COMPOSITES SCIENCE AND ENGINEERING

DESIGN AND OPTIMIZATION OF FILAMENT-WOUND COMPOSITE OIL CASING PIPES

WANG Zhun, DENG Jing-lan, WANG Ji-hui, ZU Lei

2015, 0(5): 5-10.

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The winding angle of filament-wound composite oil casing pipes acts as an important technical index for controlling the mechanical properties of the oil pipes. The winding angle used in production can be calculated according to the netting theory. Without considering the effect of resin, the winding angle of theoretical calculation is not optimal;the fiber can not fully play its role in test and actual application. We use the finite element method to establish a numerical model with which we calculate and analyze the influence of different winding angles on the mechanical properties of petroleum casing, and predict the minimum burst pressure. Through comparing the effect of different winding angle on the mechanical properties of the winding composite pipe, we concluded that the optimum winding angle is 51°, and the minimum burst pressure of casing pipe 9-5/8 is significantly improved by 20.3% as compared to the burst pressure of winding composite pipe of which winding angle according to the theory of grid. The mechanical properties of the oil casing pipe are improved and there is a certain practical significance in engineering application of composite materials.

INVESTIGATION OF INFUSED EPOXY RESIN SYSTEM USED FOR LARGE SCALE CARBON FIBER REINFORCED PLASTICS

JIA Zhi-yuan, SONG Qiu-xiang, GUAN Xiao-fang

2015, 0(5): 11-15.

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Application of vacuum infusion molding technology for large-scalecarbon fiber composite material structure is an important developing direction of large-scale wind turbine blade manufacturing technology. Because the carbon fiber preform permeability is much lower than that of the glass fiber preform, epoxy resin with a special performance is a key for infusing large scale carbon fiber preform. This paper systematically studies pot life, curing behavior and mechanical properties of three kinds of typical epoxy resin system, and compared them with those of the common epoxy resin system for glass fiber. The analysis results show that, three kinds of special resins have pot life of varying lengths, but greater than the ordinary resin; building up properties of epoxy anhydride system is slow in the curing process, which is a risk in large-scale structure application; preform preheating contributes to the carbon fiber composite material which can obtain high fiber volume content and better mechanical properties.

RESEARCHES ON TENSILE PROPERTIES OF HPFRCC BASED ON ANALYSIS OF FOUR-POINT BENDING TEST

LIU Ze-jun, LIN Xin-yan, LI Yan

2015, 0(5): 16-20.

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Uniaxial Tensile Test (UTT) is internationally recognized as the most comprehensive test method which can display the tensile properties of HPFRCC, but the operation of UTT test is so complicated that it is inconvenient to take quality control in practice. According to the measured load-deflection curve of four-point bending test, section equilibrium conditions and stress and strain distribution, the calculating method on tensile properties of HPFRCC was established by evaluating four-point bending test results. The model assumes that the stress distribution of HPFRCC in compressive zone is linear and stress distribution in tensile zone is bilinear, which is in accordance with the performance of HPFRCC and is simple for calculating. Comparisons between the calculated and measured results indicate that proposed model is able to evaluate the tensile properties of HPFRCC, which provides an indirect analysis method on the tensile strength and ultimate tensile strain of HPFRCC for practical application.

THE WHOLE AND LOCAL FLEXURAL PERFORMANCE OF SANDWICH BEAMS WITH DIFFERENT FACE THICKNESS

ZHANG Fu-bin, LIU Wei-qing, QI Yu-jun, FANG Hai

2015, 0(5): 21-26.

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This paper presents the work on the whole and local flexural performance of sandwich beams with three different face thickness. First, three point bending tests were carried out to explore their flexural behavior. Test results show that, the failure mode of the sandwich beams concluded core indentation failure and core shear failure. Second, high-order theory base on variational principles was proposed to analyze the deflection and the strain distribution of the top and bottom faces at different location. Finally, analysis of failure load of the sandwich beams were conducted and gained good agreement with the experimental results.

INFLUENCE OF POLY (METHYL METHACRYLATE) (PMMA) ON THE CYANATE ESTER RESIN (BADCY) MECHANICAL PROPERTIES AND THERMAL PROPERTIES

HUANG Feng-ping, LI Chun-xue, ZHU Bao-lin, WANG Jun-long

2015, 0(5): 27-32.

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The materials were prepared on polymethyl methacrylate (PMMA) added into the bisphenol A type of cyanate ester resin (BADCy) by asynchronous synthesis method. The paper investigates the effects of weight of PMMA on the mechanical properties of the composites through flexural strength and fracture strength test and dynamic thermal mechanical analysis (DMA) testing,while using scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR). The results show that PMMA composite material flexural strength and fracture strength were the largest and increased by 58.5% and 88.3%, compared with pure BADCy. When the weight of PMMA is 20%, PMMA and BADCy react during the grafting reaction, eliminating the phase separation of epoxy resin and BADCy. The glass transition temperature (Tg) remains substantially unchanged, while the low viscosity of the composite, cast molding can be helpful. The thermal properties of composite was studied through thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC). The results show that weight loss temperature and mass retention rate were basically unchanged, while heat curing reduced the controllability of reaction, compared with pure BADCy.

ACOUSTIC EMMISION BEHAVIOR FOR ADHESIVE JOINTS OF METAL/GFRP CYLINDER-SHELL UNDER TORSION TEST

PANG Yan-rong, LIU Ran, ZHOU Wei, GONG Jing

2015, 0(5): 33-37.

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Acoustic emission (AE) testing technology was used to monitor the process of damage and failure of metal/GFRP cylinder-shell specimen under torsion test in real time. By experiment and numerical simulation, the effect of sizes of bolt and shell on torsional properties of adhesive joint of metal/GFRP cylinder-shell specimen and corresponding AE characteristics were studied. The results show that the load-time curve of cylinder-shell specimen is basically linear. It is found that cohesive failure is the dominant failure mode with fiber break and matrix crack. Increasing the diameter of bolt can effectively improve the torsional properties of metal/GFRP cylinder-shell. Besides, AE parameters are related to the damage and failure process. Higher AE amplitude, relative energy, during time and more cumulative hits are connected with the damage process of specimen with longer bolt diameter. Therefore, dynamic characteristics of AE signals can provide evidences for security evaluation of wind turbine blades roots.

THE PREPARATION OF 5228A EPOXY RESIN USED IN RFI AND THE IMPACTION ON MECHANICAL PROPERTY OF 5228A/CCF300 COMPOSITES

CHEN Wei, ZHANG Chen-qian, CHENG Li, LI Cha

2015, 0(5): 38-41.

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In this paper, the viscosity-temperature characteristics and formation property of 5228A epoxy resin used in RFI and the 5228A epoxy resin special used for prepreg are studied. Besides, the comparison of mechanical property between the two kinds of resins reinforced CCF300 composites are also studied. The results show that the 5228A epoxy resin system used in RFI which was prepared by proper modifying the formula of 5228A epoxy resin system special used for prepreg could meet the requirement of RFI. The impregnating-process temperature is 120~130℃ and the opening time is 60min. There are no obvious differences of the two kinds of resins reinforced CCF300 composites on the mechanical property.

EXPERIMENTAL STUDY OF THE FRP-FOAM SANDWICH TUBE UNDER AXIAL LOAD

XU Kang, DUAN Zhuang-zhi, SHEN Fen-fei

2015, 0(5): 42-46.

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Fiber-reinforced resin composite-foam sandwich pipe have better local flexural rigidity compared to the composite thin-walled tube. It had improved the local stability of the composite tubes greatly while weight increased less, which was similar to reinforcement ribs, thus giving full play to the strength of the material. In order to investigate the composite foam sandwich tube′s axial compressive performance of the different design parameters, the axial compressive experiment was studied in this paper. The results show that the fiber plies combination of the resin matrix composites foam sandwich tube has greater influence on the axial compressive performance and the different fiber ply combination can lead specimen damage from brittle failure to ductile failure. While the density of foam core layer has little influence on the ultimate axial compressive strength as it from 0.15g/cm³ to 0.45g/cm³. The paper gives the influence law of the different design parameters on the ultimate bearing capacity of the FRP-foam sandwich tube.

INVESTIGATION ON IMPACT PROPERTIES OF 2-D TRIAXIAL HYBRID-BRAID LAMINATED COMPOSITES

WANG Wen-sha, YAN Jian-hua, GU Hai-lin

2015, 0(5): 47-53.

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Three types of 2D triaxial carbon/glass hybrid-braid laminated composites with same laminating layers were designed to study the influences of hybrid-braid patterns on low velocity impact properties, providing basis for design and theory for applied reseach in aerospace and other fields. Through comparisons and analysis of low-velocity impact and three point bending experiments, we can conclude that: The composites of glass fiber as braiding yarn and carbon fiber as axial yarn, after low velocity impact, had the least cracks on the surface, the lowest absorbed energy per unit thickness, the minimum damage range in thickness direction, the minimum damage after bending experiment, thus the impact performance of this kind of composite was the best. Through suitable hybrid braiding patterns of carbon fiber/glass fiber combination, the impact properties can be effectively improved to achieve positive hybrid effect, and can enhance the impact performance of hybrid-braid laminated composites.

LOAD COMPARISON OF WIND TURBINE BLADE ROOT CONNECTIONS

SHI Jun-hu, LIN Ming, WU Sheng-jun, XIONG Gang

2015, 0(5): 54-60.

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The blade root connection of wind turbine is the only and most important component for connecting blade and hub. All the loads applied on the blade are transferred to the hub through the root connection, so the designs of root connection not only affect capacity of bearing loads, but also the length of blade. The targets are "T-type" connection and bushing connection, meanwhile take place research on the stresses of two different blade connections, providing evidences and guidance for the design work and optimization of blade root connection.

LARGE-SCALE COMPOSITE CURING TEMPERATURE ANALYSIS AND IMPROVEMENT IN AUTOCLAVE PROCESS

LIN Jia-guan, YANG Rui, WANG Tin-xia, ZHAN Dong

2015, 0(5): 61-65.

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The temperature field and flow distribution characteristics of the aero composite components in autoclave process, which based on the Fluent fluid analysis software, have been given in this paper. This work gives a method of fan installed on the frame type mold ventilation hole to enhance the thermal convection of air, and improve the uniformity of temperature field and flow distribution. The results show that, the flow field behind of frame type mold surface is complex, which has a flow vortex. Besides, the contact surface of composite has low temperature. However, the reasonable arrangement of fan position and control velocity can change the flow field inside the autoclave, make temperature uniformity of mold surface, and it is important to improve the curing temperature distribution uniformity of composite structure.

EXPERIMENTAL STUDY ON FLEXURAL BEHAVIOR OF GFRP COLUMNS

NIU Qiang-sheng, LIU Wei-qing, WANG Jun, WANG Xian-mei

2015, 0(5): 66-70.

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In this paper, 3 GFRP hollow cylinders and 3 GFRP cylinders filled with concrete were tested under the lateral bending. The load-displacement curve, the load-strain curve and the ultimate load of each specimen were obtained in the end. The test results show that, with the longitudinal-transverse ratio of fiber layers increasing, the ultimate load of both kinds of specimens and the bending stiffness of hollow specimens would be improved. However, it also indicates that the changes of fiber longitudinal-horizontal proportion have little influences on the specimens filled with concrete. What's more, with the length-to-diameter ratio decreasing, the ultimate load and the bending stiffness of both kinds of specimens would be improved, and the influence will become more evident for the specimens filled with concrete.

STUDY OF ADAPTABILITY OF VINYL ESTER RESIN SYSTEM FOR VARTM PROCESS

WANG Bao-chun, ZHENG Wei, XUE Ya-juan, WANG Xiao-bing

2015, 0(5): 71-75.

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By selecting vinyl ester resin as matrix resin, the effects of temperature and the content of diluent (MMA) on the viscosity of resin have been studied,finding the binary relation between viscosity, the content of diluent (MMA) and the temperature. The relationships of the content of different curing system and the rheological properties of the resin have been studied,and the flow performance of vinyl ester resin in the common fabric have also been studied, which has positive effect on the research of VARTM process.

PROCESS RESEARCH FOR IMPROVING QUALITY OF ROLLED ARAMID NON-WOOF CLOTH

LIU Yuan-kun, XU Dong-mei, AI Qing-song, FANG Xin-ling

2015, 0(5): 76-80.

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In this paper, several factors that affect the surface performance and bulletproof property of rolled aramid non-woof cloth were investigated, including tension of tow, adhesive, laminated composite temperature, pressure and speed. The optimum process conditions were defined by many experiments. When the tension of tow was 0.238 CN/dtex, the ratio of adhesive A,B and C was 100∶80∶5, the composite temperature, pressure and speed were 80℃, 2.5MPa and 5m/min, respectively. The rolled aramid non-woof cloth prepared had optimal comprehensive performance. The bulletproof chip prepared by the cloth passed the NIJ0101.06 and GA141-2010 standards testing. It shows that the process conditions have superiority.

DESIGN AND MANUFACTURE OF SILICA RUBBER PRESSURE MOLD FOR COMPOSITE MANUFACTURING

XIA Jing-yun

2015, 0(5): 81-84.

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Silica rubber pressure molding is one of a new composite molding process. The silica rubber mould and composite preprag are put together into a rigid outer tooling during manufacturing. The silica rubber mould will give pressure on preprag when it is heated. Because the pressure direction of silica rubber is changeable, it can produce many products which can't be produced by some traditional process such as molding or autoclave. This paper introduces the expansion pressure design and pressure detection of silica rubber pressure molding. This paper also introduces the design of casting tooling and transitive silica rubber mold.

CALCULATION RESEARCH ON WATER-SAVING SOLUTIONS OF DRY-WET CLOSED COOLING TOWER

ZHANG Li-xin, JI Xiang-yu, SHEN Yan, GAO Ming

2015, 0(5): 85-88.

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In windy and dusty areas short of water, with large temperature differences during one year, dry-wet closed cooling tower can be widely used in industry fields in order to achieve the best technical economy and the least water consumption. It operates as wet cooling tower in summer with water sprayed outside of pipes. While in winter, it operates as dry cooling tower without sprayed water. In spring and autumn, the way to save water is the mixed use of both dry and wet closed cooling tower, which can also achieve the cooling performance required.
In this paper, taking a project in Hami of Xinjiang for example, every single closed cooling tower is designed to be counterflow and coil stagger arranged whose structure is designed according to wet operating conditions while size in consideration of dry cooling required. Four different water-saving solutions and corresponding air consumption are given by calculating and clearly described. It is concluded that the fourth solution: four-month use of all cooling towers as dry coolers in winter, one-month use of all cooling towers as wet coolers in July and mixed use of dry and wet closed cooling tower in the rest months in a year leads to the least annual water consumption. The method and example mentioned above provide a reference to design and operation of dry-wet closed cooling towers.

THERMO-CHEMICAL BEHAVIOR OF PHENOLIC RESIN FOR RTM AND ITS COMPOSITES

LI Ting, LIU Jian-jun, YANG Xue-jun, ZHAO Wen-bin

2015, 0(5): 89-92.

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Thermal chemical behavior of a kind of phenolic resin for RTM process was studied, such as DSC, TG, Tg and viscosity-temperature characteristics. Based on the analysis of the process adaptability, carbon fiber needling preform reinforced the phenolic resin composites was made by RTM. Then the mechanical, thermal physical and ablative properties of the composites were tested and evaluated. Experimental results show that the interlayer shear strength of the composites is 32.4MPa, heat capacity of 200℃ is 1530J/(kg·K), linear expansion coefficient of 25~200℃ is -0.234×10^-6/℃, linear ablation rate is 0.069mm/s, quality ablation rate is 0.0926g/s. It shows good characteristics of thermal protection.

STUDIES ON PULL-OUT STRENGTH OF HONEYCOMB-STRUCTURE INSERTS IN HIGH TEMPERATURE

XU Wen-bin, LIU Zi-xian, YAN Zhen-yu, CHEN Jian-xiang

2015, 0(5): 93-96.

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The pull-out strength of honeycomb-structure inserts in room temperature and in high temperature were studied. The results were discussed and the effects of high temperature on inserts pull-out strength were analyzed. It was found that the normal pull-out strength of inserts in high temperature was reduce to about 8% of that in room temperature, and the failure mode is changed from shear failure of honeycomb to interface debonding of panel and honeycomb. It presents two typical failure modes when exerting parallel force on inserts in room temperature and in high temperature, respectively. The failure mode in room temperature is panel compression failure, while the failure mode in high temperature is panel instability failure, and the pull-out strength tested in high temperature reduces to about 28% of which tested in room temperature.

Industry information contents

2015, 0(5): 97-128.

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