COMPOSITES SCIENCE AND ENGINEERING

EXPERIMENT AND DESIGN METHOD OF THE COMPOSITE REINFORCED CFRP-PCPS PRISM EMBEDDED IN SHEAR STRENGTHENED BEAMS

DENG Yu, GAN De-li, YANG Yong, YANG Xi-tao

2016, 0(12): 5-10.

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In this paper, the shear test of 9 reinforced concrete beams strengthened with CFRP-PCPs composite bars is carried out. The effects of different parameters on the shear strengthening of concrete beams are considered, including different embedding distance, different embedding angles, different tension control stress and embedded composite bars made of different materials. And, the destruction form of reinforced concrete beams strengthened with embedded CFRP-PCPs composite bars is analyzed. According to the experiment, the calculation formula of shear strength is obtained. Comparison results show that the calculated values agree well with the experimental results. The experimental results indicate that the composite reinforced CFRP-PCPs prism has significant effects on the shear behavior of concrete beams.

STUDY ON MECHANICAL PROPERTIES OF HYBRID ULTRA-FINE STEEL-POLYPROPYLENE FIBER REINFORCED CONCRETE

WANG Chen-fei, JIAO Jun-ting

2016, 0(12): 11-14.

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In order to study the mechanical properties of hybrid fiber reinforced concrete, 9 different groups of concrete specimens with ultra-fine steel fiber (UFSF) and polypropylene fiber (PPF) were tested according to the compressive strength and splitting tensile strength test, and the influence of the volume fraction of UFSF and PPF were analyzed. The results indicate that compressive strength, splitting tensile strength and tension-compression ratio were increased after adding a reasonable volume of hybrid fiber. Hybrid fiber concrete has noticeable ductile characteristics. The volume fraction of UFSF was proved to have the biggest influence on the mechanical properties of concrete. The mechanical properties of the hybrid fiber reinforced concrete were enhanced effectively with the increase of UFSF. The mechanical properties of concrete were not enhanced linearly with the volume fraction of PPF. Hybrid fiber concrete with 0.1% dosage of PPF and 1.5% dosage of UFSF achieved the best mechanical properties. Besides, the compressive and strength was increased by 19.42%, splitting strength was increased by 56.78%, and tension-compression ratio was increased by 30.16%.

THEORETICAL STUDY OF MODE I INTERFACIAL DELAMINATION OF SANDWICH STRUCTURE WITH GFRP SKINS AND A FOAM CORE UNDER COUPLING EFFECTS OF TEMPERATURE AND LOADS

ZHANG Chen-hao, WANG Lu, CHEN Hao

2016, 0(12): 15-22.

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Composite sandwich structures are widely used in many fields due to their high strength to weight ratios, high stiffness to weight ratios, anti-corrosion ability and other characteristics. However, the structures are faced with a variety of injuries under active conditions. Actually, in the existing applications, the open type delamination (mode I interfacial delamination) between the surface layer and the core material is a common failure mode under the coupling effects of temperature and loads. Based on conservation of energy and elastic foundation beam theory, expression of strain energy release rate is analyzed, while the crack between the surface layer and the core material is expending. At the same time, according to the contrastive analysis between the calculated values and experimental values of sandwich double cantilever beam (DCB), the correctness of the expression of strain energy release rate under the coupling effects of temperature and loads can be verified.

INVESTIGATION ON THE ACOUSTIC EMISSION CHARACTERISTICS DURING THE DAMAGE OF GLASS FIBER COMPOSITE

MENG Chao, PENG Wei-dong, NING Xiao-bo, TANG Qing-ru

2016, 0(12): 23-27.

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Glass fiber composite materials are widely used in aerospace, automobile manufacturing and other fields because of its superior performance in structure. A set of acoustic emission detection system consist of TMS320F28335, storage and display were designed based on the damage properties of glass fiber composite materials and the characteristics of AE signals. The waveform and frequency characteristics of acoustic emission signal are analyzed by the time frequency analysis method of modern wavelet transform, and three main frequency bands and corresponding three basic damage modes of the glass fiber composite acoustic emission signal frequency are determined.

ON-LINE MONITORING OF COMPOSITE T-STIFFENED PANELS SUBJECTED TO LOW-VELOCITY IMPACT BASED ON THE FBG SENSOR TECHNOLOGY

ZHOU Yu-jing, FAN Guang-hong, REN Ming-wei, CHEN Guo-song

2016, 0(12): 28-33.

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The FBG sensors, embedded in the triangle area of the T-stiffened panels, were employed to online-monitor the strain of the composite T-stiffened panels during its impact testing and compression testing. The effect of impact location and impact energy on the strain measured by the FBG sensors was studied. The accuracy of the FBG sensor during the impact and the compression was analyzed. The experimental results showed that the max-strain of impact measured by the FBG sensors decreased with the increase of the distance between the location of impact and the FBG sensors (impact distance) under the same impact energy. The FBG sensors did not fail while visible damages are induced in composite T-stiffened panels, and the spectrum of the FBG sensor maintained single peak, the accuracy of the FBG sensor was assured. The procession of the impact and the compression monitored by FBG sensors on-line were initially realized.

LARGE SECTIONAL TYPE WIND TURBINE BLADE FINITE ELEMENT MODELING AND STIFFNESS AND MODAL ANALYSIS

QIN Chao, HOU Bin-bin, CHEN Kang, LIU Qi-xing

2016, 0(12): 34-37.

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In this paper, the finite element model of a 54 m segmented wind turbine is established, and the stiffness and modal analysis are carried out for the segmented blades. Calculation results show that, under the four limit condition, the segmented blades stiffness and the original blade are basically the same: Segment is consistent with the original leaf blade in the first two modes and the natural frequencies are basically consistent. Blade segments of blade vibration performance have a great impact, verifying the rationality of the segmented blades structure stiffness and the vibration performance.

STUDY ON REACTION KINETICS OF MODIFIED CYANATE ESTER

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

2016, 0(12): 38-42.

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The cure kinetics of phenol modifying cyanate ester resin system were investigated by non-isothemal DSC. The results show the organic titanium catalyst could reduce the active energy of resin. Thus, the reaction temperature could be reduced and cure reaction rate could be accelerated remarkably. The cure of modified cyanate ester resin was almost a first-order reaction. The organic titanium catalyst could not change the reaction mechanism of these resin system.

STRUCTURE AND PROPERTIES OF VACUUM ASSISTED MOLDING COMPOSITE FOR DRY FIBER

DUAN Zhen-jin, PAN Li-jian, LIU Wei-ping, WANG Zhao-zhao

2016, 0(12): 43-48.

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By simulating principle of dry fiber placement, laying the continuous thermal plastic fiber as a setting material in carbon fiber fabrics of non crimp, preparing fabric preform with hot-pressing conditions, and fabric preform was prepared by vacuum assisted resin infusion (VARI). The sample was prepared by using different preset pressure, predetermined temperature and the content of thermoplastic fiber. The volume content, mechanical properties and microstructure of the composites were determined. Results show that with the increase of preset pressure, the fiber volumes contents decrease at the same pressure of tackificatio. It satisfied with the compression constitutive model of fabric. Fiber volume contents tend to be constant when the pressure of tackifier is up to 1 MPa, the fiber volume content tended to be stable, up to a maximum of about 65%. Under the same predetermined pressure, as the shaping material dosage increased, fiber volume content was decreased, as well as the mechanical properties. The influence of the scheduled temperature on the performance of composite is mainly determined by whether the shaping material itself is melting or not. The occurrence of melting sizing materials will have an adverse effect on composite material properties.

STIDY ON THE VISUALIZATION SYSTEM OF FIBER PLACEMENT BASED ON OPENGL

LI Shuan, XU Dong-liang, ZHOU Xu-dong, HU Bin

2016, 0(12): 49-54.

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Automatic fiber placement CAD/CAM software is the key technology to realize the automatic composite materials manufacturing. According to the characteristic of equipment and the process of auto fiber placement, visualization system of fiber placement is developed using the OpenGL in VC6.0 platform. The system can be used to realize the core mold import and reconstruction, the establishment of the topological relationship between vertices, lines, and trianglesis in the system, which can provide data support for the follow-up visual display. Through the study of the kinematics analysis of the laying process to determine the trajectory of point coordinates, the fiber was then drawn. The surface of the core is laid with using the fixed angle algorithm through the visualization system, which can verify the validity and effectiveness of the visual system.

EXPERIMENTAL STUDY ON THE COMPRESSIVE PERFORMANCE OF AERO SHORT-BEAM COMPOSITE STIFFENED PANEL

YIN Xiang, FENG Yu, ZHANG Hui, ZHOU Xiao-guang

2016, 0(12): 55-59.

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Compressive experiment on the aero short-beam composite stiffened panel was carried out in this paper. The fracture of stiffeners and splitting of panels as well as the failure of either ends are involved in the failure modes. However, the debonding of stiffeners to panels does not appear. At the beginning of loading history, the load-strain curve exhibits linear increasing trend while the out-of-plane displacements are around 0 mm. When the compressive loads exceed the critical buckling load, the strain-load curve tends to branch off. At the same time, there is a drastic rise in the displacement-load curve. The results indicate that short-beam composite also exhibits the post-buckling carrying capacity, which is relatively small. The failure occurs very soon in the short-beam composite stiffened panels if the buckling phenomenon occurs. The results obtained by FE software is consistent with the experimental results. The finite element results indicate that the buckling modes of specimens is the local buckling of panel between stiffeners.

FRACTURE PARAMETERS DETERMINATION AND APPLICATION OF ADHESIVE BASED ON COHESIVE ZONE MODEL UNDER THE CONDITION OF MIXED MODE Ⅰ/Ⅱ

WANG Yue, ZHAO Xia, MU Zhi-tao, HAO Jian-bin

2016, 0(12): 60-64.

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A three dimensional and elastic finite element model for adhesive bonded single lap joint of aluminum alloy by using cohesive zone model was established, which was proved to be valid by comparing with the shear stress and peel stress distribution of the adhesive layer in G-R analysis model. By simulating the tension test and fitting the load-displacement curves, the fracture parameters of adhesive cohesive zone model were obtained, which were then applied to predict the residual strength of adhesively bonding composite repaired structures with double-edge cracks. The results show that the relative error between the prediction and the experiment is 3.8%, which proves the validity and high accuracy of the method. It′s helpful for carrying capacity′s analysis of adhesively bonding composite repaired structures.

STUDY ON TRIBOLOGICAL PROPERTIES OF RESIN-BASED FRICTION MATERIALS REINFORCED BY HYBRID FIBERS

ZHANG Chao, ZHAO Liang-ji, ZHANG Qi-shun, GAO Xin-yu

2016, 0(12): 65-69.

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The phenolic resin modified by nitrile rubber as matrix, Kevlar/glass/steel/copper fibers as the hybris fibers, prepared friction materials and tested the tribological properties of the materials under dry friction conditions by the friction and wear testing machine, used the scanning electron microscopy (SEM) to observe the surface of friction materials, studied the effect of different hybrid fiber components on friction material properties. The results show that the friction coefficient and wear rate decrease with the increase of sliding speed, and which have no obvious change trend with the increase of load. In the friction process, the wear form of the friction material which containing four fibers is furrow and the plastic deformation; the wear form of the material not containing Kevlar/glass hybrid fiber is mainly fatigue wear; the wear form of the material not containing steel/copper hybrid fiber is mainly adhesive wear. Thus, adding hybrid fiber can effectively improve the friction coefficient of material, reduce the wear rate, and obviously improve the tribological properties of the material.

MECHANICAL RESPONSE ANALYSIS OF GLASS FIBER REINFORCED PLASTIC MORTAR PIPE UNDER DYNAMIC LOAD

CHEN Zhao-nan, WEI Lian-yu, ZHENG Yan-jun, SHI Hua-wang

2016, 0(12): 70-74.

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In order to analyze the mechanical response of the buried FRPM pipe under different dynamic loads, we selected a 22 t vibration roller and 39.4 t and 60.4 t heavy engineering trucks to test the vibration velocity time curves of shallow buried FRPM pipe during construction, and applied the FFT method to determine vibration frequency and amplitude of the FRPM pipe. The results show that when 22 t vibration roller is strong earthquake, the maximum vibration velocity and amplitude are greater than the vibration response value of the heavy engineering trucks, which agrees with the actual roller with the large pressure. But the three dynamic loads have low influence on culvert mechanics response of buried pipe. The result explains the high stiffness of the pipe, and provides theoretical basis for the construction and application of the FRPM pipe.

COMPARABLE ANALYSIS OF ANCHORING METHODS OF FRP SHEETS

FU Ting-ting, FENG Shao-yun, FAN Wen-zhong

2016, 0(12): 75-80.

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FRP (Fiber Reinforced Polymer) strengthening methods have been widely applied to bridge structures. Although the methods using FRP sheets can improve the flexural load-bearing capacity of strengthened structures,they often suffer from the premature debonding failure. The failure can be effectively circumvented by anchoring systems, which can improve utilization of the strength of FRP sheets. This paper reviews the existing anchoring methods of FRP sheets and analyzes their strengthening effects.

STUDY ON ELECTROCHEMICAL SURFACE MODIFICATION OF PAN-BASED CARBON FIBER OF HIGH STRENGTH AND MIDDLE MODULUS

XU Xian-liang, ZHANG Yue-yi, MA Quan-sheng, CONG Zong-jie

2016, 0(12): 81-85.

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In this paper, the carbon fiber of high strength and middle modulus was studied. Mechanical properties and surface activity characteristics of high strength and middle modulus, and its effect on the interlaminar stear strength (ILSS) of composites material were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and dynamic contact angle instrument. It is found that current density has remarkable effects on fiber surface element content, -OH, -C=O and -COOH functional group content and polar free energy. When current density increases to 0.23 mA/cm², the polar free energy of carbon fiber reaches the maximum value of 5.5 m/Nm, and the ILSS reaches 111 MPa, which increase by 10 times and 68.2%, respectively, as compared to untreated fibers.

THE STRUCTURE STRENGTH ANALYSIS OF GLASS FIBER REINFORCED PLASTIC SLIDE

CHEN Peng, CHEN Hou-wang, LING Wei-ya, XU Jian-ping

2016, 0(12): 86-89.

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The glass fiber reinforced plastic slide is a kind of aquatic amusement facilities which belongs to the national special equipment, and the structure safety directly relates to the visitors safe. Considering the anisotropy of glass fiber reinforced plastic, the fluctuating load caused by visitors sliding on the slide, and the limit environmental load, the slide structure was analyzed by the ANSYS and checked by the GB 8408—2008. The study provides theoretical basis and reference to the optimization design of aquatic amusement facilities and improves the safety of the structure.

IMPACT SIMULATION ANALYSIS FOR FREE FALLING STATUS OF COMPOSITE TORPEDO SHELL

ZONG fang-yong, CHAI Peng-jun

2016, 0(12): 90-98.

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The drop processes of composite torpedo shell including free falling status, contacting with ground status, impacting on ground status and stressing status were simulated by the nonlinear material module of mechanical motion in ALGOR. The effect of ground and drop-posture on the composite torpedo shell during the dropping was investigated by simulating the four statuses respectively. Based on the comparison and analysis of simulation results, including force, stress, strain and displacement, the dropping resistance properties of torpedo composite shell were obtained, which was used to evaluate the impact performance of composite torpedo shell.

LIGHTWEIGHT RESEARCH OF CARBON FIBER/EPOXY BATTERY BOX

WANG Jia-nong, ZHAO Xiao-yu

2016, 0(12): 99-102.

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According to the advantages of lightweight, high specific rigidity and strength of the composite material, it has been designed for the light weight of a certain type of electric vehicle battery box structure, which aims at reducing the weight of the electric vehicle. By applying Patran&Nastran as the analysis platform, this study uses the finite element analysis method to compare the bearing capacity of the battery box structures of two kinds of steel and carbon fiber/epoxy composite. Then, a reasonable structure of carbon fiber/epoxy battery box was designed. On the basis of Tsai-wu strength theory, the strength of carbon fiber/epoxy battery box was checked. Results show that the bearing performance of the battery box is not reduced under the condition of reducing the 64% weight of the battery box.

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