COMPOSITES SCIENCE AND ENGINEERING

RESEARCH OF THE ENGINEERING ESTIMATION METHOD ON LAUNCHING FAILURE OF THE UAV OF HONEYCOMB SANDWICH

ZHANG En-yang, LIU Bo, LU Zhen-yu, FENG Kun-cheng

2015, 0(9): 5-10.

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The composite honeycomb sandwich is widely used for the airframe of small UAV, and the design of honeycomb sandwich is needed to meet the requirements of UAV technology evolving. Aiming at the launching test of small UAV, we analyze the modeling and the engineering estimate based on the classical beam bending theory and the basic assumption of thin panel which is based on the shear theory of Reissner, and compare with the results of finite element. The results show that the eviation of the maximum stress on the top panel is 3% and the eviation of the maximum stress on the bottom panel is 10.8%, and the results are consistent with the destruction of launching test. The result shows that the method of engineering estimate has certain guiding significance for the actual design of honeycomb sandwich.

THE EXPERIMENTAL RESEARCH FOR DESIGN ALLOWABLE OF TENSION STRENGTH OF SW220/430LV COMPOSITE MATERIAL

CHEN Guo-tao, MEI Zhi-yuan, LI Hua-dong

2015, 0(9): 11-16.

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The tensile strength design value is an important guideline to weigh the intensity of composite laminates. SW220/430LV composite material is a kind of typical composite material widely used in warships. In order to explore the intensity, the paper carried out the investigation about the tension strength of 0°/90° with referring to GB/T 1447-2005, and worked out tensile strength X_T by B-base value. Then, we get loads responsible to reduction coefficient to make research about tension-shear fatigue and the left stiffness, shear strength, and explore effects of the load characteristics, such as stress ratio, frequency, fatigue cycle to the SW220/430LV composite material at the same time. According to our research, we take 0.45 X_T as the design tensile strength design value for SW220/430LV composite material, when allowing for mechanical fatigue.

COMPUTATIONAL MODEL OF WIND TURBINE BLADES DE-ICING POWER DENSITY BASED ON POLYMER ELECTRIC HEATING FILM

NI Ai-qing , WANG Yan-ming, WANG Ji-hui, MU Shu-xiang

2015, 0(9): 17-23.

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In this paper, a heating power density computational model, based on melting ice interface displacement and phase change heat transfer theory, is established for wind turbine blade de-icing system using polymer electric thermal film. This model takes in account the thermal storage of GFRP layers and ice, interface melting ice latent heat and convection heat transfer, convective mass transfer and radiation heat transfer of air exchange with the surrounding environment. In order to verify the proposed model, the heating power density under specific environment was calculated and the corresponding deicing experiments using GFRP plates containing polymer electric heating film were carried out. The results show good agreements between the mathematical model and experiment.

ACOUSTIC EMISSION MONITORING AND STRAIN ANALYSIS OF COMPOSITE MATERIALS EMBEDDED WITH DELAMINATION UNDER COMPRESSION LOAD

LV Zhi-hui, LIU Ran, WANG Ya-rui, ZHOU Wei

2015, 0(9): 24-28.

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For the study of the damage evolution and failure process of composite specimens embedded with circular delamination, for which the diameters were 5mm and 10mm, respectively, the uniaxial compression test, acoustic emission (AE) monitoring and strain measurement of unidirectional glass fiber/epoxy composites were conducted. The results show that the delamination growth and the failure mechanism of two kinds of specimens with different delamination were similar under compressive loading. The area of delamination has great influence on the bearing capacity of specimens. The larger area of delamination, the lower carrying capacity and the more serious damage of the specimen are obtained. The load-longitudinal strain curve changes from linear to approximate linear to nonlinear. The change process was coincided with the analysis results of AE signals.

EFFECT OF STITCHING ON ENERGY ABSORPTION PROPERTY OF CARBON FIBER BRAIDING COMPOSITE TUBES

ZHANG Qian-jin, YANG Yu-qiu, TADASHI Uozumi, MA Yan

2015, 0(9): 29-34.

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In this study, two kinds of carbon fiber braiding fabric including with and without stitching structure as reinforcement, epoxy resin as matrix were chosen to manufacture carbon fiber braiding composite tubes via transfer molding (RTM) method. The effects of stitching on energy absorption property and mechanical property of braiding composite tubes were investigated. To investigate the energy absorption property and mechanic property of these two kinds of braiding composite tubes, quasi-static compression tests were performed. It was found that stitching improved the energy absorption capacity and mechanical properties obviously. The specific energy absorption of the tube with stitch was 16% higher than the one without stitch. To research the energy absorption mechanisms, the tested tubes were cast in resin, cut, and polished in order to document the energy absorption mechanisms. It was found that the central crack was restrained by the stitching yarn in the stitched braided FRP tube during the crushing process. That is to say, the mechanical property in the thickness of braided tube composite was enhanced. With the effect control of the central crack by the stitching yarn, high energy absorption management could be obtained.

NON-DESTRUCTIVE INSPECTION METHOD FOR GLASS FIBER COMPOSITE BASED ON THz WAVE

LIAO Xiao-ling, LIU Yan-lei, WANG Hong, LI Wei-zhong

2015, 0(9): 35-38.

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There has been a series of significant advances and applications in terahertz (THz) technologies, terahertz (THz) wave with its perspectivity and safety was widely applied in the field of nondestructive testing. The unique properties help them become effective tools for non-destructive detection. With the increased utilization, the backward wave oscillator terahertz continuous wave imaging system was used to perform non-destructive testing of glass fiber composite material whose thickness is 5mm. Imaging and data of the sample within heat damage (d_min=0.5mm), air delamination (s_min=0.5mm²) was obtained. The results show that heat damage and delamination of glass fiber reinforced plastic (GFRP) reference sample was detected from the back side. Additionally, glass fiber reinforced plastic (GFRP) samples were evaluated with respect to the measurement of material properties, the attenuation caused by epoxy was proved to be insignificant, and the particular features of the defects in sample are recognized, benefiting to identify the defects.

UNIAXIAL AND BIAXIAL TEST AND FULL-FIELD 3D DEFORMATION ANALYSIS FOR A WIND TURBINE BLADE

HU Xue-bing, ZHOU Hua-fei, WANG Xiao-ping, QIN Liang-zhong

2015, 0(9): 39-46.

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A wind turbine blade was tested for the full-field 3D deformations under uniaxial and biaxial static loads by making use of digital image correlation technique. The results showed that the 3D displacements of the wind turbine blade are well distributed while the strains are not. Among the three displacements, the out-of-plane displacement is much larger than the in-plane displacement. The 3D displacements of the wind turbine blade induced by the biaxial loads differ significantly from their counterparts induced by uniaxial loads, and the differences increase as the load increases. In the full field of the wind turbine blade, the flapwise displacements under biaxial loading are greater than that under uniaxial loading of the same level. From the root up to 74% of the blade length (100cm), the edgewise displacements under dual-axis loading are larger than those under single-axis loading, while it is contrary in the rest part of the blade. The spanwise displacements generated by uniaxial and biaxial loading are almost 0 in the region of 0~41% of the blade length. In the rest region of the blade, the spanwise displacements under biaxial loading are greater than that under uniaxial loading of the same level.

EFFECTS OF FACE SHEET LAY-UP TO THE FOAM SANDWICH STRUCTURE SUBJECTED TO QUASI-STATIC INDENTATION

WEI Hao, ZHU Ling, WANG Ji-hui

2015, 0(9): 47-51.

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In this paper, we tested quasi-isotropic face sheet foam sandwich structures with different kinds of lay-up face sheet under quasi-static indentation (QSI) test. Through analyzing different specimens' energy absorption efficiency, failure mechanism and bottom face sheet failure deflection, we could conclude that woven roving specimens failed mainly by fiber breakage, while unidirectional woven roving specimens mainly in the form of delamination. However, specimens added woven roving to the surface of unidirectional woven roving or multi-axial fabric failure feature included both fiber breakage and delamination and with bigger energy absorption efficiency. Besides, the bottom face sheet failure deflection was restricted by the mechanical properties of face sheet and the whole structure, which had no straight relationship with the energy absorption efficiency.

REVERSE ALGORITHM FOR OUTER CONTOUR OF AIRCRAFT RADOME

LI Xing-de, ZHOU Chun-ping, ZHANG Li, QIU Jin-hao

2015, 0(9): 52-56.

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The design of broadband radomes often starts from aerodynamic contour to make electrical performance calculation that ends with obtaining of an optimized radome structure with a changing honeycomb layer thickness on basis of three dimensional surfaces. The male mold used to manufacture radome often has tolerances that lead to inaccuracy of the electrical thickness for the radome wall structure. This paper, by using reverse iteration algorithm, obtains accurate outer contour by using point coordinates and its normal vector of the finished male mold, angle positions of points and thickness formulation of radome. As reverse iteration goes on, point coordinates on outer surface of radome as well as the transformation matrix that changes inner real normal vector to normal vector of outer surface converges. When accuracies are achieved, reverse iteration ends. Using obtained outer surface coordinates, its normal vector as well as the thickness formulation, the outer surface of the two layers of honeycomb can be formed. With this method, precise electrical performances can be achieved even when the shaping mold has discrepancies and tolerancies.

EFFECT OF INTERFACIAL FRICTION ON IMPACT ENERGY ABSORPTION CAPACITY OF KEVLAR FABRIC

SHI Chun-xu, DUAN Yi-ping, REN Jia-jun

2015, 0(9): 57-63.

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A large number of experiments have proved that projectile-yarn and yarn-yarn friction have a significant effect on fabric's ability to absorb impact energy. It has been shown that projectile-yarn and yarn-yarn friction is an important factor in affecting the energy absorption properties of fabric in the spherical projectile impact on fabric. However, how the friction plays a role is not well known during flat projectile impact. In this paper, a multi-scale three-dimensional finite element model of fabric is established and combined with LS-DYNA to simulate the flat projectile impact on fabric with four edges clamped. Modeling indicated that yarn kinetic energy and yarn strain energy is the main energy absorption mechanism but sliding dissipated energy is not, however smaller friction help promote mutual movement between yarns,and increase the interaction time between projectile and fabric, which help to improve fabric's ability of energy absorption indirectly. Yarn-yarn friction plays a main role on fabric's ability of energy absorption, while projectile-yarn friction just has weak effect.

EXPERIMENT RESEARCH ON DEICING AND SNOW-MELTING OF SELF-HEATING AIRFORCE PAVEMENT WITH CONTINUOUS CARBON FIBER HEATING WIRE

EXPERIMENT RESEARCH ON DEICING AND SNOW-MELTING OF SELF-HEATING AIRFORCE PAVEMENT WITH CONTINUOUS CARBON FIBER HEATING WIRE LI Chun-ming, XU Wei, LI Guang-yuan, ZHOU Hai-zhong

2015, 0(9): 64-69.

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In order to study the deicing and snow-melting rules of 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. Experiments in different input power and thickness were implemented, and the mechanism was analyzed. The results indicates that setting a insulation layer in concrete slabs could reduce thermal storage and improve the efficiency of snowmelt deicing. Time-consuming and power consumption were mainly decided by the input power and thickness of snow and ice. Within a certain rang, every 50W/m² power increase, the time of snow-melting would short for 1.14h, and 0.25kW·h/m²of electricity would be saved; each 1cm snow thickness increase, the time of snow-melting would prolong 0.69h and the power consumption would increase 0.35 kW·h/m². In addition, pavement preheating can not only avoid snow cover and ice up, energy could be save by using intermittent power supply.

INFLUENCE OF GLASS FIBER ON ACID RESISTANCE OF GLASS FIBER REINFORCED COMPOSITE MATERIALS

ZHOU Qiao, HOU Rui-gang

2015, 0(9): 70-73.

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Glass Fiber Reinforced plastics (FRP) is effectively used in the coal-fired power plant chimney for corrosion resistant material recently. The mass loss ratio of the fibers and its composites after treatment were investigated. The surface morphologies were characterized using scanning electron microscopy. The result shows that the type of glass fiber influences the acid resistance of FRP obviously. ECR promoted the acid resistance of FRP.

LOW-VELOCITY IMPACT PERFORMANCE OF OUT OF AUTOCLAVE PREPREG SYSTEM T700SC/#2510

KONG De-shuan, GUAN Guo-yang

2015, 0(9): 74-76.

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The document tested the low-velocity impact performances (damage resistance and damage tolerance) of an Out of Autoclave (OOA) prepreg composite systems T700SC/#2510. The relationship curves between dent depth and impact energy per thickness millimeter (d-e), damage area and impact energy per thickness millimeter (S-e), compression strength after impact and notch depth (σ-d) are obtained with three kinds of classic layup. And the compression strength after impact with 6.7J/mm energy of three batches of this OOA prepreg quasi-isotropic laminates is also obtained. The results show that, the damage on the impact surface of the composite systems T700SC/#2510 is barely visible, but the internal damage area is very big. There is an inflexion in all the relationship curves of d-e, S-e and σ-d. The quasi-isotropic layup can absorb more impact energy, but results in a larger delaminating damage area. The CAI strength of this OOA prepreg quasi-isotropic has approached the target of the second generation OOA prepreg.

STUDY ON A NOVEL PHENOLIC RESIN AND ITS COMPOSITES FOR PULTRUSION PROCESS

TIAN Mou-feng, TAN Juan-juan, WANG Lei,SUN Yi

2015, 0(9): 77-82.

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A novel non-acid phenolic resin named F-613 for pultrusion process was studied. The structure, molecular weight, viscosity, curing properties and gelling time of this resin were characterized by FTIR, GPC, rheometer, DSC and etc. The DSC curve of F-613 phenolic resin displayed a single exothermic peak existing lower temperature area contrast to 9450 phenolic resin with two exothermic peaks in higher temperature area. Moreover, F-613 phenolic resin retains shorter gel-time at high temperature. The analysis results indicated that F-613, with shorter gel-time and lower exothermic peak temperature, is more applicable to pultrusion process because of its low viscosity, high activity and rapid solidification. Compared with that of 9450 phenolic resin, the formula and pultrusion process of F-613 were simpler under the condition of the same properties. The mechanical properties of glass fibre-reinforced composites shows no significant differences. But, the distinct properties of F-613 phenolic resin systems is no corrosion to mould during the pultrusion process.

INVESTIGATION ON WEAR PROPERTY OF ABRASION-RESISTANT COMPOSITES MANUFACTURED BY INTEGRATIVE MOULDING

ZHANG Lian-wang, LI Bao-wei, ZHONG Xiang-yu, BAO Jian-wen

2015, 0(9): 83-86.

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This article made a try on the prepration of abrasion-resistant composites by integrative RTM moulding. Wear testing of said composites was performed. Surface profiles of samples after wearing test were drawn by Phase Shift MicroXAM-3D. Granularity ansysis of hardness particle which was the main component of abrasion-resistant coating was conducted by laser granularity analyst. The inside microstructure of abrasion-resistant composites was observed by scanning electron microscope. The results demonstrated that the friction coefficient was coherent with ultimate indent depth, namely, the less the friction coefficient was, the less indent depth was. The use of abrasion-resistant composites in high speed conditions could be limited because resin was the matrix of abrasion-resistant coating.

EFFECT OF WAVINESS DEFECT ON COMPRESSIVE BEHAVIOR OF COMPOSITE LAMINATES

WU Wei-qing, ZHU Jun, WANG Ji-hui, ZU Lei

2015, 0(9): 87-92.

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We adopted VARI process and the autoclave molding process to manufacture compression samples with different reinforced fibers and compression samples with fiber waviness defect. The results of the compression tests showed that Young's modulus and compressive strength degraded seriously with the increase of fiber waviness ratio, and fiber waviness had greater influence on compressive strength. Meanwhile, uniform waviness had a greater effect on compressive strength and Young's modulus than graded waviness. Interlaminar shear stress was found to be the dominant failure mechanism. Moreover,the samples are prone to have transverse shear failure on the position of maximum misalignment angle.

PROGRESS OF RESEARCH ON THE HEAT RESISTANCE OF POLYTRIAZOLE RESIN

SHEN Zhen, ZENG Jin-fang, WANG Xiu-yun

2015, 0(9): 93-98.

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In this paper, the methods of improving the heat resistance of polytriazole resin were generalized. The present situations of the effects of chemical structural frame, curing condition and nano materials on the heat resistance and mechanical properties of polytriazole resin were emphatically introduced. Finally, some problems on the present study and the development prospect of the improvement of heat resistance of polytriazole resin were also investigated.

BOND BEHAVIOR OF FRP REBAR AND CONCRETE

ZHANG Wei-dong, WANG Zhen-bo, SUN Wen-bin

2015, 0(9): 99-103.

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Based on the results about bond behavior of FRP rebar and concrete under unfavorable conditions around the world,test methods of bond behavior are comparatively analyzed, the research advancement and present status of bond slip behavior of FRP rebar and concrete under unfavorable conditions (including high temperature, freezing and thawing cycling, chlorine salt, alkaline solution, dry and wet cycling) are introduced. Through comparative analysis of the present achievement, some shortcomings are pointed out and several suggestions are forwarded.

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