Potential of porous pyrolytic carbon for producing zero thermal expansion coefficient composites: A multi-scale numerical evaluation

This paper investigates the feasibility of using porous pyrolytic carbon (PyC) to produce low thermal expansion (CTE) carbon/carbon composites by using a multi-scale representative volume element (RVE) based on a finite element (FE) homogenisation strategy. The distribution of pores is characterized by mercury intrusion test and multi-peak Gaussian function. The RVEs of porous structures at micro- and macro-scale are generated using a modified random sequential adsorption (RSA) algorithm. The effective CTEs of porous PyC composites are obtained by implementing the periodic boundary conditions and the numerical implementation is detailed herein. The predicted effective macroscopic CTEs are validated by experimental measures. The results show that the absolute values of effective macroscopic CTEs of PyC composites nonlinearly increase with increasing pore volume fraction. For the high-texture (HT) chopped C/C composites, the effective CTEs reach a minimum at fibre yarn volume fraction of V_fm ≈ 7%, whereas the effective CTEs of low-texture (LT) PyC composites increase with increase of the fibre volume fraction. In addition, the effect of aspect ratio of the fibre yarn on the effective CTEs of both HT and LT composites are not significant.