COMPOSITES SCIENCE AND ENGINEERING

MULTI-SCALE MODELLING OF UNIDIRECTIONAL COMPOSITE UNDER LONGGITUDINAL TENSILE LOADING BASED ON THREE-DIMENSIONAL LOAD TRANSFER MECHANISMS

PAN Yue-xiu, YU Ya-lin, ZHU Shi-peng, QI Guo-cheng

2015, 0(6): 5-11.

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In this work, a 3D finite element model was established as a representative volume element (RVE) to analyze the load transfer mechanism of the unidirectional composite. The load transfer efficient and ineffective transfer length was defined in the model. The Monte-Carlo simulation was conducted based on the Weibull distribution of the tensile strength in a single fiber, which can simulate the progressive failure process and predict the failure strength of the composites. The data of the tensile strength of the single fiber for Toray T700 and T800 carbon fibers along with the same level of domestic carbon fibers GCT700 and GCT800 were tested. The Weibull distribution function was obtained by fitting the experimental results of single fiber tensile tests. The longitudinal tensile properties of unidirectional composites manufactured via autoclave process were investigated for the validation of the numerical model. Simulation of the progressive failure process was conducted for the composite and the predicted tensile strength of the unidirectional composite was obtained. Furthermore, the experimental and simulated results for different unidirectional composites were compared. The predicted values were in accordance with the experimental results, which proved that the model was valid for the failure process and strength prediction.

RESEARCH ON REACTION CHARACTERISTICS OF CBT RESIN AND MECHANICAL PROPERTIES OF THEIR GLASS FIBER REINFORCED COMPOSITES

MU Shu-xiang, DU Wei

2015, 0(6): 12-17.

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The reaction characteristics of cyclic butylene terephthalate (CBT) resin, CBT100 and CBT160 resin, were analyzed. The influence of three kinds of tin catalysts on CBT100 resin low viscosity pot life and polymerization time at high temperature was studied. Glass fiber reinforced poly(cyclic butylene terephthalate) (PCBT) composite materials were prepared by resin powder melting and impregnation molding process and high temperature vacuum assisted resin transfer molding (VARTM) process respectively and their mechanical properties were compared. The research result showed that CBT160 resin reacted rapidly at high temperature and it was suitable for molding processes similar to resin powder melting and impregnation molding process. CBT100 resin could obtain proper pot life and polymerization time by adding certain amount butyl tin tris-2-ethyl hexanoate or butyltintris(2-ethylhexoate) catalyst, enabling it suitable for high temperature VARTM process. Glass fiber reinforced PCBT composites prepared by high temperature VARTM process using CBT100 resin and butyl tin tris-2-ethyl hexanoate catalyst has excellent mechanical properties, which was slightly better than that made by powder melting and impregnation molding process using CBT160 resin.

STUDY ON MECHANICAL AND WAVE-TRANSPARENT PROPERTIES OF MODIFIED CYANATE ESTER-BASED COMPOSITES

SUN Yu, XU Ren-xin, ZHENG Cong-wei, WANG Jun

2015, 0(6): 18-22.

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The cyanate ester resin was modified with the low dielectric modifier, and the composites were prepared from the quartz fiber and modified cyanate ester resin. The fracture surface of the matrix and composites were characterized by SEM. The heat resistance and mechanical properties of modified cyanate ester resin were studied. The mechanical properties of composites were analyzed as well as the wave-transparent properties of composites. The results show that, the glass transfer temperature of modified cyanate ester resin exceeds 200℃. The fracture of the modified resins belongs to ductile fracture. The tensile strength, flexural strength and compressive strength of the resins exceed 27MPa, 69MPa and 148MPa, respectively. The interfacial compatibilities of the modified cyanate ester resin and quartz fiber were favorable. The tensile strength, flexural strength and compressive strength of composites exceed 447MPa, 461MPa and 259MPa, respectively. As the frequency between 0.5GHz and 18GHz, the dielectric constants of composites are between 3.1 and 3.3, and the S₂₁ of 4mm samples are less than -1.6dB.

RESEARCH ON BEARING CAPACITY AND SHEAR STRESS DISTRIBUTION OF COMPOSITE PRE-TIGHTENED TEETH CONNECTION IN TENSION AND COMPRESSION

XU Long-xing, CHENG Ying, CHEN Li, XU Pan-feng

2015, 0(6): 23-28.

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Pre-tightened tooth connection (PTTC) is a novel connection for composite tubes which has high connection efficiency. The PTTC single tooth plane joint in tension and compression was studied in this paper. The bearing capacity and shear stress distribution of the single tooth joint were compared in tension and compression. The digital speckle correlation method (DSCM) and contact analysis numerical methods are used to analyze the shear strain of specimens. The study shows that the bearing capacities are almost the same with the same factors in tension and compression, but the shear stress distribution of the shear area of the tooth is different. This conclusion can be used in the design and calculation of pre-tightened tooth connection (PTTC).

IMPACT ON THE SURFACE OF BASALT FIBER AND COMPOSITE MATERIAL PROPERTIES OF LOW-TEMPERATURE PLASMA TREATMENT

JIN Ting-ting, SHEN Shi-jie, LI Jing, ZHAO Shu-ping

2015, 0(6): 29-35.

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In this paper, low-temperature plasma was used as a method of the basalt fiber surface treatment.Low temperature plasma treatment on fiber surface properties and adsorption capacity of the coupling agent were studied and the fiber surface treatment on basalt fiber reinforced epoxy (BFRP) gluing and mechanical properties of composites were investigated. The results show that: the contact angle of basalt fiber surface with low-temperature plasma treatment decreases from 132.23° to 75.22°, which greatly improves wettability. The adsorption capacity of coupling agent of the fiber surface achieves the maximum at 10 times with low temperature plasma treatment. With the low temperature plasma treatment and coupling agent treatment, tensile properties and rapidly properties of basalt fiber reinforced epoxy resin (BFRP) composites reach maximum at 10 times, and the shear strength increases rapidly from 2 to 10 times and it becomes stable after 10 times.

RESEARCH ON THE SPREAD WIDTH OF FIBER BUNDLE DURING THE PREPARATION OF PREPREG BY DIRECT IMPREGNATON METHOD

XIE Fei, WEN Li-wei, XIAO Jun, LI Zhi-hui

2015, 0(6): 36-41.

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The spread width of fiber bundle is a key factor which influences the quality of prepreg for AFP (Automated Fiber Placement) during the manufacturing process by direct impregnation method. With the help of high-speed digital image sensor, the spreading process of the fiber bundle by the rods or rollers in zig-zag fashion under different processing parameter was analyzed. The results indicate that the rod has much stronger effect on spreading fiber bundle than the roller. By increasing the fiber tension or wrap angle as well as decreasing the distance between the adjacent rod and roller, the fiber bundle can be spread wider. Furthermore, the spread width of the fiber bundle increases when the fiber operation speed is low. However, the excessive fiber tension will lead to an unstable spreading process, which could cause the fiber bundle separating and fiber breaking. The results provide guidance on the manufacturing process of the prepreg for AFP.

STRUCTION OPTIMIZATION OF COMPOSITE CASE DOME WITH HOLES BASED ON CDOE

YANG Le, FU Ting-ting

2015, 0(6): 42-47.

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Numerical was used to analyze the foe dome with holes of filament winding composite case. Based on the CDOE, 8 cordorinte value of the fore dome were defined as design point by establishing surrogate model and GDO. Meanwhile, target function was introduced which contained weight of the foe dome with holes and Mises-strain along the fiber located in the pitch circle of the hole edge for optimization design.The results reveal that the structure of the foe dome was correspond,and strain distribution located in the pitch circle was reasonable,the weight of structure was decreasd by 1.85%.

THE EFFECTS OF ELECTRIC ON THE IMPACT DAMAGE CHARACTERISTICS AND RESIDUAL COMPRESSIVE STRENGTH OF ELECTRIFIED CFRP COMPOSITES

JI Zhao-hui, LIU Gang, WANG Zhi-ping, LI Na

2015, 0(6): 48-52.

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The electric-thermal damages were studied in the paper and are performed on carbon fiber reinforced polymer (CFRP), the surface temperature field of electrified CFRP specimens was measured by the self-devised damage test device. The resistance variation with current magnitude was measured for the CFRP composites. When comparing the initial resistances at the onset of the electric current applications for the same specimen subjected to the currents of different magnitudes, it was found that resistance decreased with an increase in the current magnitude. We have also investigated experimentally the influence of the current application on the impact response of CFRP. The relationship between damage area, compressive strength after impact (CAI) and current magnitude was discussed. The major damage mechanism of electrified composites under compressive load was also analyzed. It was demonstrated that the current density plays an important role in the impact damage resistance of electrified composites: in contrast to a low current application that has almost no effect on the CAI of the tested composite, a stronger application of an electric current apparently had a detrimental effect on the composites. The dent depth and impact area increases rapidly with the increasing of current after 20A.

THREE-DIMENSIONAL TOPOLOGY OPTIMIZATIONAL DESIGN OF COMPOSITES MICROSTRUCTURE OF LARGE-SCALE WIND TURBINE BLADE

XIE Gui-lan, XIAO Chun-ya, HE Li-cai

2015, 0(6): 53-57.

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Three-dimensional topological design of composites microstructure of large-scale wind turbine blade was conducted to achieve its lightweight properties in this paper. By homogenization theory, the effective elasticity of composite reinforced by carbon fiber was derived from the equivalent homogenized microstructure. Optimization model was established by using solid isotropic material with penalization (SIMP) model to build the relationship between the design variables and the macroscopic elastic modulus. In the model, the relative density of each element was defined as design variables, the volume fraction of overall solid material as optimization constraints,the weighted sum of main diagonal elements of the equivalent elasticity modulus matrix as objectives. Optimality criteria combined with sensitivity filter technique was applied to control the distribution of the material. The problem was solved under MATLAB platform. Numerical results of different objectives show correctness and efficiency of the proposed optimization model and have some influences on the lightweight design of wind turbine blade.

BUCKLING STABILITY RESEARCH ON THE MAXIMUM CHORD REGION OF WIND TURBINE BLADE TRAILING EDGE

SU Cheng-gong, LI Cheng-liang, LU Xiao-feng

2015, 0(6): 58-63.

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The structure of wind turbine blade is usually shell at the maximum chord region of the trailing edge. It have a large deformation under the wind load, and it is the more frequent damage area. The finite element eigenvalue buckling analysis method is adopted in this paper. We analyzed the effect on buckling factor and blade weight (cost) of several different structure forms about skin design, add ribs and install third web. The relationship between blade weight and the buckling factor under the different structure was compared, in order to find the best stability and cost optimal design scheme. The results show that install third web is the best design scheme of optimal cost, light weight, when the buckling factor is the same.

STABILITY ANALYSIS AND NATURAL FREQUENCY CALCULATION OF COMPOSITE CAP-BEAM

JIANG He, ZHENG Bo

2015, 0(6): 64-68.

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According to the Classical Lamination Theory, this paper deduced the effective flexural rigidity of cap-beam with the relationship between the internal force and strain when the beam are under the pure bending state. Then, the effective flexural rigidity was used to deduce the axial critical load and the natural frequency of this beam. Finally, the finite element method was used to verify the formula, providing a reference for the application of the cap-type and other section types of composite beam in engineering.

COMPARATIVE RESEARCH OF DATA ACQUISITION AND ANALYSIS SOFTWARE FOR SMALL AND MEDIUM OPEN COOLING TOWER THERMAL PERFORMANCE TEST

ZHANG Li-xin, XU He-hua, YIN Zheng, GAO Ming

2015, 0(6): 69-72.

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Two sorts of data acquisition and analysis software have been put forward based on C# language and configuration software for small and medium open cooling tower thermal performance testing process. Through comparative analysis of two kinds of software applied in thermal performance testing process, their advantages and disadvantages in terms of data acquisition, processing and calculation are obtained. Based on which we propose more reasonable, facile solutions for the thermal performance test of cooling tower.

DESIGN METHOD AND ENGINEERING EXAMPLE OF CONCRETE PANELS STRENGTHENED BY COMPOSITE GRID WITH SKIN

QIAN Zhen, FANG Hai, LIU Wei-qing, OUYANG Yi-zhen

2015, 0(6): 73-78.

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This paper proposes a new FRP-concrete composite panel form-concrete panels strengthened by composite grid with skin. The effective bending stiffness of this kind of panels was deduced by the transformed section method. And the mid-span displacement was derived from mechanics of materials method. It brings up a whole structured design process of a sandwich structure bridge panel, and gives the design parameter of bridge panel. The checking results show that using concrete panels strengthened by composite grid with skin into girder-composite bridge panel is more feasible.

CONDITIONS ON VOLATILE CONTENT ANALYSIS OF PHENOLIC-BASED PREPREG

ZHENG Zhang-yi, HUANG Zhi-xiong, DING Jie, LUO Hai-tao

2015, 0(6): 79-83.

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In order to get the best conditions on volatile content analysis of phenolic-based prepreg, production technology, composition and curing mechanism have been analyzed and we designed a series of contrast test of phenolic-based prepreg at 80℃, 90℃ and 100℃ at a series of different holding time. The condition on accurate analysis for phenolic-based prepreg was determined. In this context,we did further research and found out the best condition on rapid analysis at a higher temperature, where part of the curing reaction could happen.The condition on accurate analysis for phenolic-based prepreg is: the condition of temperature for testing volatiles content is 80 ℃, holding time is 80 min. The condition on rapid analysis is: the condition of temperature for testing volatiles content is 110℃, holding time is 15 min. And it is concluded that the phenolic-based of prepreg volatile content test condition does not relate with the varieties of the substrate.

STUDYING ON HYDRAULIC PRESSURE FATIGUE PROPERTIES OF STEEL PIPE CONTAINING DEFECTS WITH FIBER COMPOSITE REINFORCING

XIAO Hong-bo, CAI Hao-peng

2015, 0(6): 84-87.

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In order to evaluate pipeline reinforcing effect with glass fiber composite material, cylinder tube with thinned defects was prepared. The test results showed that the defect area determined the reinforcing area of composite materials. As the border width of reinforcing composite materials is more than 80% of the defect of the axial length, the composite performance was fully played when pipeline blasting. Through reasonable design, the short-time burst pressure of reinforcing steel tube was more than 30MPa. At that time, the fatigue number of composite reinforcing steel pipe was greater than 15000 times.

ADHESIVELY BONDED REPAIR OF DAMAGED METALLIC STRUCTURE USING UV CURABLE CARBON FIBER FABRIC/CEP-ES RESIN COMPOSITES

ZHAO Pei-zhong, WEI Hua-kai, HUANG Xu-ren, DAI Jing-tao

2015, 0(6): 88-92.

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The UV ignited self-propagating curing resin blends, including cycloaliphatic epoxy (CEP) and organic silicone resin modified by epoxy (ES), were designed. Based on the blends, carbon fiber fabric reinforced composites can be cured quickly by UV radiation. Adhesively bonded repair of damaged metallic structure using UV curable carbon fiber composite material was studied experimentally. According to the results, the introduction of ES can not only increase the load bearing capability of adhesively repaired structure but also improve its resistance of hydrothermal environment. When the weight percent of ES was 20%~30%, the repaired structure had the best ability of load bearing. Increase of the length and layer number of composite patch can enhance the repair effect. Compared with single-sided repair, double-sided repair was the better repair mode.

EXPERIMENTAL STUDY ON THE DURABILITY OF GFRP PIPE CONCRETE COLUMNS UNDER WET AND DRY CYCLES IN SALT SOLUTION

LV Zhen-ying, SHAN Lu-yang

2015, 0(6): 93-96.

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Eleven columns consisting of six plain concrete and five GFRP pipe concrete columns are tested in the paper under axial compression load in the salt solution of different wet-dry cycles environment. The experiment is focused on the analyses of ultimate strengths and strains of the specimens. It is to analyze the effects on the plain concrete columns and the GFRP pipe concrete columns under the salt solution environment and different wet-dry circles, respectively. The experimental results show that, whether at room temperature or in the salt solution corrosive environments, the strength, stiffness and ductility of GFRP pipe concrete columns have different degrees of increase relative to those of in plain concrete columns. With the increase of wet-dry cycles in the salt solution, the clamping band effect of GFRP pipe to the core concrete, which helps increasing the strength, stiffness and ductility of the GFRP pipe concrete columns, have a certain degree of reduction as compared to those at room temperature.

PROGRESS IN FIBRE VARIABLE ANGLE TOW PLACEMENT TECHNOLOGY

DENG Yuan, LIU Dong, ZHU Ying-dan, HUANG Bin

2015, 0(6): 97-100.

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Fiber Variable Angle Tow placement (VAT) is a new advanced technology which is capable of steering individual curvilinear fibers through the ply. This paper introduces the concept of VAT technique and its curvilinear fiber trajectories, and highlights traditional fiber path design methods. Furthermore, the potential applications of VAT technique in different areas are analyzed.

Industry information contents

2015, 0(6): 101-128.

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