestion for the stress concentration is proposed.

STUDY ON NATURAL FREQUENCY OF LAMINATES WITH CUTOUT

LU Xiang, LI Ding-He, Feng-Zhen-Yu, XU Jian-Xin

2009, 209(5): 10-13.

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The existence of the cutout has a great effect on the structural mechanical performance. Based on MSC.Patran, a finite element model was developed to study the free vibration response of square composite laminates with oneedge simply supported and having an eccentrically circular or rectangular cutout. Along the size of cutouts were increasing, natural frequencies of composite laminates with circular or rectangular cutout were obtained by this finite element model. The variety laws of natural frequency along with shape and size was fitted. The results show that the natural frequencies of composite laminates with circular or rectangular cutout are reduced compared with the natural frequencies of composite laminates with no damage. The influence of rectangular cutout on frequency is more severe than circular cutout. The influence of litter cutout damage on natural frequency is not evidence.

STUDY ON FIBER CONTENT IN COMPOSITES PRODUCED WITH FINE POWDER
DIPPING TECHNOLOGY BY FLUIDIZED BED

JI Tao, HUANG Xiao-Mei, YU Jin, LI Xua-Jia

2009, 209(5): 14-17.

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With the fluidized bed technology, the continuous fiber reinforced thermoplastic plastics composites were prepared from glass fiber, carbon fiber, PP and PA6. The effects of electrostatic voltage, air pressure and dipping time of dipping technology on the fiber content were studied. The results show that the higher resin content can be gained by higher air pressure, electrostatic voltage and longer dipping time. The kind of reinforced fiber and the kind and size of resin affects the fiber content as well.

ELASTICITY SOLUTION OF SIMPLESUPPORTED COMPOSITE
BEAMS WITH DELAMINATIONS

YAO Xiu-Dong, Zhou-Ding, LIU Wei-Qiang

2009, 209(5): 18-22.

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Taking the twolayer simplesupported composite beam with one delamination as example, this paper studies the effect of delamination on the stress and displacement distributions of the beam under static loads. Separating the beam into two parts along the delamination, the elasticity solution of each layer has been given respectively. The vertical point forces are used to replace the distributive contact stresses between the upper and lower surfaces of the delamination. The interface equations are regrouped along the beam length. The new interface equations are expanded by using the Fourier transformation. Combining to the condition of zero vertical displacements at contact points and using the sign of the contact forces to distinguish the case of true contacts, the interference of the displacements between the upper and lower surfaces of the delamination has been successfully solved by using the iterative calculations. High accuracy solution has been obtained. Excellent consistency of the present solutions and the finite element solutions from the commercial program ANSYS has been observed.

STUDY ON THICKENING CHARACTERISTICS OF UNSATURATED POLYESTER RESIN

ZHANG Lan-Fen, WU-Dun, Liu-Chun-Lin

2009, 209(5): 23-26.

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In this paper, the effects of the type and content of thickening agents, thickening temperature and the type of filler on the viscosity of unsaturated polyester resin were studied by Physica MCR 301 rheometer. Otherwise, the thickening mechanisms of MgO and MDI were studied by acid value titration and infrared analysis respectively. The research results showed that,four kinds of thickening agents had different thickening rates, in which MgO was the fastest. As the content of thickening agents increased, the thickening rate increased. The thickening rate also increased with the increasing of the thickening temperature. The addition of fillers made viscosity increase, and different fillers had different effects, compared to CaCO3，the effect of ATH was bigger at the same content. Therefore, many factors should be considered to acquire appropriate thickening process in industrial production.

EXPERIMENTAL RESEARCH ON FLEXURAL BEHAVIORS OF PARTIALLYPRESTRESSED
AND PARTIALLYBONDED CONCRETE BEAM REINFORCED WITH CFRP BARS

ZHANG Feng, DENG Lang-Ni, DENG Yu

2009, 209(5): 27-30.

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The new concept of “partiallybonded” was proposed for the first time in China. The loading process, failure mode,loadingdeflection property, ductility performance and effect of prestress degree were analyzed， by the static loading experiment of nine partiallybonded mixed reinforcement concrete beams reinforced with CFRP bars and epoxy resin coated steel bars. Test results show that the mechanical behavior of prestressed concrete beam reinforced with CFRP bars can be improved by using the partiallybonded and mixed reinforcement mode, provide the design calculation method of concrete beam reinforced with CFRP bars with important reference value.

THE BUCKLING OF VARIABLESTIFFNESS COMPOSITE PANELS WITH
CURVILINEAR FIBER FORMAT

MA Yong-Jian, ZHANG Chu-Jie, XU Zhen-Yu

2009, 209(5): 31-35.

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This paper presents a study on the concept of variablestiffness with curvilinear fiber format. Based on that concept, the redistribution of stress field occurs, which improves the buckling load of the laminated composite panels. By using ABAQUSTM, it proves the model of the concept and shows that the increment of the buckling load is significant, which is 14%.

EFFECT OF THERMOOXIDATIVE AGEING ON PROPERTIES OF HEMP FIBER/UNSATURATED
POLYESTER RESIN COMPOSITES

LEI Wen, YANG Tao

2009, 209(5): 36-41.

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The unsaturated polyester resin reinforced ①hemp fiber composites were formed by compression molding process, the thermooxidative aging test was carried out for 600h at 105℃. The mechanical properties of different composites before and after aging were studied, and the changes of the structures of different materials through the aging test were investigated by FTIR technology, the morphologies of the fractured surfaces of some composites were observed by SEM.The resultshows, treating the hemp fiber with silane coupling agent KH570 has the best comprehensive positive effect.The tensile strength, tensile modulus, flexural strength, flexural modulus and impact strength of the KH570 treated composite are correspondingly 19.06MPa, 5.78GPa, 52.988MPa, 1.01GPa and 3.881kJ/m2 after aging for 600 hours，which indicate that the composite still has the best mechanical properties.The FTIR spectra of the KH570 treated composite are almost the same before and after the test, and some absorbances are even strengthened. SEM pictures show that the fibers still dissipate in the matrix of the KH570 treated composite homogeneously after aging for 600 hours.

RESEARCH ON MECHANICAL PROPERTIES OF CONTINUOUS GLASS FIBER REINFORCED
THERMOPLASTIC/THERMOSETTING COMPOSITE

GUO Shu-Liang, DUAN Ti-Xin, ZHAO Xing, LUO Yun-Feng

2009, 209(5): 42-45.

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Continuous glass fiber reinforced thermoplastic/thermosetting composites(GF/EP/PC) and glass fiber reinforced thermoplastic composites(GF/PC)were prepared by thermomolding process，and comparative analysis of influencing factors of mechanical properties was made. The results showed that tensile elasticity modules and flexure modules of GF/EP/PC composites were respectively 16.4 times and 8.8 times of GF/PC composites, and tensile strength and flexure strength respectively increased 17 times and 37 times. Considering the mechanically damaged appearance photos and the fracture appearance (SEM)，the failure mode and the interface between fiber and resin were analyzed.

TEST METHOD AND IMPROVEMENT ON FATIGUE OF GLASS FIBER REINFORCED PLASTICS

PAN Li-Jian, JIN Jiao-Tong, PENG Chao-Xi, ZENG Jing-Cheng

2009, 209(5): 46-48.

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The improvement on the testing clamp and the size of the specimen was conducted for fatigue of glass fiber reinforced plastic．A new fatigue testing and appraising method on glass fiber reinforced plastics was introduced by using the dumbbellshaped specimens with tensile testing holes．The distribution of stress in specimen was analyzed by FEA,proper specimen structures were obtained. The fatigue tests were carried out for GFRP under two different stress levels. The results show that all the specimens are failure in the test area, the method put forward is verified.

LOWVELOCITY IMPACT RESPONSE OF HOLLOW INTEGRATED
SANDWICH COMPOSITES WITH ALUMINUM SKIN

ZHOU Hong-Chao, QIAN Kun, CAO Hai-Jian, LI Hong-Shun

2009, 209(5): 49-52.

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This paper presents experimental investigations on lowvelocity impact response of hollow integrated sandwich composites with aluminum skin by using dropweight method. The drop weight during impacting is obtained and recorded by acceleration transducer and the corresponding signal processing system. Based on the acceleration record, the impact force and impact displacement, energy absorption versus time can be calculated. The effects of aluminum skin on the impact characteristics such as peak force, contact duration, maximum deflection and absorbed energy are also examined. Results of the study indicate that the provision of additional aluminum skin enhances the damage resistance, such as contact stiffness, the peak load and initial damage of energy.

191# UNSATURATED POLYESTER/GFRP ARTIFICIAL ACCELERATED AGING RESEARCH

WANG Yun-Yang, ZHAO Qing, MENG Jiang-Yan, ZHU Chun-Ya

2009, 209(5): 53-56.

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The aging behavior of 191# unsaturated polyester resin and its GFRP have been studied by artificial thermooxidation aging and artificial xenon arc lamp aging. The morphology and glossiness of specimens were investigated by microscope and glossmeter respectively. The yellowness index (YI) was tested by differential colorimeter. The unsaturated polyester resin was analysed by FTIR and DMA. The tensile strength and bend strength of the specimens were measured. With aging evolving, the appearance of the specimens changed more and more yellow, its glossiness reduced, and appeared some crack on the sample’s surface. These changes were related to the aging mode. The DMA showed that after xenon arc lamp aged 90d, Tg of the resin was from 84℃ to 88℃, and to 83℃after aged 240d, and its storage energy decreased gradually. Mechanical strength of the specimens increased at first then decreased. The aging of the resin and its composites were more susceptible to xenon arc lamp than thermooxidation.

OPTIMAL DESIGN OF COMPOSITE STIFFENED PLATES

MU Peng-Gang, WAN Xiao-Peng, ZHAO Mei-Yang

2009, 209(5): 57-60.

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The optimization techniques of composite blade stiffened plates have been established with the genetic algorithm in this paper. The genetic algorithm using the multiparameter concatenated coding is applied to the layout optimization of the number and height of stiffeners, thickness of stiffeners and panel of composite stiffened plates. The results of the examples indicate that the methods proposed are available, and show us a new way to structural optimization problem.

FAILURE ANALYSIS ON SILICON SANDWICHED OF FIBER REINFORCED PLASTIC PIPE

MA Xiao-Meng, DU Juan, LIAO Shi-Xin

2009, 209(5): 61-64.

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According to a bursting accident of silicon sandwiched FRP pipe in petrochemical process water system, this paper analyzes failure mechanism of FRP pipe based on the mechanical property test, macroscopic and microscopic observation. The countermeasures for selection and operation are put forward.

THE APPLICATION OF FUSIBLE CORE MOLDING IN COMPOSITE PROCESS

SHI Xi-Peng, LIU E-Jing, ZHANG Yan-Fei

2009, 209(5): 65-68.

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In this paper, the shaping processes of moulding, the transfer moulding and injection moulding of meltable alloy core in the fibre reinforced composite are studied. The moulding principles,manufacturing process, actual examples and perspectives of the application are given.

PREPARATION AND ANALYSIS OF NEW BENZOXAZINE RESIN WITH
ETHYNYL AND ALLYL GROUP

ZHANG Ying-Jiang, XU Wei, WU Hai-Xia, MEI Li-Wen

2009, 209(5): 69-71.

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Benzoxazine with allyl group and alkyne group prepared by using 3ethynylaniline, diallylbisphenol A and formaldehyde in 1,4dioxane was synthesized, and characterized by 1H NMR and FTIR in this paper. The benzoxazine compound is liquid in room temperature. Dynamic mechanical analysis (DMA) was used for analyzing the cured product of benzoxazine compound. The results show that the cured product of benzoxazine compound has higher application temperature, its glass transition temperature can reach 367.61℃. Therefore,it could be used as a resin matrix of high performance composite.

VIBRATION CHARACTERISTICS OF NATURAL FIBER REINFORCED COMPOSITE VEHICLES

FANG Meng-Xia, QUAN Wei-Zhuo

2009, 209(5): 72-77.

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High speed, light weight and low energy consumption have become the major goals for the car manufacturers all over the world. Besides the light weight, good tailorable and mechanical performances, natural fiber reinforced composites (NFRCs) have environmentfriendly property. The major objective of this paper is to investigate the dynamic characteristics of the vehicles whose body parts are made from NFRCs. The free interface component mode synthesis method was employed to set up the dynamic system model possessing nonlinear and coupled rigidelastic properties. Then the vibration characteristics of the vehicle under different road and engine excitation conditions were simulated in timehistory. The obtained results were compared with those of vehicles having steel body parts. Based on the above study, the design principle of vehicle bodies made by NFRCs was proposed. This would provide theoretical basis for the large scale applications of NFRCs in automobile industry.

THE INTEGRAL MANUFACTURE TECHNICAL STUDY OF LARGE LENGTHDIAMETER
RATIO COMPOSITES LONGTAIL NOZZLE

LIU Feng, YANG Hua-Jun, FENG Xue-Mei

2009, 209(5): 78-80.

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A integral manufacture technical of large lengthdiameter ratio composites longtail nozzle was presented in this paper. The choice of materials，design of mould and manufacture techniques were investigated in details. The carbon/carbon throat and copper sintered tungsten nozzle were wound in the middle of longtail nozzle insulation ·Compare with the traditional manufacture technipues，the integral manufacture techniques could improve the production efficiency，quality reliability and integrity and reerosion capability.

THE APPLICATION OF VACUUM ABSORPTION TECHNOLOGY ON
FRP WIND POWER PRODUCTS

FU Xiu-Jun, LI Li-Min

2009, 209(5): 81-83.

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As a simple molding method with low cost, absorbingvacuum molding could make wind power products effectively. It is suitable for making complex structures in large size, because the products have low porosity and good performance.

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