COMPOSITES SCIENCE AND ENGINEERING

SRUCTURE DESIGN AND ANALYSIS OF CARBON FIBER COMPOSITE DRIVE SHAFT FOR AUTOMOBILE

MA Xiang-yu, ZHANG Jin-guang, CAI Guang-sheng, TAN Jian

2017, 0(8): 5-9.

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Carbon fiber composite material has characteristics of light weight, high specific modulus, high specific strength and fatigue resistance. According to the requirements of strength and critical speed, a carbon fiber composite drive shaft which was applied in one type of automobile was designed. The finite element analysis software Abaqus was used to simulate the drive shaft, and the results show the stress, strain and failure distribution of the shaft under torque load. There has average stress and strain distribution in the carbon fiber shaft tube, and the simulation results are in agreement with the design theory and experiment. The mechanical properties of carbon fiber composite drive shaft meet the requirements in automobile.

STUDY ON THE INFLUENCE OF ABSORBING BOUNDARY TO THE PROPAGATION OF LAMB WAVE IN COMPOSITE MATERIALS

SONG Cheng-jie, ZHENG Yan-ping, JI Zhi-xing, ZHAO Zhu-jun

2017, 0(8): 10-14.

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When carrying out structural health monitoring on complex structures using Lamb wave, the finite element simulation of Lamb wave propagation process is usually performed. However, because of the size of the model, composite anisotropy and other reasons, much boundary reflected wave will produce and cover the damage waveform. Therefore, it is very important to establish the absorbing boundary to inhibit the influence of the reflected wave. This paper applies an absorbing boundary that incorporates Combin14 spring damper elements. The influence of several parameters to the absorption are studied. The parameters include the length of the absorbing boundary, the frequency, the direction of Combin14 element. And the results are compared with the traditional damping increasing absorbing boundary. The study indicates that both of the frequency and the length of the absorbing boundary have no effect on the absorbing effect of the absorbing boundary, but the wave-absorbing boundary length must be larger than that of wavelength to achieve the best absorbing effect. When the Combin14 elements are set in the direction of wave propagation, the absorbing effect will be best. Compared with the increasing damp absorbing boundary, the simulation time-consuming of the spring damper absorbing boundary obviously cut back and the absorbing effect is better in the low frequency band.

STUDY ON VIBRATION PERFORMANCE AND DAMAGING DETECTION OF COMPOSITE MATERIALS BASED ON FBG

ZHANG Chun-feng, WEN Xiao-yan, ZHANG Dong-sheng, CHEN Xiao

2017, 0(8): 15-19.

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In this paper, the vibration performance and damage types of carbon fiber composite materials were investigated based on FBG sensing technology. The free end of a carbon fiber composite cantilever beam was hit by a falling ball to generate a resonance in the cantilever. The resonance frequency was measured and the damping loss factor was calculated based on the vibration characteristic of the carbon fiber composite. Then, a man-made damage (a small hole) was introduced into the cantilever and the resonance frequency was measured again. The result was compared with the frequency without damage, so that the damage type could be judged. Finally, the results of the research will provide a reference to the study of the vibration performance and damage monitoring of carbon fiber composite materials.

EXPERIMENTAL STUDY OF FRP-STRENGTHENED RECTANGULAR CONCRETE AS AFFECTED BY ASPECT RATIO

YANG Zhi-gang, LI Xiao-xia, LIU Cheng-qiang

2017, 0(8): 20-24.

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Sixteen concrete columns which is strengthened with FRP sheets were fabricated and studied. The specimens were divided into four groups according to the aspect ratio. One is a control column which is unreinforced, two columns are reinforced by full wrapping with FRP sheet, and one is reinforced by partial wrapping with FRP sheet. The failure mode, bearing capacity and ductility of columns were studied by considering the changes of aspect, the type of the FRP and reinforcement. It was shown that the aspect ratio showed obvious influence on the obtained capability ductility, but had a weak influence on the ductility. The formula recommended by the code for strengthening concrete is verified. According to the test data, a modified model is suggested about the column reinforced by partial wrapping with FRP sheet.

EXPERIMENTAL STUDY FOR EVOLUTION BEHAVIOR OF COMPOSITE MATERIALS WITH DELAMINATION DEFECT BY FOUR-POINT BENDING

HAO Min-juan, XIE Zhong-peng, YUE Zhong

2017, 0(8): 25-29.

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In order to investigate the effects of stratified evolution and delamination on the load capacity and service life of the composite materials under the four-point bending load, the artificial tectonic defects of the different positions were set up. The four-point bending test was carried out, the whole process was recorded by acoustic emission, and the degree of damage for the composite material was judged by the collision accumulation-time-amplitude history diagram, load-time-relative energy history diagram, acoustic emission impact signal location diagram and so on. The results show that the stratification defects near the surface of the specimen accelerate the process of material failure and expansion. The location of the delamination defect changes the bending performance of the composites to a great extent. The closer the stratification defects are to the surface of the specimen, the greater the damage, the worse the service capacity of the specimen.

COHESIVE ZONE MODELS OF RESIN CONCRETE/STEEL INTERFACE SHEAR

CHEN Guang, HUANG Li, ZHOU Xin-wei, ZHENG Li-xia

2017, 0(8): 30-35.

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In this paper, a method of obtaining the interface shear cohesion model by the pull shear test combined with the finite element method is presented, and the feasibility of the method is verified from the energy release rate. The load-loading displacement diagram of the interface was obtained by the uniaxial shear test of the resin/concrete bonded specimen. Based on the bilinear cohesive shear model, the characteristic of the interfacial cohesion model was obtained by analyzing the shear process. The maximum stress and the characteristic displacement of the interface cohesion model are obtained by the finite element simulation. Finally, the energy release rate and the calculated energy release of the shear test are compared. The rate, the relative error between the two is within 10%, suggesting that the method of calculating cohesion is feasible.

THE WHOLE PROCESS ANALYSIS OF DAMAGE AREA EXPANSION OF COMPOSITE LAMINATES

CHEN Xing-jie, ZHOU Shi-gang, GONG Zhan-feng, LUO Teng-teng

2017, 0(8): 36-41.

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Two groups of quasi-static indentation tests were carried out on carbon fiber NCF laminates. In the first group, the influence of different head diameter on the damage area was studied by using different indenter sizes. In the second group, the repeated test of fixed head size was carried out to study the relationship between the static indentation force, the dent depth and the damage area by using the non-contact air-coupled ultrasonic scanning sample. Based on the Hashin criterion and the cohesive element, the whole process damage propagation analysis of the second groups of laminates was carried out by using Abaqus software. The results indicate that the tensile failure of matrix is the most easily damaged, and the damage area covers the other 4 kinds of damage areas. There is a connection between dent depth and damage area. At the beginning of the test, the dent depth increases slowly, the damage area increases fast; close to the ultimate load, the dent depth increases fast, the damage area increases slowly.

STUDY ON VIBRATION CHARACTERISTICS OF UNCONSTRAINED STAND-OFF LAYER DAMPING STRUCTURE CONSIDERING EFFECT OF ADHESIVE LAYER

YI Shao-qiang, HE Shi-ping, WANG Jie

2017, 0(8): 42-47.

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Considering the effect of adhesive layer on the stress and strain in unconstrained stand-off layer damping structure, adhesive layer is equivalent to the isotropic material. The joint simulation method of ANSYS and MATLAB is used to analyze the vibration characteristics of unconstrained stand-off layer damping structure with adhesive layer with adhesive layer parameters. The results obtained by modal strain energy method and control variable method show that the adhesive layer plays a key role in the structural vibration characteristics. Therefore, the choice of adhesive laying unconstrained stand-off layer damping structure should ensure that adhesive layer has good mechanical environment under the premise of choice to meet the best properties of adhesive layer of adhesive products.

FINITE ELEMENT ANALYSIS ON ANISOTROPY OF 3D COMPOSITE UNIT-CELL MODEL

FENG Gu-yu, CAO Hai-jian, ZHOU Hong-tao, LU Xue-feng

2017, 0(8): 48-52.

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3D composite unit-cell model was created by PRO/E 5.0 mapping software. Compressive property of unit-cell model under multipronged compressive loading were simulated with the help of the finite element software ANSYS. The stress distribution of the unit-cell model was investigated and analyzed. Meanwhile, taking the unit-cell model subjected to compressive loading in X direction for example, the stress distribution of fibers and resin matrix was analyzed. The results showed that 3D composite was obviously anisotropic under compressive loading,manifesting as the best compressive property in X direction and the worst compressive property in Z direction. Fibers made the major contribution to subject the compressive loading, while the resin matrix made the minor contribution to subject the compressive loading.

DAMAGE DEFORMATION MEASUREMENT AND ACOUSTIC EMISSION MONITORING OF WAVES IN COMPOSITE MATERIALS

ZHAO Wen-zheng, ZHANG Yan-nan, LUO Xin-yu, Pang Yan-rong

2017, 0(8): 53-60.

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In the compression tests of glass fiber composite materials which have waves, the damage evolution of glass fiber composites was studied by using the acoustic emission (AE) and digital image correlation (DIC) method. The relationship between compressive mechanical response behavior of composite materials and damage deformation field information or acoustic emission characteristic parameters was analyzed by collecting acoustic emission signals and damage deformation field information during compression test. The results show that waves have serious influence to mechanical property of composite materials. By analyzing acoustic emission signals, it is found that, as waves' ratio of width and height decrease, mechanical property of composite materials becomes worse; and in the same ratio of width and height, as waves' height increase, mechanical property of composite materials is worse. By analyzing strain field and displacement field from DIC, it is found that, in the same load increment, the maximum strain increase and the composite materials which have a wave with higher ratio of width and height have a larger increment of maximum strain. The place which is close to the middle of composite materials has a larger horizontal displacement. However, loading direction displacement is related to creak. The place which is close to creak has a larger loading direction displacement. It reflects clearly damage and deformation characteristic of composite materials by using displacement field and strain field.

EXPERIMENTAL STUDY ON THE DURABILITY OF BFRP BARS UNDER THE ENVIRONMENT OF ALKALINE SOLUTION, ULTRAVIOLET LIGHT AND THEIR CROSS CORROSION

WANG Hai-liang, LI Chang-kun, GUO Fu

2017, 0(8): 61-68.

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In order to study the effects of diameter and corrosion environment on the tensile properties of BFRP bars,the tensile mechanical tests of three kinds of BFRP bar specimens with different diameters (6 mm, 8 mm, 10 mm) were carried out under the natural environment, alkaline solution soaking (pH=10), ultraviolet irradiation (irradiance is 550 W/m²) and their cross corrosion environment, and scanning electron microscopy (SEM) images were used to evaluate the microstructure of BFRP bars after the fracture, and the test results were analyzed. The main conclusions are as follows: under three different environmental conditions, with the corrosion time increasing, the tensile strength of BFRP bars decreases and the degradation rate decreased gradually; the fluctuation of the elastic modulus of BFRP bars is less than 5%, but not obviously; the trend of tensile strength and elongation at break is largely the same; under the ultraviolet irradiation environment the tensile strength of BFRP bars shows the phenomenon of degradation and incomplete recovery;under the cross corrosion environment, that of 6 mm and 8 mm diameter BFRP bars shows the same law, but the 10 mm diameter BFRP bars has not. Based on the durability decay rate defined in this paper, the researchers finds that the effect of alkaline solution soaking on the durability of BFRP bars with diameters of 6 mm and 8 mm is all the largest, and that of cross corrosion environment is moderate, and that of ultraviolet irradiation environment is the least; the effect of cross corrosion environment on the durability of BFRP bars with diameters of 10 mm is the largest, and that of alkaline solution soaking is moderate, and that of ultraviolet irradiation is the least; under three different environments, the durability decay rate of 6 mm diameter BFRP bars is all the biggest, and that of 10 mm diameter BFRP bars is all the smallest.

STUDY ON THE EFFECT OF ADHESIVE PROPERTIES ON CRACKED STEEL PLATES REINFORCED BY CFRP

WU Jian, ZHANG Tong-tong, LI Hong-yun, WANG Wei-bo

2017, 0(8): 69-75.

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Steel structure with crack used in marine engineering is the object of study. Tensile properties of steel plates reinforced by CFRP is simulated by the model established with virtual fracture closure method. The influence of shear strength and elongation of the adhesive on the reinforcement was analyzed and compared. The effect of marine environment factors such as alternating hot and humid, salt mist and strong solar radiation is studied by model test. The reinforcement program is optimized through using marine-resistant adhesive. The results show that the properties of adhesive has little effect on the yield point of reinforcement structure, but it can influence the ultimate capacity obviously. The performance of adhesive can be decreased by environment factors. Reliability and durability of reinforcement can be improved by using marine-resistant and excellent adhesive.

EXPERIMENTAL STUDY OF THE SHEAR PERFORMANCE OF BFRP-REINFORCED RAC BEAMS WITHOUT STIRRUPS

HAN Ding-jie, LIU Hua-xin, ZHANG Zhi-jin, PENG Chang-ling

2017, 0(8): 76-82.

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According to the shear tests of 4 basalt fiber reinforced polymer (BFRP) reinforced recycled aggregate concrete (RAC) beams without stirrups and 4 recycled concrete beams without stirrups, the failure modes and cracking patterns for recycled concrete beams of which recycled coarse aggregate replacement ratio for 100% were observed. The influence of shear span ratio, reinforcement ratio, and concrete compressive strength on the cracking load, ultimate bearing capacity and deflection of the beams with different types of longitudinal reinforcement were also analyzed. The test results were compared with shear design equations of the GB 50608—2010, the ACI-440.1R-06 and the CSA.S 806-12 guidelines. The results indicate that the behavior of recycled concrete beam is similar to that of ordinary concrete beam, yet the crack propagation and crack width are faster and wider for recycled concrete beams reinforced with BFRP bars. And, shear design equations of the ACI-440.1R-06 and the CSA.S 806-12 codes provided quite close predictions. However, the predictions of GB 50608—2010 were over-conservative.

RESEARCH ON 2 MW COMPOSITE NACELLE STRUCTURE OPTIMIZATION

ZHANG Jian-min, WANG Ya-peng, ZHAO Min-min

2017, 0(8): 83-87.

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Due to the anisotropy, compares to metal materials, GFRP composite can performance its advantages better by corresponding design. Composite nacelle is a typical example, the most structure analysis of it is only to check its bearing capacity. According to the Lloyd's GL2010 standard, the model was built by commercial soft SolidWorks, the stiffness and strength are calculated by finite element soft ANSYS. On the basis of the results, the design of the reinforced rib size and the skin thickness are optimized. Limiting condition of manufacture, location of stiffeners, block, cost and other requirements are all in the considering. The structure after optimized was analyzed, and the results show that the analysis and optimization result based on the manufacture, meets the engineering requirements for stiffness more, this worth to be recommended.

EXPERIMENTAL STUDY ON DAMAGE RESISTANCE AND DAMAGE TOLERANCE OF COMPOSITE LAMINATES SUBJECTED TO QUASI-STATIC INDENTATION

ZHANG Wei, LI Wen-xiao, WAN Chun-hua

2017, 0(8): 88-91.

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According to the standard test method, damage resistance and damage tolerance of composite laminates subjected to quasi-static indentation are studied. Test data such as contact force, indentation depth and indenter displacement are obtained and compressive residual strength of damaged laminates are tested. The relationship between indentation depth vs contact force and residual compressive strength vs indentation depth are studied, damage process subjected to quasi-static indentation and failure pattern under compression are also discussed. The results reveal that initial damage occurs when barely visible indentation can be seen on the surface of laminates. Indentation depth augments obviously as the contact force increases, while the residual compressive strength descends rapidly with the increasing of indentation depth. When the contact force reaches to the maximum value, load-carrying capacity has lost, and large amount of fiber breakage can be seen on the back surface. For laminates with the quasi-static indentation damage, compressive failure pattern is laminates fracture through the damage zone.

STUDY ON ADHESIVE PROPERTIES OF TWO KINDS OF EPOXY CONSTRUCTION ADHESIVE USED FOR OFFSHORE WIND TURBINE BLADES

WU Hai-liang

2017, 0(8): 92-96.

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The development and treng of offshore wind power at home and abroad are briefly introduced. At the same time. The rheological and exothermic characteristics, the glass transition temperature, mechanical properties and salt water resistance of two representative epoxy structural adhesives are tested by means of rheometer, universal testing machine and DSC. The test results show that these two kinds of adhesive extend similar performance, and both meet the requirements of international standard IEC 6140023 "wind turbine rotor blade full size proportional structure test", the national standard GB/T 25383—2010 "Wind Turbine Blade", and they also meet the durability and General technical requirement that the design life can't be less than 20 years regulated by material technical specifications of the wind turbine blades of the German Lloyd's Register (GL).

RESEARCH ON RHEOLOGICAL PROPERTIES AND CURING PERFORMANCE OF EPOXY RESIN BY RTM

ZHU Xiu-di, WANG Li-jie, SUN Chao-ming, PENG Fei

2017, 0(8): 97-101.

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Two kinds of epoxy resin systems R2511 and R2512 were prepared to obtain the appropriate system for carbon fiber reinforced composites. The processing property, curing characteristics and mechanical property of the composites by using RTM molding has been investigated thoroughly. The results show that the two kinds of systems own the good operating window with low viscosity. The optimum operating temperature of R2511 system using RTM ranged between 40 ℃and 50 ℃, while the room temperature was more suitable for R2512. The activation energy of R2511's 72 kJ/mol, while R2512 have the lower value 62 kJ/mol. As to the overall mechanical property of composites, R2512 was also superior to R2511 system. Therefore, the two kinds of resin are suitable for epoxy resin systems with different operating temperature.

DEVELOPMENT OF THEORETICAL RESEARCH OF 2D BRAIDED

ZHANG Shuang , WU Xiao-qing, CHENG Yong

2017, 0(8): 102-109.

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The paper discusses the progress of research on 2D braiding technology from perspectives of kinematic method and finite element method. On other hand, it summarizes the research process of yarns hypothesizing sectional ellipse, lenticular shape and flat hexagon. It also concludes the research on unit cells with 2D biaxial braided structures and triaxial braided structures. Lastly, the paper proposes suggestions on relevant issues to be considered in research concerning unit cells.

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