COMPOSITES SCIENCE AND ENGINEERING

THE SHORTER TIME PREDICTION METHOD OF LONG-TERM PROPERTY OF GFRP PIPES

LIANG Na, ZHU Si-rong, CHEN Jian-zhong

2017, 0(7): 5-9.

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The certification of glass-fiber reinforced plastic (GFRP) piping systems is regulated by normative standards in which test series of 10,000 h are needed to predict the residual property of the expected life (normally, 50 years). In this paper, the 1-4-4 combined optimal scheme for prediction of long-term property of GFRP pipe is proposed. This system involves using orthogonal design and test schemes lasting under 10,000 h. Experimental results for long-term ring-bending strain (S_b) of GFRP pipes from the standard test procedure indicate that this system is practical and effective. The estimation error when using the proposed method was consistently less than 5.24% as compared to the standard method.

PERFORMANCE ANALYSIS OF CARBON/GLASS HYBRID WOVEN UNIDIRECTIONAL COMPOSITE MATERIALS

GUAN Xiao-fang, JIA Zhi-yuan

2017, 0(7): 10-15.

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Carbon/glass hybrid woven unidirectional composite materials were studied for its use in wind blade in this article. Three kinds of carbon/glass hybrid woven unidirectional fabrics with carbon fiber mass content of 7.4%, 10.7%, 13.8% were fabricated into fiber reinforced composites. Mechanical properties and process properties of this kind of material were analyzed. The results indicate that, with the increase of carbon fiber content, 0° tensile strength, 0° tensile modulus and 0° compression modulus increased and 0° compression strength have no obvious variety regulation. After incorporation of carbon fiber, 90° tensile strength and modulus decreased. Low carbon fiber content of carbon/glass hybrid woven unidirectional fabric has good process performance considering its permeability in Z direction. In the future, this kind of new material is expected to play a role in weight loss and cost optimization for the wind blade.

INFLUENCE OF THE BLEEDERS ON THE RESIN FLOW DURING THE CONSOLIDATION OF RESIN MATRIX COMPOSITE STRUCTURES

HE Ji-lin, WANG Xiao-fei, MENG Yuan-ming

2017, 0(7): 16-21.

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The flow behavior of resin in the process of forming thermoset resin composites determines the volume distribution of the fiber after the final forming, which seriously affects the final forming quality of the components. As the absorption carrier of the excess resin in the prepreg, the material properties of the bleeder play an important role in the flow of the resin. Focusing on the bleeder, a simulation model is established for the consolidation and compaction of thick section composites in autoclave based on the AS4/3501 6 composite system. It contains solidification reaction module, heat conduction module and compaction module. Compared with the experiment data, the feasibility of the model was verified. The influence of the key parameters including porosity, permeability, and thickness on the flow of the resin under the synergistic action of pressure and temperature was studied by the simulation model. The results show that as the spatial measurement of the absorption resin carrier, the porosity and the thickness of the bleeder play a major role in the final compaction thickness of the composite laminates. The permeability of the bleeder influences the compaction by changing the resin flow rate. And, if the permeability is too small, the compaction thickness of the composite laminates would be decreased obviously.

PREPARATION AND MECHANICAL PROPERTIES OF CARBON NANOTUBE ALIGNED CARBON FIBER/EPOXY COMPOSITES

DONG Huai-bin, LI Chang-qing, REN Pan, ZHANG Wei-wei

2017, 0(7): 22-28.

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Carbon fiber/epoxy composites filled with carbon nanotubes were prepared by HF (high frequency electric field) induction method. The influence of the frequency on the mechanical properties of the composites was studied, and the microstructure of the composites was observed. The results show that the carbon nanotubes have obvious orderly alignment along the electric field in the resin-rich region. The interlaminar shear strength, compressive strength and flexural strength of the composite laminates can be increased by 28.9%, 28.83% and 15.01%, respectively. The surface roughness of the composites fracture surface increased with HF treatment, and the interface state of resin and carbon fiber was improved.

RESEARCH ON THE FLEXURAL BEHAVIOR OF CONCRETE SLABS WITH HYBRID REINFORCEMENT OF GFRP BARS

WANG Guo-qiang, SUN Li-xiang

2017, 0(7): 29-34.

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In order to study the flexural behavior of concrete slabs with GFRP bars, based on the the assumption of plane section, condition of internal force and deformation compatibility condition, the calculation formula of flexural capacity of GFRP reinforced concrete slabs under the two design cases of under-reinforced and proper amount of extra-reinforced is deduced. By the 8 groups of tests of GFRP slabs with different reinforcement ratio and concrete strength grade of concrete, the calculation formula of flexural capacity is verified. At the same time, the law between the variation of flexural capacity and reinforcement ratio, concrete strength is studied. The results show that the ultimate bearing capacity obtained by the experiment is in good agreement with the theoretical bearing capacity calculated by the formula, which can accurately reflect the calculation process of flexural strength of GFRP concrete slab. The failure mode of the design elements of the right amount of super reinforced concrete is destroyed by the crushing of concrete, which is more conducive to improving the safety performance of GFRP reinforced concrete slabs. At the same time, in order to ensure that the GFRP bar is not broken before the flexural capacity of concrete slab reach the maximum, it is proposing that the ratio of the balanced reinforcement ratio is of 1.4 times of the reinforcement ratio. With the increase of reinforcement ratio of GFRP reinforced concrete slab, the flexural capacity increases gradually, security reserves are also gradually increased. The flexural bearing capacity of GFRP reinforced concrete slab increases with the ratio of reinforcement ratio and concrete strength.

EXPERIMENTAL STUDY ON THE EFFECT OF STITCHING PROCESS ON THE MECHANICAL PROPERTIES OF COMPOSITES

WANG Fang-fang, ZHANG Fang-chao, WU Xiao-qing

2017, 0(7): 35-39.

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The effects of different stitch densities and different stitch thread thickness on the in-plane mechanical properties of carbon fiber eight-five-face satin-stitched composite materials were studied. The in-plane fiber waviness due to stitch thread implantation was measured by microscope observation, and the correlation between mechanical properties and in-plane fibers waviness was analyzed. The results show that the stitch has certain influence on the in-plane properties. As the stitch density becomes larger and the stitch thread becomes thicker, the in-plane mechanical properties show a decreasing trend and the decreasing range increases. Microscopic analysis shows that in-plane fiber waviness is characterized by the waviness amplitude and waviness angle in-plane, and the main factors that affect the mechanical properties of stitched laminates is in-plane fiber. Under the same stitch thread thickness, as the stitch density becomes dense, the waviness amplitude of the in-plane fiber is almost unchanged, and the waviness angle of the in-plane fiber increases first and then decreases, and the in-plane mechanical properties decrease as a whole. At the same stitch density, the waviness amplitude and angle of the in-plane fiber increased with the stitch thread thickness, and the decreasing trend of the strength had a strong correlation with the waviness amplitude and angle of the in-plane fiber, where the quadratic function correlation coefficient ranged from 0.89 to 0.97.

PROGRESSIVE DAMAGE ANALYSIS OF COMPOSITE BOLTED JOINTS

MEI Jun-jie, NI Ai-qing, WANG Ji-hui

2017, 0(7): 40-44.

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In order to investigate the combined influence of friction coefficient and bolt-torque on the strength of single-bolted composite joints and their mechanism, a three-dimensional finite element model of laminate in single-bolted joints has been built in ANSYS software. The bolted-torque is applied by using penetrative contact method. The influence of friction in components and secondary bending of the plates has been considered. The progressive damage analysis of composite bolted joints is implemented by using improved Hashin failure criterion and Camanho degradation model. The model is validated through comparison with experimental data in literature. It is shown that the joint strength can be enhanced by increasing the friction coefficient and applying appropriate bolt-torque. Increment in the bolt-torque cannot improve the joint strength obviously and higher bolt-torque can make the matrix crushing when the friction coefficient is small. Thus friction coefficient should be considered when applying bolt-torque. The results are instructive for engineering application.

INFLUENCE ON MECHANICAL PROPERTY OF ANGLE-INTERLOCK COMPOSITES BY LAYING-IN STRUCTURE

FENG Gu-yu, QIAN Kun, CAO Hai-jian, YU Ke-jing

2017, 0(7): 45-48.

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Two wovens with different organization structures were fabricated with the linear density of 2400 tex. The resin matrix was composed of epoxy resin E51 and polyether amine WHR-H023 in a mass ratio of 3∶1. The 3D curved shallow-crossing linking woven composite was then made from surface-treated reinforcement and resin matrix by VARI method. Universal Material Testing Machine was used to characterize the tensile properties of composites. The results show that, under the same compound technology, fiber volume fraction of the composites with laying-in is larger than those without laying-in. The composites with laying-in structure possess larger tensile stress and tensile model on both of warp and weft direction. The composites without laying-in structure possess larger tolerance of energy on both of warp and weft direction.

STUDY ON THE EFFECT OF ALKALI CORROSION ON THE PERFORMANCE OF BASALT FIBER ASPHALT

LI Li, LIU Zhao-hui, LIU Li, LI Sheng

2017, 0(7): 49-54.

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In order to enhance the reinforcement and strengthening effect of basalt fiber (BF) in asphalt, surface treatment of BF by 1.0 mol/L and 2.5 mol/L NaOH solution was performed. The surface morphology of BF was observed by environmental scanning electron microscopy (ESEM) and infrared spectroscopy (IR) test. The results show that the surface of original BF was smooth, and BF showed a clear core structure by NaOH solution treated from the ESEM. With the increase of NaOH solution concentration and treatment time, the results show that the higher the -OH content of BF is from the IR test. The basalt fiber asphalt of high, low temperature performance and drawing fracture morphology were studied, by softening point, 5 ℃ ductility, rutting factor and ESEM test. The results show that the higher the degree of erosion of BF by NaOH solution, the better the performance of basalt fiber asphalt. And, the best treatment time and concentration of NaOH solution for BF erosion were: 45 min, 2.5 mol/L.

AXIAL COMPRESSIVE PROPERTIES OF GLASS FIBER-REINFORCED POLYMER-MACROFOAM COMPOSITE COLUMNS

HE Wen-tao, WANG Jun, LIU Wei-qing, Li Meng-ting

2017, 0(7): 55-59.

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A series of axial compressive tests were conducted on two macrofoam columns and seven GFRP-Macrofoam columns. The failure modes, load-displacement curves and the characteristic of energy absorption of the tested specimens under compressive loads were presented. Influences of the numbers of GFRP layers, foam density and different horizontal fiber layer ratios were discussed herein. The test results show that with the using of GFRP, the deformation modes of columns change from the 45°-fracture to the typical three-stages. The carrying capacities, the total energy absorption and the specific energy absorption of specimens will increase as the layers of GFRP, foam density or horizontal fiber layer ratios increase. As the layers of GFRP increase from 0 to 2 and 4, respectively, the load capacity of specimens increases by 71.02% and 86.04% , and the energy absorption capacity are improved significantly. The density of macrofoam has a significant effect on stroke utilization. As the density increases, the stroke utilization decreases.

INFLUENCE OF COMPOSITE PATCH SIZE AND SHAPE ON LAMB WAVE DETECTION OF ALUMINUM PLATE REPAIR STRUCTURE

JI Zhi-xing, LI Cheng, TIE Ying, ZHAO Zhu-jun

2017, 0(7): 60-64.

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In order to study the influence of composite patch size and shape on lamb wave detection of aluminum plate repair structure, the structure models including piezoelectric transducers (PZTs) with the piezoelectric and inverse piezoelectric effect, aluminum plate, composite laminate patch and adhesive layer were established by means of ANSYS software. The lamb wave signal was excited and received in the models. Tests were used to verify the correctness of the model. The influence of damage on the propagation characteristics of Lamb wave in the structure was studied. The damage detection of the structure with composite patch was simulated to study the effect of different size and shape patches repairing the 8mm hole on the propagation characteristics. The simulation results of circular, square and rhombus patches show that different shapes have different effects on A₀ and S₀ wave packets. Rhombus patches of different sizes are also different for A₀ and S₀ wave packets.

MANUFACTURING OF CFRP ELECTRIC VEHICLE UPPER BODY WITH INTEGRATED STRUCTURE

YANG Yu-wei, TIAN Yu-li, LIU Xiao-xing, WANG Sheng-qi

2017, 0(7): 65-69.

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Based on the lightweight development requirements of a certain car model, an integrated carbon fiber reinforced plastic (CFRP) electric vehicle upper body was developed by performing structure design, CAE analysis and optimization and experimental verification. The results prove that, with reasonable structural design, CFRP is more suitable to be used as structural material in automotive applications. It can take significant effect of lightweight, and have potential development prospect in automotive field.

STUDY ON THE FORMING PROCESS OF COMPOSITES FILLED WITH NOMEX HONEYCOMB SANDWICH STRUCTURE

CHEN Wei, CHENG Li, YE Hong-jun, CHEN Jing

2017, 0(7): 70-73.

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In this paper, the edge dent is easily appeared in the curing process of bismaleimide resin matrix composite sandwich structure filled with Nomex honeycomb. The bismaleimide resin based carbon fiber laminate/honeycomb sandwich structures were developed by using different curing process, during which the co-curing process parameters were adjusted. The mechanical properties, internal quality and tensile properties of the sandwich structure were tested, based on which the influence of molding pressure on the sandwich structure quality was analyzed. The processing experiment shows that the edge dent of honeycomb core is mainly attributed to the local instable of honeycomb core resulted from the edge slipping of honeycomb core, during the cured process. It can be effectively solved by the method of step curing method and molding after bonded method of Nomex honeycomb core.

STUDY ON PULL-OFF LOAD OF SANDWICH STRUCTURE EMBEDDED GLASS FIBRE BOARD

LOU Cheng-fei, ZHANG Jin-kui, ZHANG Wei

2017, 0(7): 74-76.

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Sandwich structure is widely used in aircraft composite structures, and the mechanical properties of sandwich structures affect the integrity of aircraft structures. The test was carried out using glass fiber board G10-t0.25" embedded in carbon fiber material paper litter of core sandwich panel structure embedded parts, which have different diameters of 20 mm, 30 mm, and 40 mm. The results show that, compared with the typical metal post-embedded structure, the pull-off load is greatly improved. With the increase of embedded part diameter, the load of pull-off increases. However, the load of pull-off does not show significant change when the embedded part diameter is larger than 30 mm.

EFFECTS OF MODIFIER ON MECHANICAL PROPERTIES OF WGFRP/PP COMPOSITES

ZHANG Su-feng, LIU Yuan, XIU Hui-juan

2017, 0(7): 77-81.

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Polypropylene matrix composites(WGFRP/PP)filled with the Waste Glass Fiber Reinforced Plastics(WGFRP)debris was prepared by the banburying and mould pressing. The influences of WGFRP powder modified with silane coupling agents KH550, the amount of Modified Propylene Polymer (MAPP), Polyolefin elastomer (POE) to WGFRP/PP composite performance were studied. The results show that composite performance was enhanced a little with WGFRP powder modified with KH550, for which the tensile strength and flexural strength were increased by 28.63% and 20.13% with MAPP, respectively. The breaking elongation and impact strength were improved by POE, showing an increase of 152.36%, 45.43%, respectively. The SEM images show that the interfacial adhesion between WGFRP and PP is good by using agents. It presented improved performance macroscopically.

SIMULATION AND OPTIMIZATION OF RTM TECHNOLOGY FOR COMPOSITE "I" SECTION RIB PARTS

CHEN Ji-ping, SU Jia-zhi, HAN Xiao-yong, ZHENG Yi-zhu

2017, 0(7): 82-87.

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In this paper, we design the RTM manufacturing process of composite "I" section rib parts with PAM-RTM simulation. During the simulation process, we design 6 methods for manufacturing, considering infusion parameters, infusion ports and infusion types. Compare with simulation results including pressure distribution, resin permeation and infusion time of different methods, we get the optimum method. We manufacture the mold and the part after the simulation and comparison. The work and its results show that the position of "I" section rib affects the injection results including resin infiltration and efficiency less than injection port and mode selection. Line and root injection are better than point and tip injection. Simulation can help designing the molding of "I" section rib part and manufacturing instead of human-experiences to shorten the part manufacturing period and reduce the cost.

DEVELOPMENT OF AIRBORNE RADAR REFLECTOR ANTENNA BASED ON CARBON FIBER COMPOSITES

ZHANG Jian-ke, XU Lei, SHI Wei

2017, 0(7): 88-91.

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The structural characteristic of a certain type of radar reflector antenna was introduced in this paper briefly. Then, material selection, mould design, structure optimization, manufacture process were discussed and studied mainly based on antenna molding process. The mould surface was repaired by thermal compensation method. Simultaneously, the antenna curing parameters were optimized by orthogonal experimental design. The results demonstrate that the thickness of antenna can be controlled in the range of ±0.05 mm, the root mean square error (RMSE) of antenna surface is less than 0.1 mm, and the side lode level of antenna is able to reach -30 db (34.468 GHz), all of which can meet design requirement.

REVIEW ON SEISMIC PERFORMANCE OF FRP REINFORCED ENGINEERED CEMENTITIOUS COMPOSITE (ECC) FLEXURAL MEMBERS AND STRUCTURES

JIANG Shi-yong, TAO Shuai,LI Xue-yang

2017, 0(7): 92-99.

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Engineered Cementitious Composite (ECC) has excellent toughness, dissipation capacity and distribution of multiple cracking. Application of ECC can improve seismic ability of structures. Fiber reinforced polymer bars have the advantages of high tensile strength, lightweight and non-corrosive. The use of FRP reinforcement in combination with engineered cementitious composites (ECC) provides structural composite members with relatively large elastic deflection capacity and bearing capacity. The interfacial bond characteristics of the combination between FRP bars with ECC and the seismic performance of its structures are introduced. The results show that interaction of FRP bars and ECC matrix with ductile stress-strain behavior in tension results in nonlinear elastic flexural response characteristics with stable hysteretic behavior, small residual deformation. Finally the integrated performance index for evaluating the seismic performance of FRP bars combination with ECC structures are summarized, and the need for further research is proposed.

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