COMPOSITES SCIENCE AND ENGINEERING

MECHANICAL PROPERTIES ANALYSIS OF FRP SANDWICH PLATE FRAME STRUCTURE WITH A LARGE OPENING

KONG Ling-bin, ZHANG Huo-ming, FANG Gui-sheng, TIAN Zhong-ren

2017, 0(6): 5-11.

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FRP composite material is a new type of industrial materials, which is widely used in many fields, including the shipbuilding industry. In the design of FRP hull, we must make a simulation of related structure′s strength and stiffness in advance for avoiding ship hull damage caused by external forces such as collision. In this paper, the FRP Yachts sandwich plate frame structure with large openings were selected as the object of our research, and the finite element method was used to analyze the mechanical properties of the target structure. Based on the calculation results, the displacement and stress distribution of the target examples were checked. In this way, the effects of various operating conditions on mechanical properties of the target structure were obtained, and some meaningful conclusions were proposed at the end of this article.

STUDY ON THE AGING MECHANISM AND FLEXURAL BEHAVIOR OF GFRP REINFORCED CONCRETE MEMBERS UNDER LONG-TERM CORROSION ENVIRONMENT

LI Xing, SUN Li-xiang, LIN Peng-zhen, YANG Zi-jiang

2017, 0(6): 12-17.

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In order to study the aging mechanism and flexural behavior of GFRP reinforced concrete members under long-term corrosion environment, the effects of moisture, temperature and alkali environment on the tensile strength, effective tensile area and bond strength of GFRP bar were analyzed separately. Based on the change of the relationship between the material aging and cooperative work with concrete, the calculating formula of the flexural capacity of the normal section of the aging GFRP bar is derived by constructing the new geometrical condition, and using the derived formula to analyze the influence of aging rate on the bearing capacity of the component. The researches show that GFRP reinforced concrete member under the long-term effect of the corrosion environment, GFRP tendons aging, its tensile strength, effective tensile area and bond properties have different degrees of reduction. As the aging rate of GFRP reinforced materials increases, the loss rate of flexural capacity of the component is also increasing. When the aging rate is 27%, the flexural capacity of the component is also lost by 25.97%.

IMPACT DAMAGE OF HYGROTHERMAL CONDITIONED CARBON EPOXY COMPOSITE LAMINATES

GU Wei-min, LIU Qi-wen, LIU Li-sheng, ZHAGN Jiang-tao

2017, 0(6): 18-22.

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High velocity impact damage of carbon fiber-reinforced polymer laminates under hygrothermal environment is investigated. Composite laminate specimens were dried in a vacuum oven, and a part of specimens were immersed in water at 70 ℃ for 37.7 days. Then all specimens were impacted by conical projectile with the velocity of 45m/s, 68 m/s, and 86 m/s. The laser velocity measurement device was used to measure the striking and residual velocity. The impact damages of composite specimens under different environments were tested by using ultrasonic C-scan, digital microscope system, scanning electron microscope (SEM) and visual inspection. The experiment results show that, damage projection area increases with the increasing striking velocity. At the case of low velocity, the hygrothermal environment has a greater impact on the damage projection area of carbon fiber-reinforced polymer laminates. The interlaminar properties of carbon fiber-reinforced polymer laminates under hygrothermal environment reduced, while the energy absorption ability increased.

NUMERICAL SIMULATION ON THE TEMPERATURE CHANGE OF LARGE CAPACITY HOOP-WRAPPED COMPOSITE CYLINDERS FOR TUBE TRAILERS DURING REFUELING AND NATURAL COOLING

LIU Feng-xuan, DENG Gui-de, LIANG Hai-feng, JI Fang

2017, 0(6): 23-27.

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A numerical model was established for the predication of the temperature rise of Large Capacity Fully-wrapped Composite Cylinder on Compressed Natural Gas Vehicles (CNGV) during its refueling and cooling. A CNG tank is regarded as an object of study, in which working cubage is 2500 L and working pressure is 20 MPa. Computational fluid dynamics (CFD) software Fluent 17.1 was applied to simulate the refueling process of 1800 s and the static cooling process of 5400 s. The setting process of the Finite Element Method of this simulation was described in detail. The flowing direction of gas, temperature distribution in the cylinder and the temperature patterns of the wall during its filling and cooling were emphatically analyzed. The simulation results show that high temperature is concentrated on the tail of the vessel, and the temperature of the wall is below the allowable temperature during all procedure in this simulation.

STACKING SEQUENCE OPTIMIZATION OF COMPOSITE LAMINATE BASED ON IMPROVED DUAL POPULATION GENETIC ALGORITHM

ZHENG Guo-wen , XIE Xi-hua

2017, 0(6): 28-32.

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In order to solve the problem of premature convergence or slow convergence of algorithms, which can be easily seen in the progress of composite laminates design and optimization, through combining multi population genetic algorithm and adaptive genetic algorithm, a new improved dual population genetic algorithm with a adaptive operator is proposed. Taking as an example of symmetric laminated for test, a Patran finite element initial model is established. And, with Matlab, the main program of genetic algorithm and data transfer procedures is compiled, by which the Nastran input and output files can be written and read. Then a fitness function based on Tsai-Wu failure criterion is established, and the laminate stacking sequence is optimized. Compared with the traditional genetic algorithm, the results show that the improved algorithm can improve the optimization efficiency obviously, and can effectively converge to the global optimal solution, consequently providing a new solution to the optimization problem of composite structures.

THE INFLUENCE OF VOID CONTENTS ON TRANSVERSE MECHANICAL PROPERTIES OF UNIDIRECTIONAL COMPOSITES

LI Bo, WAN Xiao-peng, ZHAO Mei-ying

2017, 0(6): 33-38.

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Considering the random distribution of fibers and voids, the representative volume element (RVE) of the composites microstructure with random voids is generated by random algorithm. Then, by creating finite element model of RVEs and considering the elasticity-plasticity of matrix and bilinear traction-separation law for interface, the effect of void contents on transverse behavior of unidirectional composites is simulated by the finite element analysis. It is found that the effect of random distribution of voids is small on transverse properties. When void content is less than critical value, the influence of voids on transverse properties is weak relatively. When void content is more than critical value, the reduction in transverse modulus, transverse tension strength and transverse compression strength becomes signiticant.

EXPERIMENTAL AND THEORETICAL ANALYSIS ON FLEXURAL BEHAVIOR OF STEEL PLATE-GFRP COMPOSITE BRIDGE DECK

HUA Peng, FANG Hai, LIU Wei-qing, XU Xin

2017, 0(6): 39-45.

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Based on the glass fiber reinforced polymer (GFRP),which has the advantages of light weight, high strength, corrosion resistance, a new type of composite bridge deck was puts forward. GFRP plates were sticked on the surface of steel deck plate and they were took as orthotropic steel bridge deck waterproofing and anti-corrosion layer, which plays a critical role of enhancing the stiffness of steel plate. On the completion of a test for the material performance of composite bridge deck, the four-point bending test for the composite bridge deck under the positive and negative bending moment was implemented. The load-deformation curve and load-strain curve of the specimens were obtained from the test. The stiffness, the mid-span deformation and stress calculation formulation of steel plate-GFRP composite bridge deck were deduced according to conversion section theory. In addition, making a comparison between theoretical values and the experimental values, deformation and stress analysis of orthotropic steel plate by using finite element software under four pavement models, it is concluded that GFRP plate sticked on the surface of steel plate can effectively improve bearing capacity and stiffness of steel plates, reduce steel surface stress and the risk of cracking. Theoretical value of steel plate-GFRP composite bridge deck bending performance is consistent with the experimental value well.

STUDY ON DIFFERENT TECHNOLOGY PROCESS OF DRILLING CARBON FIBER REINFORCED PLASTICS

WANG Gong-dong, PENG Tian, LI Ying-chi, ZHOU Li

2017, 0(6): 46-50.

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Drilling induced delamination often caused the peeling at the entrance and the pushing at the exit of composite materials. Because of the thrust force being the main factor of delamination, it was necessary to control the thrust force for improving hole quality. This paper designs three different drill process consist of twist drill (without pilot hole), twist drill (with pilot hole) and step drill. Based on the existing axial thrust force model of these processes, the thrust force at the beginning of delamination with diameter ratio, the thrust force with hole depth and feed rate were analyzed, and the hole quality was observed by SEM. The results indicate that step drill and pilot hole can drastically decrease the thrust force and improve the hole quality.

EFFECT OF CARBON NANO-FIBER ON GLASS FIBER/EPOXY COMPOSITE

LV Guang-chao, LU Zhi-li, DONG Meng-yao, LIU Chun-tai

2017, 0(6): 51-56.

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In this paper, vacuum assisted spray method was used to fabricate the Advantex glass fiber/epoxy composite with 0.5% CNF. The Advantex galss fiber/epoxy composite saturated permeability was measured by the unidirectional saturated flow method, and the mechanical properties at different temperatures and solid particle erosion resistance were measured and investigated. The results indicate that after adding 0.5% CNF, the parallel direction of the Advantex glass fiber saturated permeability decreased by 2~6 times, and the perpendicular direction of the fiber saturated permeability decreased by 2~5 times. When the porosity is less than 0.44, the saturated permeability of two direction had little difference, which are close to zero. The influence of 0.5% CNF on pure epoxy and perpendicular direction composite mechanical properties and solid particle resistance properties are much smaller than those of the parallel direction composite. At high temperature, the addition of the 0.5% CNF improves the stability of the tensile strength of perpendicular Advantex glass fiber/epoxy composite.

RELATIONSHIP BETWEEN LOW IMPACT ENERGY AND THE DEPTH OF GLASS FIBER REINFORCED EPOXY COMPOSITES LAMINATED PLATES

DING Ming-cong, LI Di-hong, HOU Yun-fen, WANG Jia-jun

2017, 0(6): 57-63.

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In this paper, two types of glass fiber reinforced epoxy composites laminated board with unidirectional plate and multidirectional plate are used. The impact test was performed using free fall impact testing machine. Digital microscope was used to describe the damage morphology. By introducing factor K and establishing a quantitative relationship between the different impact energies and the pit depth, the relationship and the impact damage morphology characteristics under different impact energy are compared. According to the relationship between the depth of the pit and the factor K, the energy value of the impact is measured by measuring the pit depth. According to the impact energy value, the damage of the structure can be judged by experience.

RESEARCH ON PROCESSING APPLICABILITY OF IN-MOULD POLYURETHANE GEL-COATINGS USED FOR WIND TURBINE BLADES

MU Shu-xiang, ZHOU Lian-xia

2017, 0(6): 64-67.

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Using in-mold coatings is an effective way to improve the coating efficiency of wind turbine blades. There are some special requirements for the processing performance of the in-mould coating system compared with the outer-mould coating system for wind turbine blades. This paper studies the processing applicability of three kinds of in-mold polyurethane gel-coatings used in wind turbine blades. Through research on manipulability, in-mold time, pull-off strength between gel-coating and glass fiber reinforced epoxy composite, release properties in actual wind blade mold, and the observability of the defects in glass fiber reinforced composite covered by coating, it draws a conclusion that two kinds of in-mold polyurethane gel-coating are fit for the production process of wind turbine blades.

BOND BEHAVIOR BETWEEN BFRP BARS AND BASALT FIBER REINFORCED RECYCLED AGGREGATE CONCRETE

YIN Tian-tian, LIU Hua-xin, KONG Xiang-qing, WANG Xue-zhi

2017, 0(6): 68-74.

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To study the bond properties between BFRP bars and basalt fiber recycled concrete, the center pull-out test with 42 specimens was performed. The influence of the replacement ratio of recycled coarse aggregate, the diameter and the surface characteristics of the BFRP bars were studied. The results indicate that with the increase of the replacement ratio of recycled aggregate, the bond stress of peak value decreases gradually, and the peak slip decreases firstly and then increases. With the increase of the diameter of BFRP, the bond stress increases gradually, and the peak value of bond stress is gradually increased, the peak slip value corresponding to the peak bond stress is gradually increased. But the overall change range is very small. The surface condition of the BFRP bar has greatly influence on the bond behavior of the basalt fiber recycled concrete and the BFRP bar. Using the improved BPE model, CMR model, and the continuous curve model of the calculated value and the experimental value of the comparative analysis of the ultimate bond stress, the bond-slip constitutive relation model is obtained by nonlinear regression analysis, and the calculated values of the model are in good agreement with the experimental results.

IMPROVED PROPERTIES FOR POLYPHENYLENE OXIDE/NYLON 6 ALLOY REINFORCED BY ARAMID FIBER

WANG Hong-hua, MEI Qi-lin, XIA Xue, WANG Cong

2017, 0(6): 75-79.

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Polyphenylene oxide (PPO) is a high strength engineering plastic with high melt viscosity, while aramid fibers (AF) is a high-tech fibers with good mechanical performance and smooth surface. Thus, the impregnation effect of AF in PPO matrix is very poor. In order to prepare PPO reinforced by AF composite materials, the surface of the AF can be modifided through the plasma by adding oxygenous groups on the one hand, preparing PPO/nylon 6(PA6) blend to reduce the melting viscosity on the other hand. In this article, polyphenylene oxide/nylon 6 (PPO/PA6) alloy modified by styrene-butadiene copolymer grafted by maleic anhydride (SEBS-MAH) were studied, and the PA6/PPO/SEBS-MAH composite materials reinforced by aramid fiber were prepared. Experimental results show that PA6 can improve the processing property of PPO/PA6 system and reduce the melting viscosity. SEBS-MAH can improve the compatibility of PPO/PA6 blend system, mechanical properties and the glass transition temperature of blend. Aramid fiber (AF) can improve the PA6/PPO/SEBS-MAH mechanical properties and friction properties of blending system. And, the rigidity of the blend system was improved as shown by the Tanδ-temperature curves.

CHARACTERISTICS OF THERMAL AGING ON BENDING PROPERTIES OF 3-D INTERLOCK COMPOSITE MATERIAL

WANG Ming-ling, CAO Miao, GU Bo-hong, SUN Bao-zhong

2017, 0(6): 80-84.

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In this paper, the bending properties of 3-D carbon/epoxy interlock composite unaged and aged for 16-days at different temperature (90 ℃, 110 ℃, 180 ℃) were studied by quasi-static loading. The influences of aging temperature on bending properties were observed by macroscopic observation and SEM as well. The influences of aging temperature on epoxy properties, post-curing, heat flow and chemical structure were studied by differential scanning calorimetry (DSC) and infrared spectrum (IR Spectrum), respectively. The result indicated as follows. The post-curing and thermal degradation can be found in epoxy aging at the same time. For Composite aged for 16 days, the bending strength of composite aged at 90 ℃ increased obviously because the post-curing of epoxy play an important role in aging. When composite aged at 110 ℃, the bending strength decreased unobviously which were caused by slightly thermal degradation. For composite aged at 180 ℃, the bending strength declined distinctly and the flexural modulus decreased as well due to the strong thermal degradation of the epoxy resin and the fiber/resin interface crack which were observed by SEM. In addition, less damage area on top of composite aged at 90 ℃ than others could be found form the damage photographs. These were consistent with the strength characteristics which indicated in above situation that composite aged at 90 ℃ had better bending properties.

STUDY ON INJECTING REPAIR TECHNOLOGY OF DELAMINATION FLAW OF MODERATE TEMPERATURE CURING COMPOSITE LAMINATES

GONG Zhi-hong, BAO Xiao, LI Jian-chuan, SU Jian

2017, 0(6): 85-88.

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In this paper, the delamination flaw samples of composite laminates were prepared by means of pre-buried quartz sand. The delamination flaw samples of composite laminates were repaired by the injecting repair method. The injection hole was punched with an electric drill in the side of sample of delamination flaw. The DG-8 adhesive was injected from the injection hole to delamination flaw area. The samples were heated to cure by the hot bonder. Mechanical property tests of the repaired samples were carried out. Nondestructive testing and microstructure analysis were also performed. The results showed that, tensile and compressive strength of repaired samples recovery rate was more than 85%, and the DG-8 adhesive of repair area achieved good curing condition.

THE RESEARCH AND DEVELOPMENT OF COMPOSITE LANDING GEAR FOR AN UNMANNED AERIAL VEHICLE (UAV)

ZHANG Guo-qi, HU Qi, WU Hai-sheng, GUAN Xin

2017, 0(6): 89-93.

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According to the main technical specifications for landing gear of an UAV, the composite foam sandwich is adopted based on the engineering formula and numerical simulation. In addition, the specific geometric parameter and stacking sequence are definitely determined. Furthermore, the specimen is fabricated by manual molding technology. The experimental results demonstrate that both the mechanical property and the weight of this specimen satisfy the requirement.

RESEARCH PROGRESS ON THERMOPLASTIC SIZING AGENT FOR CARBON FIBERS

LU Jia-teng, YAN Chun, XU Hai-bing, CHEN Gang

2017, 0(6): 94-99.

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Carbon fiber reinforced thermoplastics have been widely used in military and civilian industries, due to their excellent advantages such as toughness and impact resistance, long-term storage of prepregs, short molding cycle and easy recycling. Interface between resin and carbon fiber is one of the key factors to determine the properties of composites, and thermoplastic sizing agent is a critical obstacle that restricts the processing and performance of carbon fiber reinforced thermoplastics. This paper reviews the functions, types and preparation methods of thermoplastic sizing agents, including the interfacial interaction mechanisms between carbon fiber and thermoplastic matrix.

DEVELOPMENT OF INVESTIGATION ON MECHANICAL PROPERTIES OF 2D BRAIDED COMPOSITES TUBES

MA Xiao-hong, TAN Jiang-tao, QIN Zhi-gang

2017, 0(6): 100-103.

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Recent developments of investigation on mechanical properties of two dimensional (2D) braided composites tubes are reviewed at home and abroad, including the experimental study of mechanical properties, the structural geometric model and the numerical simulation research. In the experimental study, the energy absorption performance of 2D braided composites tubes and the effect of braiding angle on the mechanical properties of composites are emphasized. The study of the structural geometrical model focuses mainly on the microcosmic structures and macro-microcosmic structure model. Moreover, the popular modeling methods are also reviewed. In numerical simulation research, the solid model simulation analysis of 2D braided composites based on shaping theory and the orientation of the yarns are introduced. Finally, some problems in present studies are summarized and future investigation trends are proposed.

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