Predicting the effective properties of 3D needled carbon/carbon composites by a hierarchical scheme with a fiber-based representative unit cell

This paper presents a fiber-based representative unit cell (fRUC) on the mesoscale to estimate the elastic constants of a three-dimensional (3D) needled carbon/carbon (C/C) composite through a hierarchical modeling scheme. The material variations due to needle-punching, including fiber dislocations, fiber distributions and matrix pockets, are precisely considered in the proposed fRUC model. A quarter-size mathematical model with a periodic boundary condition of a general mesh is established to perform the fRUC analysis by using interpolation functions. The predictive results from the fRUC are transitioned to a ply representative unit cell (pRUC) based on the developed analytical homogenization method. The proposed model agrees well with the experimental results, and the effects of microstructural parameters on the overall composite properties are discussed. The results allow great confidence in the reliable predictions of the effective properties and the damage and strength of 3D needled C/C composites.