COMPOSITES SCIENCE AND ENGINEERING

STUDY ON HYGROTHERMAL AGEING OF PMI FOAM CORED SANDWICH COMPOSITE

YIN Liang, ZHENG Guo-dong, DING Chang-fang, ZHU Yuan-zhe

2015, 0(8): 5-9.

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An experimental study was performed to investigate the hygrothermal ageing mechanisms of PMI foam cored sandwich composite. To determine the effects of marine environment on the properties of sandwich composites. The polymethacrylimide (PMI) foam cored sandwich structure was prepared by using PMI foam, E-glass/epoxy resin (SW110C/608) composite panel. The moisture absorption of PMI foam cored sandwich structure, composite panel and PMI foam were investigated, and the effect of the hydrothermal condition on the compressive and flexural properties of the PMI foam cored sandwich structure was also determined. The results indicate that the saturated hygroscopic time of PMI foam cored sandwich structure is 30 days and its absorption ratio is 4.08%. The absorption behavior follows Fickian diffusion behavior and the diffusion constant for foam is about 30 times greater than those for the composite panel. Due to concentration gradient and the plasticization of water, the decrease of flatwise compression strength, edgewise compression strength and flexural strength is 32.86%, 16.73% and 23.94%, respectively.

THE STUDY OF THE SPECIFIC DYNAMIC ELASTIC PROPERTY OF COMPOSITE GUQIN

XU Zhen-yu, YU Yang

2015, 0(8): 10-13.

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We choose the specific dynamic elastic modulus as an index to judge the dynamic behavior of material. In this article, we conducted the experiment to study the specific dynamic elastic modulus of the faceplate and baseplate of composite Guqin with different plies and compared with wooden Guqin. From the results, we can get the specific plies which are in agreement with wooden Guqin in dynamic behavior. It demonstrated the feasibility of using composite materials to make Guqin, and provided a basis of studying the sound characteristics of composite materials.

DAMAGE IDENTIFICATION OF EULER-BERNOULLI FUNCTIONALLY GRADED BEAM BY THE MODAL STRAIN ENERGY CHANGE RATIO METHOD

HUANG Li-xin, YANG Zhen-zhen, ZHAO Wen-ju

2015, 0(8): 14-17.

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A damage identification method based on modal strain energy is presented for an Euler-Bernoulli functionally graded beam. The finite element method is employed to compute the elemental stiffness matrix and the modal parameters such as mode shapes of the beam. The elemental modal strain energy, which is defined as the product of the elemental stiffness matrix and the second power of the mode shape component, is calculated by using the finite element method results. On this basis, the damage indicator for the Euler-Bernoulli functionally graded beam is developed by way of the change of the modal strain energy in each element before and after the occurrence of damage. A numerical example is given to illustrate the validity of the proposed method for the damage identification of the Euler-Bernoulli functionally graded beam. Numerical results show that the damaged element can be easily identified by using the damage indicator.

NUMERICAL ANALYSIS ON LOAD-DEFLECTION OF PVC-FRP CONFINED REINFORCED CONCRETE COLUMNS UNDER ECCENTRIC COMPRESSION

YU Feng, LI De-guang, XU Guo-shi, WANG Xu-liang

2015, 0(8): 18-24.

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To predict the whole process analysis of load-deflection relationship of PVC-FRP confined reinforced concrete columns under eccentric compression,a nonlinear program is developed by using fiber model method, and then the correctness of the calculation program is verified. Based on the program, the effect of major factors on the mechanical behavior of PVC-FRP confined reinforced concrete columns are analyzed. The influence law of the hoop spacing of FRP strips, eccentricity, the width of FRP strips, concrete strength and reinforcement ratio on the load-deflection relationship are obtained. This paper lays foundation for the analysis of PVC-FRP confined concrete column under complex stress state.

EXPERIMENTAL STUDY ON SHEAR FATIGUE PERFORMANCE OF COMPOSITE PRE-TIGHTENING TOOTH CONNECTOR

GAO Jian-gang , LIU Peng-fei , ZHAO Qi-lin, LIU Jin-chun (1.Sate Key Laboratory of Disaster Prevention & Mitigation of Explosion & Impact, PLA University of Science and Technology, Nanjing 210007,China; 2.College of Corps of Engineering, PLA University of Science and Technology, Nanjing 210007, China)

2015, 0(8): 25-30.

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Previous study shows that composite pre-tightening tooth connector has a good static performance, but the fatigue performance under cyclic loading had never been deeply investigated. This article conducted a lot of fatigue tests under different pre-tightening force. First of all, through the analysis of experimental results, the effect on fatigue life of pre-tightening was discussed. Then, the changing rule of the hysteresis curves was analyzed, and the relationship between hysteretic curve and the fatigue damage accumulation was discussed. At last, based on the observation and analysis of the specimen fatigue fracture, the fatigue failure mechanism of pre-tightening tooth connector was explored.

MATHEMATICAL METHOD FOR DESIGN OF LAMINATE FOR RADOME

QU Xiu-xiao, LI Xing-de, ZHOU Chun-ping

2015, 0(8): 31-35.

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The design of layup angles in the laminate of the radome is directly related to the overall safety of the structure. Modern commercial software can conduct simulation analysis relying on the predefined layer designs. These predefined layer angles could be designed specific to the particular mesh and models, but this kind of layer design lacks the flexibility and the versatility. This paper uses the geometrical theory and design programs to transfer the longitudinal and latitudinal directions of planar woven fabric on the three dimensional surfaces of the radome to make layer angle designs of the woven glass fabric, and to project the directions onto the models of the finite element model to determine the angles relative to the every specific element. The methodologies in this paper endows the layer design with an obvious and versatile process. It also adds the flexibility of the layer angle calculation and breaks the reliance on different software.

INFLUENCE OF COMPOSITE CROSS ARM STRUCTURE PARAMETERS ON BOND STRESS

ZHAO Hua-yun, YU Jie, QIU Yong

2015, 0(8): 36-40.

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Joint reliability of composite cross arm for power transmission tower is investigated. A simplified mechanical model of composite cross arm is established and the generation mechanism of bond stress and failure reasons of joint are discussed. The relationship between the length of composite cross arm, the inner diameter of FRP(fiber reinforced plastics)tube, the thickness of FRP tube, the height of metal sleeve and the thickness of metal sleeve is obtained by simulation analysis based on ABAQUS, which is of reference value for the design and optimization of composite cross arm.

DETERMINATION OF STRUCTURAL PARAMETERS OF GLASS FIBER RESIN COMPOSITES AND THEIR INFLUENCIAL FACTORS

SHU Ming-jie, ZU Lei, WANG Ji-hui, LI Shu-xin

2015, 0(8): 41-46.

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Compared to traditionally-used metal materials, the structural parameters of glass fiber reinforced polymer (GFRP) composites have a large variation. The design parameters taken from the average values obtained from the structural test are thus not reliable. Therefore, investigations on mechanical properties of GFRP composites became increasingly important in their structural design. The strength values treated using statistical data should be used for design. The goal of this paper was to give a brief overview of the two methods for calculating A/B-basis values of GFRP composites, and to compare the accuracy of the two methods. The influential factors which affect the structural parameters of GFRP composites were also elaborated. The results show that the accuracy of the A/B-basis values improves with increasing the sample size; the use of the normal distribution leads to higher B-basis values than the use of the Weibull distribution. In addition, the conservation rate of the B-basis values reduces as the coefficient of variation of the samples becomes larger.

TRIAL PRODUCTION AND PERFORMANCE STUDY OF COMPOSITE MATERIAL UNDERPAN OF AIR CONDITION

YAN Meng-xue

2015, 0(8): 47-50.

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Nowadays, most of underpan of air condition is made of galvanized steel sheet, which has the disadvantages of corrosive rust and big noise. To solve this problem, the idea of using composite material instead of galvanized steel sheet for the underpan of air condition was proposed in this paper. The sample was made of glass-fiber reinforced phenolic composites and fibre-glass reinforced polyester, respectively. The properties of samples were tested and the test results proved that this scheme is feasible. The bending strength, bending modulus and the tensile strength of the sample made of glass fiber reinforced phenolic reaches 302.19MPa, 25.53GPa and 102.95MPa, respectively. At last, the products also passed the load test.

STUDY ON INTERFACE PERFORMANCE IN BAMBOO REINFORCED COMPOSITES

LI Hong-bin, LI Wei, DONG Lu-lu

2015, 0(8): 51-54.

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In this paper, with bamboo as a reinforcing material, the effects of chemical modification by alkali treatment and silane coupling agent treatment on tensile strength of bamboo and interface shear strength of bamboo reinforced composites were investigated and the failure mode of impact section of unidirectional composites was analyzed. The experimental results show that appropriate concentration of alkali treatment modification methods was better than the KH550 on the tensile strength of bamboo and interface shear strength of bamboo composites. But, the double modification has a better improvement effect. The failure mode of impact section is bamboo fiber pull-out fracture, matrix crack, fiber/matrix interfacial debonding. And, shear layer was found by SEM in unidirectional composites and the interface performance has been improved.

THE APPLICATION OF FRP FLUE DESIGNING BASED ON ANSYS SECONDARY DEVELOPMENT

HE Xue,DENG Jing-lan,LUO Shu-qing,WANG Ji-hui

2015, 0(8): 55-58.

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In this paper, secondary development of ANSYS is made by APDL, and VB is used to design the interface of FRP flue. Using VB interface, we only need to input related parameters, so we can quickly achieve parameterized modeling of FRP flue, calculation and post-processing. With the aid of the secondary development, designing cycle of the FRP flue can be greatly shortened. Besides, the development of design efficiency is raised availably.

A STUDY COMPARING ISOPHTHALIC AND TEREPHTHALIC BASED POLYMERS IN GASOLINE/ALCOHOL AND FUEL C/ALCOHOL MIXTURES

JIN Li-xin, PENG Ji-mei, YU Hao, LV Jin-yan

2015, 0(8): 59-65.

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This paper explores isophthalic acid and terephthalic acid based unsaturated polyester resins and the role of reduced styrene content (VOC) on the corrosion performance in gasoline/alcohol and reference fuel C/alcohol mixtures. Various studies conducted with ASTM C581 and UL1316 test methods conclude that the terephthalic resins provide superior performance over isophthalic resins. A new low styrene TPA based resin meets the "All Fuels" requirement of UL1316.

STUDY ON THE PRETREATMENT PROCESS OF ADVANCED PULTRUSION FOR HALF LENTICULAR TUBE

ZHOU Huang-he, QI Jun-wei, ZHU Jing, LI Tao

2015, 0(8): 66-70.

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To decrease the defects such as fiber distortion and insufficient thickness on both sides of the half lenticular tube, pretreatment process was proposed by analyzing the shortcoming of the existed advanced pultrusion process. The temperature and time of pretreatment were stydied with an oven and a hot-pressing device, the axial tensile property and interlayer tensile property were carried out to analyze the effects on the samples. The result showed suitable parameters for pretreatment process were 100℃ for 50min, 105℃ for 40min, 110℃ for 25min; the mechanical properties of the product didn't decrease with pretreatment process; the lower the pretreat temperature was, the better mechanical property the sample could reach.

EXPERIMENTAL STUDY ON BOND BEHAVIOR OF GFRP REBARS AND RUBBERIZED CONCRETE

ZHANG Wei-dong, WANG Zhen-bo, HE Wei-zhong

2015, 0(8): 71-74.

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Based on the pull-out tests of 15 groups specimens according to CSA standard, the influence of the diameter of GFRP rebars,the incorporation rate of rubber and cubic compressive strength on bond behavior of GFRP rebars and rubberized concrete were studied. The test results show that the failure mode of mostly specimens are pull-out failure; the diameter of GFRP rebars,the incorporation rate of rubber and cubic compressive strength all have influences on the bond behavior of GFRP-rubberized concrete, and the bond performance decreases with the increase of the diameter of GFRP rebars and the incorporation rate of rubber, and increase with the cubic compressive strength of the increase of GFRP-rubberized concrete.

EXPERIMENTAL STUDY ON THE DURABILITY OF GFRP BARS EMBEDDED IN ACTUAL CONCRETE ENVIRONMENT

DAI Li, HE Xiong-jun, YANG Wen-rui, HE You-wei

2015, 0(8): 75-79.

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An experimental study on GFRP bars embedded in concrete environment was conducted to investigate their tensile strengths. The degradation mechanism of GFRP bars exposed to tap water and alkaline solution at different temperature was studied by analyzing the ultimate tensile strength, elastic modulus of the specimen. The results showed that after being exposed to tap water environment for 90 day at 20 and 40℃,tensile strength of GFRP bar decreased by 8.8%, 12.2%, respectively, but the retention can reach to 17.5%, 22.1%, respectively, in the alkaline solution at the same temperature. With the increase of exposure time, the decrease of tensile strength gradually slows down. Through comparing the specimens embedded in concrete environment with specimen directly immersed in alkaline solution, we can find out that the tensile strength degradation rate of GFRP bar under simulated alkaline solution is about 2.5~3 times of the actual concrete environment.

THE DEVELOPMENT OF EXPANDING TECHNOLOGY FOR HIGH-PERFORMANCE YARN

ZHONG Wen-xin, MA Pi-bo

2015, 0(8): 80-85.

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This article introduces the definition of expanding fiber and the influence on the form of the high-performance fibers, fiber permeability and performance of composite, and calculates the width of expanding the fiber bundle and describes contrastly five kinds of common methods of expanding fiber at present, such as hot rolling, mechanical methods and ultrasonic wave. We explain the equipments and theories of these five expanding fiber methods and the prospect for expanding fiber.

DEVELOPMENT STATUS AND OUTLOOK FOR CHINA COOLING EQUIPMENT INDUSTRY IN 2014

YIN Zheng, ZHANG Wen-ling

2015, 0(8): 86-92.

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This paper makes a comprehensive description about the development status of China cooling equipment industry in 2014, makes an objective summary and conclusion about problems faced in the current industry development, and come up with some views and opinions about the development tendency.

"INDUSTRY 4" AND THE COMPOSITE INDUSTRY DEVELOPMENT

ZHANG Lin-wen

2015, 0(8): 93-95.

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