COMPOSITES SCIENCE AND ENGINEERING

EDGEWISE COMPRESSION PROPERTIES FOR HONEYCOMB SANDWICH STRUCTURE WITH PLAIN WOVEN FACEPLATE

WANG Xuan, CAO Yang-li, DENG Yun-fei, YU Ji-yuan

2018, 0(8): 5-11.

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In order to study the edgewise compression properties for honeycomb sandwich structure with plain woven faceplate, failure modes of honeycomb sandwich structure were divided into three types: faceplate failure, honeycomb failure. And, adhesive failure, and edgewise compression damage analysis models of honeycomb sandwich structure with plain woven faceplate were established. The honeycomb sandwich structure were predicted by the model based on progressive damage analysis. The test on edgewise compression properties of honeycomb sandwich structure were conducted. By the comparative study of the prediction and experiment results, their failure strength fitted well. The results show that the damage initiation, damage progression, and final damage during the edgewise compression of honeycomb sandwich structure can be simulated accurately by the damage analysismodel established in this paper, and finally the edgewise compression failure strength can be predicted.

BOLTED JOINTS CONNECTION STRENGTH & DAMAGE EVOLUTION ANALYSIS BASED ON FIBER MAPPING

NIE Xin, MO Cheng-jie, YAO Wei, XIONG Dong-jian

2018, 0(8): 12-18.

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The main types of the bolt connection strength and the damage failure of the injection molding glass fiber reinforced composites (GFRP) in the body structure have been studied. Mechanical properties tests of the PA6 GF30 materials have been carried out, based on Multicontinuum materials decomposition theory, fiber mapping and fitting materials curve to obtain their simulation parameters. Compared with the results of simulation and experiment, it showed that based on material decomposition, fiber mapping, curve fitting of the simulation analysis method, we can effectively solve the problems between moldflow analysis and structure analysis continuously and accurately. Based on the accurate mapping information of GFRP, the bolt connection strength and damage failure modes between GFRP were studied, and comprehensive studies of E/D, W/D and T/D on the strength of bolt connection were performed. The results show that the main forms of connection failure are tensile failure and extrusion failure, and the factors that affect the connection performance are W/D, T/D and E/D. With the increase of the E/D and the W/D, the bolt connection strength increases, but the ratio no longer increases after a certain number, which is mainly manifested as the extrusion failure. Increasing the T/D can significantly increase the bolt connection strength.

EFFECT OF DAMPING LAYER THICKNESS ON DAMPING STRUCTURE LOSS FACTOR OF EMBEDDED CO-CURED COMPOSITES

WANG Shao-qing, LIANG Sen, Qiao Yan-mei, LIU Bing-guo

2018, 0(8): 19-24.

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The strain energy of individual stress components is studied using Ritz method, and the loss factor of the embedded co-cured composite damping structure is calculated. The law of loss factor variation with the change of the damping layer thickness is obtained. The results show that when the total thickness of the thin plate is constant and the thickness of the damping layer increases from 2 mm to 5.5 mm, the loss factor increases with the increase of the damping layer thickness. When the damping layer is thick, the loss factor is no longer sensitive to the change of the thickness of the damping layer. When the thickness of the composite layer is constant, the loss factor increases with the increase of the thickness of the damping layer. When the thickness of the damping layer is thick, the thickness of the damping layer has little effect on the modal loss factor. Compared with the constant thickness of the composite layer, when the total thickness of the thin plate is constant, the thicker damping layer has a smaller influence on the loss factor.

EXPERIMENT STUDY ON BEARING CAPACITY OF GLUED-IN REBAR T-JOINT BETWEEN WOOD SANWICH-FRP COLUMN AND BEAM

YONG Wei-yi, QI Yu-jun, FANG Hai, LIU Wei-qing

2018, 0(8): 25-31.

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A connector of FRP column to beam was designed. FRP column was fastened to beam by one of two methods: adhesive bond and glue-in rebar. According to shear-rotation test, mechanical properties and failure mode were investigated. Moreover, shear-rotation response, joint rotational stiffness and bearing capacity were also studied. The results show that specimen TJ3 has a better elastic property and bearing capacity. Compared with TJ2 and TJ1, the bearing capacity is increased by 2 and 4 times. Moreover, TJ3 presented the shear failure and the other three specimens presented the flexural failure under nearly joint loading. The distribution of rebar stress of TJ2, TJ3 and TJ4 is consistent, and the maximum tensile stress all occurs at connected interface between conector and column.

TRANSIENT EFFECT OF UNIDIRECTIONAL CONTINUOUS CFRP IN ELECTRIFYING

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

2018, 0(8): 32-35.

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The voltage response of unidirectional continuous carbon fiber reinforced plastics (CFRP) in electrifying to stable stage was studied with different flowing currents. In the case of current greater than or equal to 300 mA, the resistance of the CFRP specimen was found to decrease dramatically initially and become stable gradually after 100 s. The greater the current is, the more quickly the resistance varies in the initial stage and the greater the resistance change is in the stable stage. The temperature of CFRP increases gradually and the temperature curve is similar to transient response curve. In addition, the temperature change in the stable stage also increases with the increase of the current. The results reveal that transient effect of unidirectional continuous CFRP is mainly caused by the temperature sensitive response due to the ohmic heating. Based on the experimental results, for the purpose of accurately measuring the resistance change, a few suggestions were made on the applications of CFRP as piezoresistive sensors.

TOOL PATH POSTURE OPTIMIZATION FOR COMPOSITE AUTOMATED FIBER PLACEMENT

WANG Xian-feng, YE Zi-heng, WANG Ruo-zhou, ZHAO Cong

2018, 0(8): 36-41.

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In order to improve the manufacturing efficiency of Automated Fiber Placement (AFP), a posture optimization algorithm, which based on High Speed Manufacturing research, is proposed. During AFP manufacturing, due to the unfairness of orientation change, servo motors are required to accelerate and decelerate frequently to meet the manufacturing orientation requirements, which limits the process rate. In order to increase the efficiency, according to the flexibility of the rubber roller, the admissible orientation domain based on the roller coordinate system is established. Under the constraint zone, the rotation curve is optimized by Butterworth digital filter and objective optimization function, which contributes to the increasement of manufacturing efficiency. According to data analysis and practical placement experiment, the optimized tool path has a better fairness property in rotation axis motion and acceleration curve. Besides, the manufacturing efficiency has been improved compared with the original two paths.

RAPID STACKING SEQUENCE OPTIMIZATION OF COMPOSITE STIFFENED PANELS CONSIDERING STABILITY

ZHANG Chang-xing, DUAN Shi-hui

2018, 0(8): 42-47.

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Stacking parameters and the engineering common layer library were used in the stacking sequence optimization of composite stiffened panels, the initial buckling load of the structure was improved without changing the weight of the structure. Due to the large number of FEA calculations and the long calculation time during the optimization process, a fast analysis method for stability of composite stiffened panels which is based on energy method was chosen, whose calculated values are similar to the experimental values and the FEA results. In the optimization process, the stacking parameters were taken as the design variables, and were optimized by MATLAB optimization toolbox. Then, the optimized results are compared with the stacking parameters of the layer library, and the most closed stacking sequence is selected using least square method. Finally, the energy method and finite element method were used to verify whether the buckling load of the optimized structure is improved. The example shows that the optimization method has short operation time and high optimization efficiency, and the buckling load of the optimized stiffened plate is increased by more than 17%.

EXPERIMENT STUDY ON THE FLEXURAL BEHAVIOUR OF HYBRID BFRP/STEEL REINFORCED CONCRETE BEAMS

KONG Xiang-qing, YU Yang, XING Li-li, HAN fei

2018, 0(8): 48-54.

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A total of ten concrete beams, including one reinforced with BFRP, one reinforced with steel, and eight reinforced with hybrid BFRP and steel, were designed and prepared. Experiment tests were carried out to investigate the effect of reinforcement area ratio on the flexural behaviour of hybrid BFRP/steel reinforced concrete beams with a low and high reinforcement ratio. The flexural capacity, failure mode, flexibility deformation, crack distribution and ductility performance of the hybrid BFRP/steel reinforced concrete beams were analyzed and compared with the BFRP reinforced beam as well as the steel reinforced beam. The results indicated that there are two main failure modes: the hybrid BFRP/steel reinforced concrete beams with high reinforcement ratio fails by crushing of concrete in compression and either yielding of steel and the test beams with low reinforcement ratio fails by crushing of concrete in compression and either rupture of FRP in tension. The load-deflection curves of the hybrid reinforced concrete beams show three linear characteristics including the turning points corresponding to the cracking load and the yield of the steel bars. The ultimate bearing capacity of the hybrid reinforced concrete beams, which is found to be increased with the increase of area ratio, is slightly lower than that of BFRP reinforced concrete beams, but it is higher than that of reinforced concrete beams. The ductility of hybrid reinforced concrete beams are all larger than that of steel reinforced concrete beams. The lower the reinforcement ratio, the greater the reinforcement area ratio and the higher the ductility coefficient. To meet the requirements of structural seismic design specifications, it is recommended that the reinforcement area ratio is controlled to be not less than 0.6.

EFFECT OF MCNTS ON THE CURE OF VINYL ESTER RESIN AND INTERLAMINER ADHESION OF SUCH PULTRUDED GLASS FIBER COMPOSITES

CHEN Shang-neng, SHEN Ming-xia, LU Feng-ling, ZENG Shao-hua

2018, 0(8): 55-60.

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Benefiting from good mechanical properties, superior corrosion resistance and low cost, vinyl ester resin (VE) is widely used to yield corrosion resistant products. However, the disadvantage of low interlaminar shear strength (ILSS) still exists in the pultruded glass fiber-reinforced VE composites. To resolve the above problem, industrial multi-wall carbon nanotubes (MCNTs) were firstly dispersed in VE with the help of mechanical stirring at alternating speeds, and then glass fiber-reinforced VE composites containing MCNTs (MCNTs/GF/VE) were fabricated by pultrusion at low cost. The effect of free radical trapping effect of MCNTs on the ILSS and the thermal property of pultruded composites were evaluated. The results showed that proper supplementary of initiators can compensate for the loss of free radicals due to the free radical trapping effect of MCNTs, and ultimately increased the ILSS and glass-transition temperature (T_g) of MCNTs/GF/VE composites. With the incorporation of 0.1wt% MCNTs into VE, the ILSS and T_g of composites were increased by nearly 20% and 8.1 ℃, respectively, as compared with those of the composites without MCNTs. Moreover, the interlayer adhesion and heat resistance of the composites could be further improved with the decrease of pull-speed due to the improved curing degree of VE. The interfacial adhesion of the composites was enhanced by chemical or physical crosslinking interactions among MCNTs, VE and glassfibers.

STUDY ON ALKALI RESISTANCE OF VINYL ESTER RESIN WITH LOW ESTER DENSITY

LIU Shi-qiang, MAO Ling-feng

2018, 0(8): 61-65.

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Corrosion resistance of five different types of vinyl ester resin and unsaturated polyester resin was tested under the same experimental conditions in order to compare the corrosion resistance of low ester density in alkali with other different type resin. The alkali was sodium hydroxide (NaOH) solution, for which the mass fraction was 25% and temperature is 80 ℃. The test proved that low ester density had excellent alkali resistance at high temperature. The flexural strength retention rate is 75%, the flexural modulus retention rate is 105%, the mass retention rate is 98.6%, effective thickness change rate is less than 0.5%, and barcol hardness retention rate was 108% after soaking 600 days in 25% NaOH solution.

SIMULATION AND OPTIMIZATION STRUCTURE AND THERMAL DEFORMATION OF HIGH PRECISION COMPOSITE ANTENNA REFLECTOR

XING Si-yuan, LIU Hong-xin, PENG Zhi-gang, ZHANG Yu-sheng

2018, 0(8): 66-73.

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Two kinds of finite element analysis (FEA) software, Hyperworks and MSC.Patran/Nastran, were employed to analyze the structure and thermal deformation in the different working conditions of high precision composite antenna reflector. And, Hyperworks was used to optimize the studied antenna reflector structure. The numerical solutions derived from these two types of software are similar in the calculations of composite antenna reflector strength, mode and thermal deformation. The results show that Hyperworks and MSC.Patran/Nastran are universal in the composite structure and thermal deformation simulation. The modal frequency results derived from simulation software are close to that of sinusoidal vibration experiment, which indicates that the veracity of simulation software is high. Furthermore, the optimization results from Hyperworks show that the structure mass reduces by 8.5% and the modal frequency increases by 19.7% in the studied antenna reflector.

RESEARCH ON BENDING PERFORMANCE OF CUTTAGE GRAFTING COMPOSITE MATERIALS TRANSMISSION TOWER

WANG Hong-yun, SUN Hai-yang, WEI Xi-long, CAI Jin-gang

2018, 0(8): 74-79.

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This paper presents a kind of transmission tower that is composed of hollow tapered cuttage grafting poles applied in 66 kV voltage grade. Transmission tower′s main bearing beam is connected together through the way of cuttage grafting according to electric design specifications. Meanwhile, transmission tower′s structure is designed, and deflection formula of variable section of point load is proposed. The influence of fiber winding angle and thickness on poles stiffness is analyzed by the classical laminated theory. The finite software ANSYS is applied to analyze the whole pole′s bending performance about different transition lengths. Each cuttage grafting pole is manufactured by a small angle winding technique. The real model test of the tower installation wire, broken line, wind load and other working conditions is carried out. Finally, the results show that the form of the cuttage grafting composite tower has a good bending and a fatigue resistance, which meet the requirements of transmission tower.

EFFECT OF ZB FLAME RETARDANT ON PROPERTIES OF EPOXY RESIN COMPOSITES

ZHAO Zhi-ying, LIANG Hong-tao, PENG-Fei, WANG Shao-min

2018, 0(8): 80-82.

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Epoxy resin-based reinforced composites have many important applications in the aerospace and other fields. With the continuous upgrading of material properties and requirements, it is a new issue to improve the flame retardancy of composite materials. In this paper, ZB flame retardants were added to epoxy resin. The results of the extreme oxygen index (GB/T 8924) and the TG test indicated that the initial decomposition temperature of the epoxy resin was increased. In addition, the thermal decomposition temperature of the epoxy resin increases with the addition amount of the flame retardant. Then, the epoxy resin composite panel were prepared by adding different amounts of ZB flame retardant. Mechanical properties and tilt ablation tests were carried out, which showed that the flame retardant properties of epoxy composites was increased with the addition of ZB flame retardant. However, the tensile strength and compressive strength were decreased with the addition of ZB flame retardant.

STUDIES ON SEMI-CIRCLE DEPTH INFLUENCE ON COMPRESSIVE PROPERTIES OF COMPOSITE STRINGER OF AIRCRAFT

ZHANG Ming-xing

2018, 0(8): 83-88.

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Semi-circle depth stringer end samples of center wing are made, and compression test is carried out. Load-strain curves under axial compression load were obtained. The results show that non-linear deformation appeared, and the failure load is greatly influenced by the semi-circle depth. Failure load increases with the semi-circle depth. The largest strain appears on the first row fasteners on the rib flange and skin.

STRUCTURAL ANALYSIS AND DESIGN OF HOISTING INDUCED SELF-FORMING GFRP ELASTIC GRIDSHELL

XIANG Sheng, ZOU Le, CHENG Bin

2018, 0(8): 89-95.

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The hoisting induced self-forming GFRP elastic gridshells, which consist of long-continuous GFRP circular tubes, are such structures whose shapes are formed as a result of elastic deformations due to gravity during the hoisting process. By referring to existing design codes and literatures, analysis and design of such gridshell are conducted. Finite element model is established, in which multi load cases are considered. The structural responses regarding construction stage, serviceability limit state, ultimate limit state as well as stability are checked according to code provisions. The results show that the displacements, stresses, bearing capacities, and stability coefficients of the structure satisfy the design requirements.

STUDY ON THE PRINCIPLE OF AERODYNAMIC REHABILITATION

YUAN Jian-chao, WANG Guo-dong, HUANG Ping-chao, FANG Hong-wei

2018, 0(8): 96-101.

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The development status of the composite blade general strip theory and airfoil numerical simulation method is briefly described. A method of two-dimensional flow field analysis is used to deal with the different states of a typical airfoil section, so the stress nephogram and velocity nephogram in different states are obtained. According to the stress condition and gas velocity distribution in various states, the applicable area and basic requirements of the principle of aerodynamic rehabilitation are discussed and derived. The repair principle and prospect of composite blade are prospected.

ULTRASONIC TESTING METHOD FOR EDGE BONDING OF COMPOSITE BLADE

GAO Xiao-jin, ZHOU Jin-shuai

2018, 0(8): 102-105.

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The new type aero engine fan blade adopts the structure of the composite edge bonding with thin metal skin. According to the material and structure characteristic of blade edge, we analyzed the applicability of the ultrasonic penetration method and the ultrasonic reflection method to test blade edge bonding quality, and proposed the method of combining ultrasonic C-scan penetration and high resolution ultrasonic A-scan reflection. The results show that the proposed method can test all the Ⅰ and Ⅱ interface artificial debonding defects of 5 mm×5 mm, and can effectively test the debonding defects in the actual products.

PROGRESS IN RESOURCE RECLAMATION OF THERMOSET POLYMER COMPOSITES

ZHANG Li, ZHANG Yi-he, WANG Lei, TIAN Mou-feng

2018, 0(8): 106-113.

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Extensive application of thermoset polymer composites (TSPC) has led to excessive waste. Recycling and utilization of TSPC waste is becoming a new problem which the industry community and society are facing with. In this review, we summarized the progress of recycling and reuse of TSPC. First of all, the physical and energy recycling methods are briefly outlined. Particular emphasis is placed on chemical recycling method. Then, the current status of reclamation of TSPC waste in aviation, automobile, recreation and entertainment, construction and other fields are listed and summarized. Finally, the existing problems in reclamation of TSPC waste and the counter measures that should be taken are discussed.

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