COMPOSITES SCIENCE AND ENGINEERING

THE STATIC TEST OF THE COMPOSITE ANCHOR FOR CFRP TENDONS AND THE ANALYSIS OF THE BOND STRESS DISTRIBUTION

CHEN Bei, LI Shi-quan, LIU Rong-gui, XIE Gui-hua

2015, 0(11): 5-8.

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The tests of parallel composite anchors for CFRP tendons are carried out. The wedge-bond anchorage with reasonable parameters can anchor 8mm-diameter CFRP tendons effectively. By strain test of steel pipes, the distribution of the bond stress of reinforcement is obtained. This method is simple and reliable, especially for the type of anchor. In the ultimate state, the stress distribution of M-7 is consistent with BBA model. While the stress distribution of M-1, M-2, M-3 is not consistent with BBA model, and is mainly reflected in the loading end. The bond stress is significantly higher than the residual bond stress of BBA model. The results showed that the anchoring performance and bond stress are influenced by gripping position, bonding materials, the length of steel pipe and clip. The results provide a basis for the design of large-tonnage anchor structures of the same type.

THREE-DIMENSIONAL NUMERICAL SIMULATION RESEARCH OF THERMAL CONDUCTIVITY OF Cu/EP COMPOSITE

LU Man, BAO Rui, YAN Shi-lin, SHAO Shi-dong

2015, 0(11): 9-14.

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Thermal conductivity of Cu/EP composite was studied by numerical simulation method. A 3D model of particles random distribution was established by ANSYS/APDL parametric finite element analysis technology. The effect of model size, volume fraction, single particle size or normal distribution particle sizes, particle shape, particle size and particles distribution on thermal conductivity of Cu/EP composites were investigated. The simulation results show that when the length of thermal conductivity model is greater than 100μm, the thermal conductivity is close to stabilization. Thermal conductivity of Cu/EP composite increases with volume fraction, and the magnitude of increase becomes bigger and bigger. Filling same particle size particles and normal distribution particle sizes particles, thermal conductivities of them keep pace with each other. Particle size has effect on thermal conductivity, and the change law is not monotonous increasing or decreasing. Cube fillers enhance the performance of thermal conductivity better than sphere fillers. The thermal conductivity will be different for different particles distribution in the matrix. When the particles are arranged along the direction of heat flow, the enhancement is significant.

SIMULATION FOR STRUCTURE DAMAGE INDENTIFICATION OF WIND TURBINE BLADE BASED ON MODE STRAIN ENERGY THEORY

ZHANG Xin, GU Gui-mei

2015, 0(11): 15-19.

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To solve damage identification problem of wind turbine blade structure in different cases, a stepwise method based on unit mode strain energy change rate and BP neural network is used. Change of mode strain energy per unit is compared to judge damage preliminarily. A mapping model is built for reflecting the relationship between the characteristic parameter and damage state to indentify the location and degree of damage, and the mode strain energy change rate is treated as characteristic parameter characterized structure damage. The results show that unit mode strain energy can judge possible damage unit effectively, and BP neural network can indentify structural damage location and degree more accurately. The method has good recognition effect for many damage cases.

DEFORMATION MONITORING FOR GFRP STRUCTURES BY CFRP SMART LAYER

ZHENG Hua-sheng, LI Jing, ZHU Si-rong, LI Zhuo-qiu

2015, 0(11): 20-24.

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For the purpose of long-term real-time health monitoring for GFRP structures, composite made of short-cut carbon fiber mat and epoxy resin was applied as a smart layer for deformation measuring. The piezoresistivity of the smart layer was studied by cyclical tension test, and it was applied on a three point bending beam. The stable VA characteristic and piezoresistivity were confirmed in CFRP smart layer. Under cyclical tension, the resistance of CFRP smart layer was observed to increase linearly and reversibly with stability. Based on its piezoresisitivity, the resistance of the CFRP smart layer is able to reflect the bending deformation of the GFRP beam whether it is on the tension side or compression side. Furthermore, the results reveal that such a method can be affected by electrode configuration: the resistance responses of four-probe method are more stable, but the gauge factors are comparatively low, which is 5.9 for four-end probe method and 7.3 for four-surface probe method; two-probe method can improve the gauge factor to 13.1, but is inferior to four-probe method in stability.

EFFECTS ON BUCKLING BEHAVIORS OF COMPOSITE LAMINATES WITH HOLES

DU Yu, YANG Tao, NIU Xue-juan

2015, 0(11): 25-29.

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In this paper, the finite element model of the composite laminates with holes is built by ABAQUS. Laminated plates with simply supported edges under axial pressure loads, the effects of d/w, ply proportion, lay-up angle, material properties on buckling load were analyzed. The results show that the bigger the d/w, the smaller the buckling load. When d/w is less than or equal to 0.1, it is considered to be a small hole. When the proportion of the 90° is larger, the ratio of the 0 degree is smaller, the buckling load is larger, and the ratio of the 45° is increased, and the anisotropy degree of laminated plate is decreased. The lay-up angle has a great influence on buckling load, the difference between the maximum and the minimum value is 13.05N. The main directional parameters of the material are different, the buckling load also has a big difference, and the performance parameters of the material have obvious influence on the buckling load.

PLASTICS RIBBED PIPE BASED ON FINITE ELEMENT METHOD

CHENG Xiong-fei, CHEN Jian-zhong, CUI You-guo, SONG Yin

2015, 0(11): 30-33.

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Glass fiber reinforced plastics ribbed pipe is a kind of excellent performance pipeline structure. Because its structure is more complex than smooth surface pipe, there is no good way to design it. The finite element calculation method for ring stiffness of glass fiber reinforced plastics ribbed pipe was determined by analyzing the concept of ring stiffness. Then, on the basis of optimization design theory and method, the optimization design for glass fiber reinforced plastics ribbed pipe structure is studied based on finite element method by software ANSYS. First, the thickness of pipe is determined according to the internal pressure. Then, under the condition of meeting the ring stiffness design value, the design of the distance between two ribs and the height of rib cross section are optimized in order to obtain the lightest weight. It has an important significance for the design and application of glass fiber reinforced plastics ribbed pipe.

STUDY ON FLEXURAL AND COMPRESSIVE PROPERTIES OF PBO FIBER AND T700 CARBON FIBER HYBRID COMPOSITES

ZHANG Cheng-shuang, CUI Xia, LI Cui-yun, WANG Bai-ya

2015, 0(11): 34-37.

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The flexural and compressive properties of PBO fiber and T700 carbon fiber hybrid composites were studied in this paper. The effects of hybrid ratio on flexural strength and modulus, compressive strength and modulus of hybrid composites were examined by a universal testing machine. Flexural and compressive failure mode of PBO/T700 hybrid composites was also discussed. The results indicate that the flexural strength and compressive strength of PBO fiber reinforced composite increased from 542MPa and 233.2MPa to 1120MPa and 702MPa after hybridization with T700 carbon fiber. The flexural and compressive failure mode of PBO fiber reinforced composite and T700 carbon fiber reinforced composite were typically ductile failure and brittle failure, respectively. The flexural and compressive failure mode PBO/T700 hybrid composites shift from ductile failure to brittle failure with increasing of the hybrid ratio.

FINITE ELEMENT ANALYSIS ABOUT THE TENSILE DEFORMATION OF COMPOSITE CELL UNDER INTERNAL PRESSURE

TANG Ze-hui, WANG Peng-fei, DONG Qing-hai, CHEN YU-lin

2015, 0(11): 38-41.

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To estimate the influence of tensile modulus and thickness of composite cell on the tensile deformation, the commercial finite element ANSYS software was applied to this study. The results show that it will help to decrease the tensile deformation by increasing the tensile modulus and thickness of cell. However, the deformation is nonlinear with the tensile modulus and the thickness. The most appropriate value of the tensile modulus and thickness were determined based on the calculations of ANSYS, and it will not only effectively control the tensile deformation of the cell, but also can low cost and simplify the process engineering.

THE TEST AND FULL-RANGE NUMERICAL ANALYSIS OF COMPOSITE STIFFENED LAMINATES UNDER STATIC INDENTATION FORCE

HUANG Fei-sheng, ZHOU Shi-gang, GONG Zhan-feng, LUO Teng-teng

2015, 0(11): 42-46.

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Based on the user subroutine USDFLD and Hashin's criteria, this paper presented a finite element composite stiffened laminates damage model by using ABAQUS software. Six basic damage models such as delamination, matrix crack and matrix compression, fiber fracture and fiber crush may happen when composite stiffened laminates are under static indentation force, the damage evolution of composite stiffened laminates can be simulated by this finite element damage model. Load-displacement curve and dent depth-load curve of composite laminates were predicted by the finite element composite stiffened laminates model. The computed results are in agreement with the corresponding experiment result, which proves the validity of the presented damage model. The pit depth of the composite stiffened laminates at the knee of curve increased obviously. Compared with unstiffened plate, the dent depth of the composite stiffened laminates came to 0.84mm,which was considered as a visible impact damage. The method and results concluded in the paper can be useful for the performance analysis of grid-stiffened composite structure such as the rear pressure bulkhead used in aircraft.

MECHANICAL PROPERTIES OF RAMIE FIBER AND GLASS FIBER REINFORCED UNSATURATED POLYESTER COMPOSITES

CHEN Xu,ZHANG Hu,LIU Yan-feng,YI Xiao-su

2015, 0(11): 47-52.

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Unsaturated polyester-based composites reinforced with ramie fiber and glass fiber was prepared by Vacuum Assisted Resin Infusion (VARI) process. Different kinds of hybrid composites were studied. It was found that the sandwich structure which glass fiber as shell and ramie fiber as core (GRUP) has better mechanical properties than the sandwich structure which ramie fiber as shell and glass fiber as core (RGUP) in the same hybrid ratio. And, the mechanical properties of the interplay hybrid composite (IPUP) are between the two kinds of composites. Different hybrid ratios under the same sandwich structure were studied. It was found that the content of ramie fiber and the mechanical properties are negatively related. The relationship between the content of ramie fiber and the tensile strength as well as the tensile modulus follows a linear function, while the flexural strength and modulus are complied a cubic curve with the content of ramie fiber.

DURABILITY OF UNSATURATED POLYESTER RESIN BASED AND EPOXY VINYL ESTER RESIN BASED GLASS FIBER-REINFORCED PLASTICS COMPOSITES

NIE Ya-nan, MA Dong-yang, WANG Cheng-qi

2015, 0(11): 53-58.

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In recent years, GFRP composites are gradually used to wrap ocean engineering structures, which act as substitutes of anti-corrosion paints or coatings, working as protective layers to prolong the service life of these ocean engineering structures. In order to research the durability of GFRP composites in ocean environment, hydrothermal aging, freeze-thaw aging and ultraviolet aging were adopted to study the corrosion behavior of glass fiber-reinforced plastics composites in ocean environment. The mass variation rate, retention rate of bending strength and SEM were used to analyze the corrosion mechanism and durability of 189 unsaturated polyester resin based and MFE-2 epoxy vinyl ester resin based glass fiber-reinforced plastics (GFRP) composites. The results show that the number of ester group on the resin molecular chain is the main factor that affects the durability of GFRP composites in ocean environment. The number of ester group on the MFE-2 epoxy vinyl ester resin molecular chain is about 1/3 of the 189 unsaturated polyester resin. To be concludes, the MFE-2 GFRP possesses better durability in ocean environment.

THE RESEARCH ON THE SELECTION OF CARBON FIBER CORE CONDUCTORS WITHIN THE WHOLE LIFE CYCLE ANNUAL COST

YANG Chang-long, TIAN Chao-kai, WANG Zhi-wei, SHAO Xiao

2015, 0(11): 59-63.

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The carbon fiber composite core conductor (CFCC conductor) feature has series of advantages, such as light weight, large ampacity, cost-saving of the poles, reduction of the occupied area and etc. However, the cost calculation model based on the CFCC conductors' whole life cycle has not yet been formed. In this paper, taking the practical engineering as example, we calculate the annual cost within the whole life cycles by different selections, analyze and compare the results with corresponding ASCR conductors to obtain the selection method which can take full advantage of the CFCC conductors, provide practical and reliable method and basis for engineering design and decision making.

EXPERIMENT RESEARCH ON TEMPERATURE-RISING LAW OF SELF-HEATING AIRFIELD PAVEMENT WITH CONTINUOUS CARBON FIBER HEATING WIRE

LI Chun-ming, XU Wei, LI Qiang, LIU Xiao-guo

2015, 0(11): 64-70.

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Aiming at self-heating airfield concrete pavement with continuous carbon fiber heating wire, three cement concrete pavement slabs were made, which respectively inbuilt 6K,12K and 24K carbon fiber heating wire, and the temperature-rising law of plates were studied through field experiments in different natural environment and input power. The results indicate that the more closer the heating wire, the faster the temperature could rise and the higher temperature could reach. Temperature of different points on the same plane of each concrete slab surface was less than 3℃ when spacing was 10cm, and the temperature uniformity was good. The results of temperatre-rising were mainly determined by the input power.The temperature of slab surface could rise to 0℃ after 3.5 hours with the -10℃ natural temperature and 382W/m² input power. The natural environment has significant effects on the temperature-rising of slab surface. The variation tendency of temperature on slab surface was always in correspondence with the environmental temperature. The temperature on the slab surface would reduce by more than 20% when the environment temperature reduced 3℃. The thermal dissipation of concrete slab changed slowly, and the surplus thermal energy could be used for melting snow and ice.

STUDY ON THE EFFECTS OF TOUGHNESS MODIFICATION ON THE PROPERTIES OF GLASS FABRIC REINFORCED PHENOLIC COMPOSITES

LI Ya-feng, HONG Xu-hui

2015, 0(11): 71-74.

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Three kinds of PVB (polyvinyl butyral) with different molecular weight were selected to improve the toughness of glass fabric reinforced phenolic resin composites. The climbing drum peel strength, 60 second vertical burning test, smoke density and the heat release rate of toughened composites were measured. By this way, the effect of molecular weight and additive content of the toughener on the toughness and fireproof properties of composites was estimated. It was found that higher molecular weight resulted in higher peel strength flowing with the degression of fireproof properties. The interlaminated strength of composites was obviously enhanced by three kinds of PVB. The increase of 29%, 81% and 71% was obtained by additive of lower, moderate and higher molecular weight PVB, respectively.

EFFECT OF RESIN TYPE, FABRIC TYPE, THICKNESS ON RESIN CONTENT OF FRP BY VARI

WANG Gang, MA Yan-mei, DONG Yuan-yuan, XU Jun

2015, 0(11): 75-77.

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Effects of various resins, fabrics and thickness on resin content of glass-fiber reinforced plastic (GFRP) molded by vacuum assistant resin infusion process (VARI) were studied in this paper. Experimental results indicate that resin content of GFRP prepared with triaxial-fabrics is higher, while resin content of GFRP prepared with biaxial-fabrics and unidirectional-fabrics is lower. The resin content of GFRP prepared with high viscosity resin (LR135/LH135) is lower, while resin content of GFRP prepared with low viscosity resin system (035C/037) is higher. When the thickness of fabric increases, resin content of the GFRP decreases.

STUDY ON ANTIBACTERIAL MILDEWPROOF PROPERITIES OF NOMEX HONEYCOMB SANDWICH

ZHAO Zhi-ying,ZHU Xiu-di,YANG Kai,SUN Yi

2015, 0(11): 78-80.

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In this study,we prepared by adding antibacterial fungicide and without adding antibacterial fungicide honeycomb sandwich composite materials. Based on NH-1-2.75-32 Nomex honeycomb core material land mixing resin impregnated glass cloth presoak material for composite panels, the two kinds of Nomex honeycomb sandwich composite materials mechanical properties and antibacterial mouldproof performance were tested. We found that, by adding antimicrobial agent,the horizontal and longitudinal shear strength and the shear modulus were improved. Meanwhile, the aramid honeycomb composite exhibited excellent mildew antibacterial proof property, such as Escherichia coli, Staphylococcus aureus, Candida albicans,Staphylococcus epidermidis.

THE RESEARCH STATUS OF INSULATED CONNECTOR IN PRECAST INSULATION WALL PANELS

WAN Chao-yang ,CHEN Guo-xin

2015, 0(11): 81-84.

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This paper introduced that the insulated connector related features of precast sandwich insulation wall panel, summarized the research status on mechanical properties and the anchorage performance of insulated connector with concrete which was affected by many factors both at home and abroad, referenced the relevant specification and insulated connector used technical requirements, prospected the research on insulated connector.

RESEARCH DEVELOPMENT OF GLASS FIBRE REINFORCED NYLON 6 COMPOSITES

LI Yue-wen

2015, 0(11): 85-89.

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Research development about factors influencing property of nylon 6(PA6)/ glass fibre (GF) composites, compounding process of the composites, interphase treatment, and synergism modification of GF and third component on PA6 were reviewed in this study. The increase of GF content is propitious to improve mechanics and tribology property of PA6/GF composites. The improvement effect of long GF on the composites is better than that of short GF. Surface treatment of silane coupling agent, rare earths and compatibilizer on GF is conducive to improve interface combine strength, and increase integration property of the composites. Addition of nanometer SiO₂ and Si₃N₄ into PA6/GF composites is propitious to improve mechanics and tribology property of the composites, and addition of nanometer clay is able to improve its mechanics and flame retardant property. Addition of carbon nanotubes into the composites is not only able to improve its mechanics property, but also able to improve its antistatic and flame retardant property. Addition of styrene/acrylonitrile/maleic anhydride copolymer and polythene into the composites is conducive to depress its hygroscopicity, and addition of UHMWPE is able to improve its tribology property. Flame retardant containing phosphorus and GF have synergism effect on improvement of flame retardant property of the composites.

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