08 March 2013, Volume 31 Issue 7

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    Spescial Issues
  • JIAO Weicheng;YANG Fan;HAO Lifeng;XU Zhonghai;LIU Wenbo;WANG Rongguo;HE Xiaodong
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    In the development of the new energy cars, the rocket engine systems and the satellites, there are some special requirements, such as the high air tightness, the lightweight and the long-life, for the composite pressure vessels used to store the liquid propellant and high pressure gas. In this paper, a new method is proposed to design and prepare the lightweight composite pressure vessels with ultra thin metal liner. A characterization method for the slippage coefficient measurement between the fiber and the mandrel is developed. The Al alloy liners of 0.8mm in thickness are fabricated. A new stronger interface between the composite layer and the ultra thin Al alloy liner is designed according to the structure of the Gecko feet. A Self-healing technology is adopted to improve the reusable properties. With the lightweight composite pressure vessels, the weight can be saved by 70% as compared to the metal pressure vessels with the same volume and the same pressure.
  • YE Jinrui;LI Jia;LIU Weiping;ZHANG Boming
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    With a carbon fiber reinforced epoxy resin composite structure as an example, this paper studies the influence of the delamitation flaw on the compressive strength. The typical test pieces with preset delamitation flaws and the related test facilities were designed to test the compressive strength. The effects of the location and the size of the delamitation flaw are studied by numerical simulations combined with experiments. It is shown that the position of the delamitation flaw affects the delamitation form of the laminate and the small scale delamitation flaws do not affect the compressive strength. This conclusion is useful for the design and manufacture of the aircraft structures.
  • LIU Sui;GUAN Zhidong;GUO Xia;YAN Dongxiu;LIU Weiping;KONG Jiaoyue
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    Three different repair methods were adopted in the paper to restore the mechanical performance of composite honeycomb sandwich panels with different initial damages, and an experimental study was conducted to compare the edgewise compressive capacities of repaired specimens. Test results demonstrate that all these repair methods can recover the edgewise compressive strength of specimens effectively, and the strength recoveries are all above 79% of the intact panel level. The panel with the smallest initial damage has the highest strength recovery. Besides, unsymmetrical repair structures should be adopted cautiously to avoid the mechanical performance degradation induced by the additional bending moment. Based on test results, a finite element model was adopted to investigate the edgewise compressive behavior of repaired specimen. The calculated stiffness, ultimate load and failure model are in good agreement with test results. The numerical model provides an efficient repair design method on composite honeycomb sandwich panels.
  • LIU Xin;WU Zhanjun;WANG Rongguo;LIU Wenbo;YAN Jia
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    The triangle cross-section carbon fiber reinforced plastics could be used as absorbing composite materials, in which the incident microwave can be reflected many times to be greatly attenuated. The microwave absorbing property is affected significantly by the distribution of the triangle cross-section carbon fibers in the composite materials. In this study, the distribution of the triangle cross-section carbon fibers in the triangle cross-section carbon fiber reinforced plastics is investigated by experimental and theoretical simulations. In order to study the angle arrangement and the homogeneity of the carbon fibers in the composite materials, the cross-section morphology of the samples is observed by the SEM. And a process based on the Monte Carlo Method is established to simulate the distribution of the triangle cross-section carbon fibers in the triangle cross-section carbon fibers reinforced plastics. The simulation results agree with the experimental data, which indicates that the triangle cross-section carbon fibers are arranged in a random in angles and approximately homogeneous distribution. This simulation method could be used to simulate the cross-section morphology of the triangle cross-section carbon fibers reinforced plastics with arbitrary fiber contents.
  • GUO Xia;GUAN Zhidong;LIU Sui;KONG Jiaoyue;YAN Dongxiu;QIAO Liuping
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    The tensile performance of the adhesive-bonded single-lap composite joints is studied by the finite element modeling. The effect of the lap length on the tensile properties is analyzed with respect to the stress distribution and the failure mode. It is shown that: when the lap length changes from 5mm to 45mm, the minimum shear stress gradually decreases; when the lap length is greater than 20mm, the effect of the lap length on the stress distribution is decreased; the failure load increases gradually with the lap length; the increase rate is reduced when the lap length is greater than 20mm; the failure mode of a single lap joint is to start from the edge of the adhesive -composite interface, and then the adhesive damage. The lap length affects the damage level.
  • XU Longtao;WU Zhanjun;WANG Yishou;MA Shuyi
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    When composites structures are impacted by an external low-velocity object, it is easy to cause the subsurface damage yet undetectable by visual inspection. These damages will reduce structural bearing capacity. In this paper, an experimental study was conducted on a cylindrical stiffened composite structure to investigate several key issues on impact load identification based on system identification method. Firstly, the selection principle of the model order of the transfer function was discussed and clarified to improve the performance. Furthermore, to overcome the limitation that the homogeneity of sensor responses is not ensured due to the manufacturing and installation process of piezoelectric sensors, a sensor signal correction method was proposed in order to improve the accuracy of force identification. At last, the influence of stiffeners on the impact identification techniques was analyzed and discussed. The experimental results indicated that the method can be feasible for improving the identification and reconstruction of external discrete impact force on cylindrical stiffened composite structures.
  • SUN Xiaowei;LI Yanbo
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    Slag and coal gangue are used as supplementary cementing materials in the blend cement, and the effect of the fineness and the blend ratio of slag and coal gangue on the strength of the blend cement is studied. With the strength of the cement mortar as the parameter, the best composite system is identified. It is shown that for the composite system consisting of slag and natural gangue, the slag fineness determines the strength of the composite cement, the finer the slag, the higher the strength of the blend cement. With a given total amount of slag and natural coal gangue as the mixed material to replace the cement aggregates, the composite cement strength increases with the increase of the slag proportion and with the decrease of the gangue proportion. The natural coal gangue is not active, and the activity is only shown after calcination.
  • CHEN Qi;GUAN Zhidong;LI Zengshan
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    GLARE (glass-reinforced aluminum laminate) is a new kind of hybrid materials, used in advanced aircraft. This paper gives a brief overview of the history of fiber metal laminates, the manufacturing processes of GLARE and commercially available GLARE grades. Special attention of the review is paid to the following areas, mechanical properties, impact resistance, bearing resistance, fatigue resistance, residual strength, environment durability, inspection and repair of GLARE. Some urgent research topics are pointed out, including the mechanical tests, the modeling of crack growth and the residual strength of GLARE under hygrothermal environment.
  • Articles
  • CHEN Yuanjiang;YIN Jin
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    Based on the Analytic Hierarchy Process (AHP) and the ideal point method (TOPSIS), the mathematical model for optimization of the mining method is established. In the mathematical model, the Delphi method (the expert opinion method) is used to determine the mining method's optimal sort of the decision-making indicators, such as the angle, the thickness and the roof soundness. First, the candidate program indicators are put into the judgment matrix, through the AHP, the weight of each index is determined in the judgment matrix. Then, the sorting is optimized by the ideal point method, to obtain the weighted standardized decision-making matrix. Finally, the relative closeness of the schemes is obtained by the ideal point method, The synthetic superior degree of mining methods in Sanshandao Gold Mine are 0.1467, 0.5168, 0.9706, and the third mining model is in the first place, which verifies the feasibility of the model, to serve as an effective reference for the optimization of mining methods.
  • LI Baolong;WANG Dandan;ZHU Dequan;YU Xiaoge;FAN Haibin
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    Gejiu tin-copper polymetallic ore deposit located in Yunnan Province is one of the largest tin ore districts in the world, comprising of Malage, Songshujiao, Gaosong, Laochang, and Kafang ore fields. There are two kinds of ore-bodies in Kafang copper deposit. One is stratiform-like ore-body, and the other is contact skarn ore-body. This deposit has been known as the Yanshanian granite-related deposit for long time, however recently some researches argue that it is a syngenetic deposit formed by marine exhalation or it is a basalt-related. The Kafang and Laochang basalt type copper deposit is selected as the main study object. In order to reveal the ore-hosting structural development patterns and its geological implication, the measurement and statistical analysis on the ore-hosting or ore-controlling structures developed in granite, basalt, and marble are studied. It shows that the basalt type copper deposit mainly controlled by the N-S direction, E-W direction, and NE trending structures, and especially the NW trending structures should be given more attention than ever before. The ore-hosting structural space is also controlled by these structures. The results will provide an important evidence for the genetic type establishment of Kafang and Laochang basalt copper deposit, and give a guide to the next exploration of ore resources.
  • YUAN Junliang;DENG Jingen;LI Dahua;CHENG Lijun;YAN Wei;HU Lianbo;LIN Hai
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    Drilling and exploitation of the gas shale is just in an initial stage in China. Drilling practice shows that drilling accidents are frequent, and major cause is wellbore instability. From the experience of the shale-gas drilling in North America, and the casing programs in Sichuan Basin and Haynesville, it is shown that the drilling accidents can be reduced by the decrease of the size of the borehole. Based on the size effect theory, the advantages and disadvantages of different size effect models are compared. The Vutukuri's model is chosen to analyze the micro-borehole surrounding rock strength and the Mclamore's anisotropic failure prediction model is adopted to demonstrate the strength anisotropy of the shale. Based on the collapse pressure prediction model, the collapse pressure of a normal borehole and a micro-borehole in the bedding formations are calculated, respectively, furthermore, the trajectory sensitivity analysis is also conducted. The collapse pressure changes with the well declination are also considered. Comparing the difference between the two sides, it is shown that the micro-borehole can significantly reduce the collapse pressure by approximately 10%, therefore reduce the shale-gas drilling accidents.
  • Reviews
  • YANG Mingqing;QIN Liming;FU Lixia
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    Continuous Basalt Fibre (CBF) is a new type of materials which has been applied to many fields, including national defense, industry, and civil usage. In recent years, Russia and other countries have made pipes from CBF and used them to oil industry successfully, including oil casing, tubing, and ground oil pipelines. The main types and properties of CBF casing, tubing, and ground oil pipelines are introduced, and the application effects and advantages, that prove CBF pipes could be technically used in oil fields, are analyzed. Meanwhile, the applications and prospects for CBF pipe in China have been discussed from following aspects, such as raw materials, technology index, and demands, as well as technical difficulties.