Hierarchically modeling the elastic properties of 2D needled carbon/carbon composites

In this study hierarchical micromechanical modeling is presented for prediction of the elastic properties of 2D needled carbon/carbon (C/C) composites. The modeling is based upon the analysis of the representative volume element (RVE) models of the hierarchical microstructure of composites. The prediction procedure consists of two sequential levels covering: (1) unidirectional fiber ply consisting of continuous fibers, matrix and randomly distributed pores and short-chopped fiber felt consisting of matrix and randomly distributed short fibers and pores; (2) needled laminate consisting of homogenous layers of fiber plies and felts and the needling yarn. Mori-Tanaka theory based method and strain energy-based finite element approach are used to calculate the effective properties of constituent materials and overall composites. Predictions are compared with experimentally measured data to verify the proposed model. In addition, a series of numerical predictions are performed to examine the influences of the thickness ratio of short-chopped fiber felt to unidirectional fiber ply and the needling periodicity on the elastic moduli of composites.