COMPOSITES SCIENCE AND ENGINEERING

ANALYSIS OF CURING TEMPERATURE FIELD AND THERMAL STRESS OF COMPOSITE LAMINATES UNDER DIFFERENT CONVECTIVE HEAT TRANSFER CONDITIONS

GU Wei, CHEN Shu-xian

2020, 0(1): 5-11.

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The physical model and mathematical model of the cure process of 3234/T300B composite laminates were constructed by finite element method. The solidification temperature field and thermal stress field of laminates under convective heat transfer conditions were numerically simulated. The effects of different convective heat transfer coefficient on the thermal stress during the cure process of the laminate and the residual thermal stress after curing were analyzed. The results show that the larger the convective heat transfer coefficient applied on the upper surface, the smaller the thermal stress inside the laminate during the heating process. And when the convective heat transfer coefficient increases from 5 W/(m²·K) to 10 W/(m²·K), the decline of the temperature and thermal stress is the largest. The research result shows that it is feasible to reduce the thermal stress and solidification residual stress of the laminate during the heating process by introducing convective heat transfer conditions, providing a parameter basis for optimizing the curing method using by air hot gun.

EXPERIMENTAL TESTING AND NUMERICAL SIMULATION ON FLEXURAL BEHAVIOR OF COMPOSITE GRID PANELS

WU Qi-fan, FANG Hai, GAO Feng, CHEN Ji-ye

2020, 0(1): 12-20.

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The paper aims to prepare a composite grid panel reinforced with glass fibre, including the pure grid panel with no skin, grid-stiffened panel with single skin and sandwich grid panel with double skins. By adopting the molding process, using unsaturated polyester resin as bulk material and glass fibre as reinforcer, the grid panel was manufactured. The flexural behavior of grid panel was investigated through experimental tests and numerical simulations. First of all, under three and four point bending loads, an experimental research was carried out to validate the effectiveness of the panels with different structural enhancement modes for increasing the ultimate bending strength and stiffness. The results showed that the flexural bearing capacity and bending stiffness can be significantly improved by strengthening the pure grid with upper skin, bringing the structure better ductile failure characteristics. Then, the numerical simulation of flexural behavior of the grid panel was conducted. The numerical results showed good agreement with the experimental results. Meanwhile, the effects of skin thickness, rib height, rib thickness and rib spacing on the flexural behavior of grid panel were analyzed.

PERFORMANCE STUDY AND FINITE ELEMENT ANALYSIS OF AUTOFRETTAGE PRESSURE OF THIN-WALLED METAL-LINED COMPOSITE GAS CYLINDERS

LIN Song, JIA Zi-xuan, LI Wen-bin, LI Shuang-wen

2020, 0(1): 21-26.

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The effect of autofrettage pressure on the performance of thin-walled metal lined composite cylinders was studied. The finite element method was used to simulate the autofrettage process of the cylinder, and the composite cylinders were wound to verify the hydraulic fatigue and blasting test. Besides, the acoustic emission monitoring was introduced into the test process. The experimental and analytical results show that the autofrettage pressure had great influence on the fatigue and blasting performance of thin-walled metal lined composite cylinders. The excessive autofrettage pressure would lead to resin cracking and fiber breakage in the composite layer of gas cylinder, which would reduce the burst pressure strength of composite gas cylinder. The fatigue test results show that excessive autofrettage pressure could easily lead to the lining to enter the yield state ahead of time and reduce the fatigue life. For thin-walled metal lined composite cylinders, the selection of autofrettage pressure should fully consider the stress of metal lined cylinders in autofrettage and working process, so as to make them in a reasonable range.

FINE MODELING OF AIRCRAFT RADOME ROOT CONSTRAINTS

QU Xiu-xiao, LI Xing-de, ZHOU Chun-ping, WANG Jia-xian

2020, 0(1): 27-32.

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Radome wall structures are often sandwich type limited by electrical performance designs, where the radome is mounted onto aircraft fuselage thorugh the use of rubber sealer, hinge, and limited numbers of coin pins and locks. The radome is also required to undertake aerodynamic loads. Thin wall sandwich structures is wick in undertaking pressure loads, while the root constraints is very stiff and can undertake large loads, which conseqnently influence the stress distribution of the radome. Correct modeling of the root constrains will yield correct stress fields on the radome. This paper uses segmented linear, non-linear tracing modeling, result reverse calculation and test verification to raise and substantiate a detailed modeling method of radome root constraint. This paper takes a certain radome as an example, and conducts FEM modeling around the requirement of NASTRAN software that uses on other modeling approaches. The present method is proved to be a reliable way to the detailed modeling of radome constraint.

FINITE ELEMENT SIMULATION ANALYSIS OF ROTOR COMPOSITE BLADE DAMAGE UNDER BULLET IMPACT

LI Xiao-bin, FANG Ke, SHEN Ya-juan

2020, 0(1): 33-38.

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In order to investigate the damage of helicopter rotor blade under high speed bullet hitting, the FEM was used to analyze the rotor blade impact damage. The finite element model of composite blade is built based on ABAQUS, applying the 3D composite failure criterion based Hashin criteria to judge the ballistic damage and stiffness reduction. Through the FEM simulation results, the ballistic damage of the blade can be observed visually. Compared with the experimental results, the accuracy and validity of the results are proved. The simulation analysis of the blade ballistic under different conditions is carried out, which can predict the blade ballistic damage and provide some reference for the against-ballistic design of blade structure.

EFFECT OF INFRARED HEATING WINDING FORMING PROCESS PARAMETERS ON INTERLAMINAR SHEAR PROPERTIES OF CF/PEEK COMPOSITES

SHAN Hao, CHEN Yu, LI Jun-jie, YAO Qian

2020, 0(1): 39-46.

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In order to manufacture continuous carbon fiber reinforced polyetheretherketone composites (CF/PEEK) winding product with excellent interlayer adhesion performance, the CF/PEEK unidirectional tape prepared by powder impregnation process was used as raw material, and the winding forming process was studied by using a self-made high-power infrared heating thermoplastic composite winding forming equipment. The quality of the winding products were evaluated by testing the interlaminar shear strength. The effects of key process parameters such as feed tension, compaction force, winding rate, winding temperature, preheating time and cooling rate on the performance of CF/PEEK ring products were studied. The results showed that the winding products had an excellent performance manufactured under the optimal condition as follow: molding temperature 410 ℃, preheating for 45 minutes, feeding tension 8 kg, cylinder pressure of roller 0.30 MPa, mandrel rotating speed 6 r/min, and slow cooling condition. The interlaminar shear strength of the prepared CF/PEEK ring was up to 82.29 MPa. Based on the above research results, the CF/PEEK winding pipe was prepared.

EFFECT OF REDUCTION DEGREE ON MICROWAVE ABSORPTION PROPERTIES OF GRAPHENE COMPOSITES

ZOU Yi, WANG Jun, TIAN Xu-jun

2020, 0(1): 47-51.

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Reduced Graphene Oxide (RGO) is considered to be the most promising candidate for high-efficiencyelectromagnetic wave absorption materials. The dielectric loss mechanism associated with its defects is a hot topic in current research. Graphene Oxide (GO) was prepared by closed oxidation method, and RGO with controllable reduction degree was prepared by VC reduction. The results show that the reduction degree of RGO increases with the increase of the amount of VC and the conductivity is positively correlated with it. Highly reduction degree RGO has better absorbing property in 1 GHz~18 GHz. When the addition amount of RGO is only 1.5wt% in the resin matrix, the absorber with 3 mm thickness has the strongest absorption peak of -16.4 dB at 9.5 GHz. This work reveals the dielectric relaxation mechanism related to RGO defects, and provides an understanding for the research and application of novel graphene-based composite absorbers.

STUDY ON THE EFFECT OF MECHANICAL PERFORMANCE FOR STITCHED COMPOSITES BY STITCHING PARAMETERS

YANG Long-ying, GONG Jia-qian, HUANG Dang-ming

2020, 0(1): 52-59.

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The stitched composite was popular in the field of aeronautics and astronautics because of the excellent property of impact resistance. The different stitching parameters such as stitch pressure, stitch pitch and stitch spacing could be set in the stitching process, and different stitching parameters had different effects on the mechanical performance of stitched composites. In this article, the effects on mechanical properties such as tensile property, compressed property and shearing property of stitched composites by different stitch pitch and stitch spacing for chained stitching and truffing were studied, so as to ascertain the best stitch pitch and stich spacing for the chained stitching and truffing.

610B HALOGEN-FREE FLAME-RETARDANT EPOXY RESIN AND PROPERTIES OF CARBON FIBER REINFORCED COMPOSITES

ZHOU Yu, LUAN Yi-hao, ZANG Qian, LING Hui

2020, 0(1): 60-66.

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A new kind of phospho-silicon synergistic halogen-free flame-retardant epoxy resin 610B was designed, and the hot-melt prepreg T700/610B was prepared. DSC, gel time, dynamic viscosity, TGA, IR and SEM were used to study the reaction and rheological characteristics of the resin system, the storage period at room temperature and the mechanism of the flame retardant. Carbon fiber reinforced composites were prepared through vacuum bag only forming process, and mechanical properties and flame-retardant properties were evaluated. The results show that the resin can be cured under medium temperature condition, and its storage life at room temperature is more than 30 days. The prepreg shows good processability, and suitable for the low-cost vacuum bag only molding. The composite shows outstanding flame-retardant performance of low smoke and low toxicity, as well as excellent mechanical performance.

VERIFICATION METHOD FOR COMPOSITE KEEL STRUCTURE OF AIRSHIP TRUSS BASED ON BUILDING BLOCKS

LI Yuan-zhang, LU Guo-fu, REN San-yuan, XIAO Peng

2020, 0(1): 67-71.

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In order to obtain the identification method of airship composite keel structure, according to building block approach for composite structure, with the consideration of the structural feature of airship truss keel, the certification way and detailed procedures of structure design and strength verification of the keel of airship truss composite are presented in this paper. By using this method, the structure strength of composite materials truss keel of a certain type of airship is tested and verified from element level to component level to full size keel, and the finite element analysis and its results are compared and analyzed. Some typical tests and analyses are selected and introduced. The results show that the Nastran finite element analysis model of truss composite structure meets the engineering needs. Airship truss composite keel can be verified by building block method.

STUDY ON PROPERTIES OF A HYBRID UV-CURABLE PREPREG FOR OIL TANKS

QIAN Jian-hua, CHEN Ling, LIU Shi-qiang

2020, 0(1): 72-75.

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The factors affecting hybrid UV prepreg were analyzed. The test proved that the curing thickness of the prepreg was positively correlated with the concentration of thermal initiator. When the concentration of thermal initiator (BPO) added was 1.0%, the maximum curable depth was 30.4 mm. When the concentration of thickener (MK 35) was 1.5%~2.0%, the thicking curve was most suitable. The properties between traditional UV prepreg and hybrid UV prepreg were compared. The test proved that the mechanical properties were comparable, while one-time curing depth of hybrid UV prepreg was 120.3% higher than traditional UV prepreg, which solves the problem of limited thickness of UV prepreg.

PREPARATION AND MECHANICAL PROPERTIES OF CF/PPS KNITTED COMPOSITES

ZHANG Jia-xin, MEI Qi-lin

2020, 0(1): 76-81.

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CF/PPS was prepared by blending method,and continuous carbon fiber reinforced polyphenylene sulfide composite laminates were prepared by moulding process. The effects of layers, hot pressing temperature, hot pressing time, resin content and silane coupling agents on the mechanical properties of composite laminates were studied. Carbon fibers and composite laminates were characterized by universal material testing machine, scanning electron microscopy and SEM-EDS. The results show that the optimum technological conditions of carbon fiber reinforced polyphenylene sulfide composite laminates are as follows: the number of layers is 20, the hot pressing temperature is 330 ℃, the hot pressing time is 30 min, and the resin mass fraction is 50.2%. The mechanical properties of composite laminates are significantly improved after being treated with silane coupling agent KH560, and their tensile strength and flexural strength are 920.1 MPa and 890.6 MPa, respectively.

PARAMETERIZED FEM MODEL GENERATION OF WIND TURBINE BLADE

QI Pei-yu

2020, 0(1): 82-86.

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When wind turbine blade becomes bigger and bigger, we need more optimization of blade design which requires fast generation of FEM model. The parameterized method could generate blade model quickly and accurately, which is explored in this paper. From aerodynamic design, the aerofoil data, blade shape layout, component positioning data, material performance, lamination plan and etc information are parameterized. After research, we can calculate the nodes, elements and lay-out data required by FEM model. Finally, the formatted data for FEM software could be generated automatically.

STUDY ON CONTROLLING THE DEFORMATION OF COMPOSITE FUSELAGE Z-SHAPED FRAME

HAN Xiao-yong, SU Jia-zhi, WANG Lin, GAO Long-fei

2020, 0(1): 87-91.

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Z-shaped frame was laid-up and cured on the lay-up & curing tooling using unidirectional prepreg. The profile of part was measured by coordination measurement mechine (CMM), this paper analyzed the deformation of Z-shaped frame according to comparision measuring data of the part with theoretical profile of the part. The deformation contains springback between inner & outer flange and web of the part, deformation in the radius direction and deformation in the web direction of the part. Using the surface of frame which was compensated according to the part′s acceptance document to modify the design of curing tooling, a full-scale part was manufactured on curing tooling which has been compensated. The part was measured by CMM again, the result showed the validation of compensation to curing tooling surface, surface profile tolerance of the part conformed to the part′s acceptance document (±0.375 mm). Z-shaped frame matched shear tie and skin perfect when it was assembled.

STUDY ON IMPACT RESISTANCE OF BASALT FILAMENT/ARAMID INTERVAL YARN FABRIC COMPOSITE SHEET

WANG Zi-shuai, ZHONG Zhi-li, WAN Jia, XUE Zhao-lei

2020, 0(1): 92-94.

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The impact resistance of basalt filament/aramid spacer fabric composite plates with different warp fineness and warp density were tested with the same impact energy. However, for the prefabricated pieces with the same longitude fineness and other parameters, the density of the prefabricated pieces increases, and the impact resistance of the basalt filament/aramid spacer fabric composite plate weakens.

THE EFFECT OF HOLLOW GLASS MICROSPHERES ON PROPERTIES OF EXPANDED FLAME RETARDANT SILICONE RUBBER COMPOSITES

XIE Chao, QIN Yan, HUANG Zhi-xiong, ZHANG Bo-wen

2020, 0(1): 95-100.

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With hollow glass microspheres (HGM), composite expansion flame retardant melamine polyphosphate (MPP)/pentaerythritol (PER), synergistic flame retardant aluminum hydroxide Al(OH)₃, condensation type room temperature vulcanization, the liquid silicone rubber (107 glue) was made into a HGM filled type expanded flame retardant silicone rubber. The effect of the loading of HGM on the properties of the expanded flame retardant silicone rubber composite was investigated. The results show that with the increase of HGM content, the tensile strength of silicone rubber composites increases first and then decreases, the elongation at break decreases gradually, and the density decreases, and the backside temperature decreases gradually and then rises slightly. When the HGM content is added to 30wt%, the oxygen index of the silicone rubber expanded flame retardant composite reaches 36, and the thermal conductivity value achieves the lowest value of 0.15 W·m^-1·K^-1, which demonstrates that the optimal filling amount of HGM is 30wt%.

COMPARISON OF TWO METHODS FOR RESIN CONTENT MEASUREMENT AND UNCERTAINTY OF GLASS FIBER PREPREG

LV Hui, LIU Xia, ZHANG Kun, GONG Wei

2020, 0(1): 101-107.

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In the production process, resin content has an important influence on the performance of glass fiber prepreg and the resin content of the prepreg measured by different test methods will also vary. In this study, four batches of high silica/phenolic plastics prepregs were tested by dissolution method and burning method. The Dixon criterion was used to eliminate the outliers and the uncertainty was evaluated for each set of data. The test results show that the value of resin content determined by dissolution method is lower, which may be caused by incomplete elution of the dissolved resin, and the uncertainty of resin content determined by burning method is smaller, which shows that test result of the burning method is more stable. In order to make the test results more accurate, burning method should be chosen.

NEW PROGRESS IN RESEARCH ON RC BEAMS STRENGTHENED WITH FRP STRIPS/SHEETS

WANG Yi-xin, WANG Xi-cheng, A Lata, WANG Xing-guo

2020, 0(1): 108-113.

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As one of the main force-receiving members in reinforced concrete structure system, reinforced concrete (RC) beams often break or affect structural safety because of various reasons. As a new type of structural material, FRP has been widely used in practical RC beams reinforcement engineering with its light-weight, high-strength and corrosion resistance. At present, the research on FRP reinforced RC beams is more in-depth. This paper has compiled the research status of the static performance, fire resistance and impact resistance of FRP-strengthened RC beams by domestic and foreign scholars, analyzes the problems existing in the current research, and puts forward suggestions for future research directions.

REVIEW OF THE VIBRATION CHARACTERISTICS OF COMPOSITE LAMINATED PLATES

LUO Ying-qin, LI Hua-dong, HONG Ming

2020, 0(1): 114-119.

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As an inherent property of the structure, the vibration characteristics are closely related to its function and application. The designability of composite laminates offers great potential for designing the vibration performance. As the application range of composite laminates becomes more and more widely especially in military applications, the related vibration problems are also attracting many researcher′s attention. It is extremely important to study the vibration characteristics of composite laminates. It is necessary to analyze the essential mechanism of actual vibration problems from the theoretical study of the vibration characteristics of composite laminates. So the theory for composite laminated plates are overviewed firstly. Then the domestic literature about the vibration characteristics of composite laminated plates are classified. The research of inherent vibration characteristics of the typical laminated structures including laminates, reinforced laminates, damping laminates and other special laminates are summed up, summarizing the current problems and future development directions and providing a useful reference for related studies.

PROSPECT FOR THE APPLICATION OF THREE-DIMENSIONAL CONSTITUTIVE CHARACTERIZATION TECHNIQUE FOR THICK-SECTION LAMINATED COMPOSITES

CHEN Guang-chang, WANG Ya-na, CHEN Pu-hui

2020, 0(1): 120-126.

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There is no unified standard test method for the three-dimensional mechanical properties of the thick-section laminated composite materials. Accurate and efficient characterization of the three-dimensional mechanical properties of composite materials, especially the complete stress-strain curve, is critical for understanding the complex deformation and failure mechanisms of composites, especially for the glass-fiber and carbon-fiber reinforced polymer matrix composites which play a critical role in aviation structures. In this paper, the latest progress in characterization of three-dimensional constitutive relations of laminated composites abroad is introduced, and a new method of assessing modulus and strength in three directions and non-linear shear stress-strain curves in three main material planes of composites, which is based on the short beam shear and small rectangular plate torsion specimens and full-field deformation obtained with the digital image correlation method. In addition, the state-of-the-art status of technology in three-dimensional constitutive relationship characterization of thick cross-section laminated composites in China, and caps between the civil and western are summarized as well. The overview shows that the correspondences of stress and strain filed in digital image correlation measurement and the inverse of the material constitutive properties based on the digital image correlation strain measurements are the key techniques needed to break through in order to obtain accurate measurement of three-dimensional mechanical properties of composites.

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