Two-Scale Prediction of Effective Thermal Conductivity of 3D Braided C/C Composites Considering Void Defects by Asymptot
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Two-Scale Prediction of Effective Thermal Conductivity of 3D Braided C/C Composites Considering Void Defects by Asymptotic Homogenization Method Kun-long Wei 1
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& Jiang Li & Hong-bin Shi & Min Tang
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Received: 25 May 2019 / Accepted: 29 August 2019/ # Springer Nature B.V. 2019
Abstract In order to predict the effective thermal conductivities of three-dimensional (3D) braided carbon/carbon (C/C) composites with randomly distributed void defects. Two-scale prediction model is developed based on the asymptotic homogenization method. Unit cell models both on fiber-scale and fiber bundle-scale are established according to the scanning electron microscopy observation of the material, and the randomly distributed void defects are considered. The effective thermal conductivities of fiber bundles with void defects are predicted firstly, then the effective thermal conductivities of the 3D braided C/C composites are predicted considering void defects in matrix pocket and interface by introducing the predicted thermal conductivities of fiber bundles. The predicted effective thermal conductivities agree well with the experimental results, demonstrating the validity of the two-scale prediction model. A parametric study is then conducted to analyze the effects of void volume fraction and interfacial thermal conductivity on the predictions of the developed model. The results show that the random distribution of void defects has a little effect on the effective thermal conductivities, while the void volume fraction has a significant effect on the effective thermal conductivities. The thermal conductivities decrease generally linearly with the increase of void volume fractions, and the effect of void volume fraction of matrix pocket is greater than that of fiber reinforcement. The effective thermal conductivities increase with the increase of interfacial thermal conductivity, and the effect of void volume fraction of interface becomes larger with the increase of interfacial thermal conductivity. A higher interfacial thermal conductivity have a greater effect on the effective thermal conductivities of the material than a smaller interfacial thermal conductivity. Keywords 3D braided C/C composites . Effective thermal conductivity . Void defects . Two-scale modeling . Asymptotic homogenization method . Interfacial thermal conductivity
* Kun-long Wei [email protected] Extended author information available on the last page of the article
Applied Composite Materials
1 Introduction The 3D braided C/C composites is prepared by using 3D braided carbon fiber perform as reinforcement. They are lightweight, high delamination resistance and good thermal mechanical performance at high temperature, and often used for rocket motor nozzle, high-speed aircraft head, and space vehicle nose-cap [1–3]. As a material for thermal structure, the 3D braided C/C composite is usually subjected to high-temperature over 2300 K in a short period of time, in order to prevent the structure from failure due to excessive temperature, the thermal protecti
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