Table of Content

28 January 2016, Volume 0 Issue 1

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BASIC STUDY

EFFECT OF LINER MATERIAL PROPERTIES ON THE AXIAL RESIDUAL DEFORMATION OF CARBON FIBER WOUND PRESSURE VESSEL

SHU Ming-jie, ZU Lei , WANG Ji-hui, LI Shu-xin

2016, 0(1):  5-9. 

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The investigation on axially residual deformation of filament wound pressure vessels has a great significance for improving the dimensional stability of the produced vessels and satisfying the pressure vessel certification. In this paper, the influence of the material properties of the titanium liner on the residual deformation of the isotensoid pressure vessel was evaluated. The accurate modeling method was used to create the cylindrical and dome sections for a helically and hoop overwound pressure vessel. The stress-strain curves of the titanium liners with various yield strength values were experimentally obtained and then substituted into the created finite element model. The axially residual deformation of the pressure vessels corresponding to various liner strengths was calculated. The results show that the filament wound pressure vessel became short in the axial direction after the given loading/unloading procedure. The change in the yield strength of the titanium liner has a remarkable effect on the axially residual deformation of filament wound pressure vessels.

EQUIVALENT MODELS RESEARCH AND NUMERICAL ANALYSIS OF PLATEFIN HEAT EXCHANGER SANDWICH PANELS

FENG Kun-cheng, LIU Bo, ZHANG En-yang

2016, 0(1):  10-16. 

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This paper aims to investigate the equivalent model of the metal sandwich structure of platefin heat exchanger, which is based on the small bending deformation theory and orthotropic sandwich panel bending deformation theory. The equivalent mechanical parameters of the metal sandwich structure of platefin heat exchanger can be derived by making the finite element equivalent model. Using finite element pretreatment software Patran, the platefin exchanger sandwich structure is simplified and separated into a representative unit. The strain components and bending forces of the representative unit are simulated under duplicate constraints. According to the constitutive relations of the stress and strain of the sandwich panel, the stiffness matrix can be simulated, and then the macroscopic equivalent elastic constants are derived. Using this method, the platefin heat exchanger sandwich panel can be equaled into a continuous singleboard unit. Finally the mechanical properties of the equivalent model are applied to the mode analysis of the platefin heat exchanger. Comparing with the mode test results, the rationality and effectiveness of the equivalent analysis method are demonstrated.

ELASTICITY ANALYTICAL SOLUTION OF SIMPLY SUPPORTED BEAMS STRENGTHENED WITH PRESTRESSED CFRP SHEET

CHEN Chao , ZHOU Ding , LIU Duo , ZHANG Jian-dong

2016, 0(1):  17-22. 

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Taking the simply supported beam strengthened with prestressed CFRP as an example, the effect of prestress value and layer number of CFRP on the stress and displacement distributions of the beam under static loads is studied. Firstly, the beams and CFRP sheets are considered separately. The beam is studied based on the two-dimensional elasticity. The CFRP sheet is analyzed by the string theory. Then, the unknown constants in expressions of displacements and stresses are obtained by the continuity of displacements and stresses between the beam and the CFRP sheet. Finally, the exact analytical solution of displacements and stresses in the beam are obtained. Comparing the results with those obtained from ANSYS shows the high precision of the present method. The results show that the prestressing sheet and the layer number of CFRP have important effects on the beam. The greater the prestressing force of CFRP and the more number of CFRP layers, the smaller stresses and displacements of the beam are.

STUDY ON THE VACUUM INFUSING POLYURETHANE FOR THE WIND TURBINE BLADE

JIA Zhi-yuan , GUAN Xiao-fang

2016, 0(1):  23-28. 

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In this paper, the vacuum infusing polyurethane resin, which aims at reducing the cost of the wind turbine blade, was studied. The results show that the resin system has the advantages of low initial viscosity, high feed rate, high toughness and good adhesion properties compared with the commonly used epoxy resin system. The application of this resin system to the main bearing structure of the wind turbine blade is made, and the production cost of the blade can be further reduced by increasing the fiber volume content.

CHARACTERIZATION OF INTERLAMINATE SHEAR PROPERTIES FOR COMPOSITE MATERIALS USING DIGITAL IMAGE CORRELATION

HAO Wen-feng, GUO Guang-ping, CHEN Xin-wen, WANG Xiang

2016, 0(1):  29-32. 

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Interlaminate shear strength is an important index for evaluation interlaminate mechanical properties of composite laminates. First, the short beam shear tests were carried out according to ASTM D 2344, and the interlaminate shear properties of CCF300/5228 composites were analyzed. Then, the full-field displacements and strains under different loads were obtained using digital image correlation (DIC) method. Finally, a finite element model of the composite laminate was built using ABAQUS, and the corresponding displacements and strains were extracted from the simulation. The simulation results were compared with the experimental results from DIC. The results show that the experimental full-field displacements and strains agree well with the simulation results. The distribution of full-field interlaminate strain of composite laminate can be monitored using DIC in real time. And, the failure location can be predicted from the full-field interlaminate strain. DIC method provids an effective tool for strain monitoring of interlaminate shear properties of composite laminates.

STRUCTURE OPTIMIZATION OF HEATED MANDREL BASED ON RESPONSE SURFACE METHODOLOGY

XU Jia-zhong , YUAN Ya-nan , GAO Liang-chao , YANG Hai

2016, 0(1):  33-39. 

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Heated mandrel winding is a new method which can achieve composite shell efficient winding. The temperature uniformity of heated mandrel surface is a very significant factor which influences the quality of the composite shell. In this paper, we select heated mandrel as the research object and take the location of mandrel little hole as the optimization variable. We design three factors three levels of test scheme based on Box-Behnken design methods. Then, based on this scheme, Fluent numerical simulation was carried out. Setting temperature trace points on mandrel and writing down the temperature value of these trace points, we calculate the temperature mean square error (MSE) and take MSE values as the response value. By fitting second order response surface equation, using statistical software Minitab to analyze the best position combination, and eventually, following the best scheme to do Fluent simulation, the results showed that model predicted values were in good agreements with simulation values. The temperature MSE of mandrel surface is only 1.96K and the temperature uniformity is good.

THE MATHEMATICAL MODELS AND STRUCTURAL SIMULATION FOR TWO STEP CIRCLE BRAIDED STRUCTURES

NING Fang-gang, YU Wei-dong

2016, 0(1):  40-44. 

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This paper developed the rose curve to generalized rose curve, and discussed the properties of rose curve and the effect of related parameters on the shape of generalized rose curve. Based on this discussion, this paper applied this generalized rose curve on the modeling of two step circle braided structures. The models could reflect the characterization and appearance of two step circle braided structure.

OPTIMIZATION DESIGN AND VERIFICATION OF COMPETITION WING STRUCTURE

LI Han-yang, DONG Guo-hua, YUAN Guo-qing

2016, 0(1):  45-50. 

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In order to make full use of the advantages of high strength and light weight of the composite materials, it is necessary to design the structure under the restriction of given design conditions. This paper took the wing of SAMPE super light composite competition as research object. According to the given configuration and work condition, we used the OptiSturct solver of Hypermesh to optimize a composite wing on structure, layer position, layer orientation and layer thickness. Considering the theoretical result and the manufacturing process, a kind of optimization design plan was given. Based on this design, material preparation and experiments were carried out. Hence, we made some improvement on the wing according to the result of experiments. Finally, we got the lightest wing which can satisfy the demand of load and displacement in the history of the contest.

APPLICATION REEARCH

ENERGY ABSORPTION CAPABILITY OF BRAIDED GLASS FIBER REINFORCED COMPOSITE TUBES WITH RECTANGULAR CROSS SECTION

XU Jing , MA Yan , YANG Yu-qiu

2016, 0(1):  51-57. 

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Composite materials are widely used owing to their light weight, excellent mechanical properties and high energy absorption capability. Previous studies show that energy absorption property of composite tubes with circular cross section is superior to the tubes with rectangular cross section. Consequently, most of current researches focused on tubes with circular cross section, while it is considered that the one with rectangular cross section could be more practically used in industry. In order to investigate the energy absorption capability of two dimensional (2D) braided and three dimensional (3D) glass fiber braided composite tubes with rectangular cross section, axial crushing performance were inducted with regard to braiding angle, and multi-micro fractures in the crushing process was observed by optical microscope to analyze the crush mechanism in this study. It was found that the central crack of D type tubes is shorter than that of T type tubes, which consequently lead to higher energy absorption value as shown in the result.

INFLUENCE OF THE IMPACT POSITION ON THE IMPACT PROPERTY OF THE SANDWICH COMPOSITE PANELS

YAN Xue-tong, JIA Li-xia , LIU Jun-mei, SHEN Xiao

2016, 0(1):  58-61. 

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The high-strength low-stretch industrial polyester filaments were used to manufacture the woven spacer fabric, which was filled with foam between the two surface layer. Then, the surface layer was composited with resin to make the sandwich composite panels. Impact test was performed at different positions on the composites and the sidewise compression property of the panels was tested before and after impacting to analyze the influence of impact positions on the impact property of the composite panels. The experiment results indicated that the visible impacting damage and side compression properties of panels after impacting were different when the impacting positions on the panels were different, even though the impacting energies were same. It was found that when the impact applied on the position of the binder yarn, the visible impacting damage was more obvious than that of the other positions. But the side compression loads of the panels impacted on the binder yarn were larger than that of panels impacted on other position.

DESIGN AND EXPERIMENTAL STUDY OF NEW MARINE COMPOSITE HIGH PRESSURE VESSEL

GONG Ke-zhuang

2016, 0(1):  62-66. 

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This study achieves development of new marine composite high pressure vessel, by reinforcing the in-service steel vessel using 10mm-thicknesss CFRC circumferencially. And hydrostatic test, blast test, and fitague test are carried out, referring to correlative standards. Results show that the composite materials share the hoop stress preferably, the blast pressre arrives 125MPa, and the vessel don’t break after 0~40MPa, 12000 times filling fatigue test. Experiments reveal that the composite vessel is designed reasonably, has high safe reliability, and it is a better technical method to develop the new marine high pressure vessel.

THE FABRICATION OF POWDER TACKIFIER FOR COMPOSITE PREFORM

GAO Long-fei, CHEN Ping, CHEN Ji-ping, SU Jia-zhi

2016, 0(1):  67-70. 

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One kind of powder sizing agent was prepared by Cycom890 resin. According to the rheology property, the prepolymerization temperature was setted at 150℃. The property of resin heated at different temperature was investigated. The results showed that the degree of cure and enthalpy change were approximately linear with the prepolymerization time. The softening point sharply rose when the prepolymerization time approached 2h. The best prepolymerization time was between 1.5h and 2h. In this condition, the resin was solid at room temperature and could be grinded to powder. The powder with low softening point was fit for composite powder sizing agent. The rheology curve of powder at 90℃ revealed that the using life was long.

WEIGHT REDUCTION OF A RADAR ANTENNA REFLECTOR

ZHANG Chen-hui, ZHANG Sheng, YANG Shang-jie

2016, 0(1):  71-73. 

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Chemical etching method is used to replace the original stretch of copper wire grid surface process in the project, high strength polyurethane foam, J-164 filled rubber and low density fiber powder are used to make antenna reflector flange and strengthening ribs. The method shortened the antenna production period, reduced the weight. The contour accuracy satisfies the drawing demands by using reasonable post-treatment process.

A REAL-TIME MONITORING METHOD FOR THE CHEMICAL SHRINKAGE IN THE CURING PROCESS OF EPOXY RESIN

YANG Xi, LI Shu-xin, WANG Ji-hui , HU Hai-xiao

2016, 0(1):  74-78. 

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Chemical shrinkage in the process of resin curing will cause composite material defects and these defects can greatly reduce the performance of the composite materials. According to this article, through the improvement method which adds a contrast bottle to the traditional capillary dilatometer as well as the selection of PE bag, a fast, efficient, high precision and high applicability test method of chemical shrinkage was found. Based on the contact of chemical shrinkage and degree of cure, it has been confirmed that the chemical shrinkage was independent with the temperature and time except for appearing only a bilinear relation with degree of cure. Overall, the line′s slope starts to change when the degree of cure is about 0.28 (initial gel point). The earlier stage slope is about 42.54. The later stage slope is about 64.63. The general chemical shrinkage rate is 7.55% after being completely cured. It also suggests that the rates of chemical shrinkage is greater after resin gelation.

STUDY ON CONTINUOUS BASALT FIBER REINFORCED WOOD COMPOSITE

SHI Yan-ling, JIA Tao-fang

2016, 0(1):  79-82. 

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Vacuum assisted resin infusion was used to manufacture the BFRP/wood composite with four different types of basalt fabric including plain 6×6, plain weave 9×9, twill 6×6 and twill 9×9. The different reinforcing effects were analyzed by testing the mechanical properties. The results show that the plain 6×6 BFRP/wood composite has the optimum mechanical properties.

THE SOLUTION FOR THE FAST BUILDING OF THE FEM MESH OF WIND TURBINE

HUANG Hui-xiu

2016, 0(1):  83-85. 

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In this aricle, we used the coordination data of wind blade 2D profiles and the position data of its major parts to create a set of effective solution of building the wind blade FEM mesh. Then, we built a special MATLAB program, which can build the mesh automatic very fast. In the program, the position of inner parts of blade is flexible, so a lot of time can be saved in later blade structure improvement and modification. The result shows that the blade FEM mesh can be used for calculation.

REVIEW

APPLICATION OF FIBER BRAGG GRATING ON CURE PROCESS RESEARCH OF ADVANCED COMPOSITE

ZHANG Yong-an, ZHAN Li-hua

2016, 0(1):  86-91. 

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Advanced polymer matrix composite is applied widely in the field of aerospace engineering. Autoclave molding process has became one of the primary molding process for composite structure, but this process exists problems of low efficiency and high cost, and the cure strain caused in forming process will affect the structure quality. By using FBG sensor to insitu monitor strain/stress, it plays an important role in making reasonable process and improving structure quality. In this paper, the solutions of crosssensitivity of FBG measurements in autoclave molding process are described in detail. The main research process of composite curing molding by using FBG insitu monitoring are reviewed during the past years. Combined with the research status at home and abroad, some considerations for the application prospect and urgent problems of FBG insitu monitoring are put forward.

APPLICATION OF HELIUM MASS SPECTRUM LEAK DETECTING TECHNOLOGY IN COMPOSITE MOLDING MOULD

WANG Lin, SU Jia-zhi, YAN Dong-xiu, WANG Jian

2016, 0(1):  92-96. 

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Helium mass spectrum leak detecting technology was introduced, and fabrication process of composite molding mould and vacuum integrity detecting methods for composite molding mould were discussed. The necessity of the application of helium mass spectrum leak detecting technology in composite molding mould was analyzed.This method had advantages in accuracy, economy, cycle, and so on. So it had a great meaning of applying helium mass spectrum leak detecting technology on vacuum integrity detecting test of composite molding mould. The application of helium mass spectrum leak detecting technology in domestic and foreign composite molding mould was introduced, the leak detecting system was designed, and some research and practices were developed. Also, some attentions during leak detecting test were summarized.