Numerical analysis of out-of-plane thermal conductivity of C/C composites by flexible oriented 3D weaving process consid
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Numerical analysis of out-of-plane thermal conductivity of C/C composites by flexible oriented 3D weaving process considering voids and fiber volume fractions Zheng Sun1,2 , Zhongde Shan1,a), Tianmin Shao2, Qun Zhang1 1 State Key Laboratory of Advanced Forming Technology and Equipment, China Academy of Machinery Science and Technology, Beijing 100044, China 2 Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China a) Address all correspondence to this author. e-mail: [email protected]
Received: 22 February 2020; accepted: 18 June 2020
Thermal conductivity behaviors are one of the most important evaluations of carbon fiber-reinforced carbon matrix (C/C) composites in the field of thermal protective structures. In order to deepen the understanding of the thermal conductivity behaviors of C/C composites, the out-of-plane thermal conductivity of C/C composites is studied by considering voids and the fiber volume fractions. The representative volume element (RVE) models of microscale and mesoscale are proposed. The parameters of the RVE models are captured by X-ray micro-computed tomography. The carbon matrix equivalent models and fiber volume fraction models along the z-direction were established. The effects of the porosity and fiber volume fraction along the z-direction on the thermal conductivity were analyzed. The proposed model was validated by experimental results at room temperature. Further, the numerical methods developed in this study can provide guidance for predicting the thermal conductivity of C/C composites with complex structures.
INTRODUCTION Carbon fiber-reinforced carbon matrix composites (C/C) have been extensively employed, e.g., in the aerospace and aircraft fields and automobile industry, owing to their excellent properties, such as their high specific strength and stiffness, hightemperature resistance, high mechanical strength at high temperatures, and outstanding corrosion resistance [1, 2, 3, 4, 5]. C/C composites experience severe mechanical and thermal conditions that can result in thermal stress concentration. The inconsistency in the thermal stress induced by uneven temperature distributions is one of the main reasons for component deformation and fatigue [6, 7, 8, 9]. Therefore, the accurate evaluation of the thermal conductivities of C/C composites is of great significance to clearly understand and design C/C composites. The thermal conductivity of C/C composites has been widely investigated experimentally in previous studies [9, 10]. However, most of these studies focused on polymer matrix composites, while few focused on C/C composites.
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Baxter et al. [10] concluded that the thermal conductivity of C/C composites manufactured by chemical vapor infiltration (CVI) with a low density increases between 1000 and 2000 °C. The effects of the microstructures of the carbon matrix on the thermal conductivities of the C/C composites were investigated. Luo et al. [9] measured the thermal conductivity of C/C composites ranging from 0 to
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