Mesoscale damage analysis of needle-punched carbon/carbon composite considering randomness of inherent defects

Needle-punched carbon/carbon composites (NP C/Cs) are widely used in aerospace applications thanks to their good high-temperature mechanical properties with relatively low cost. To improve their out-plane stiffness and strength, short-cut fibres are introduced into interlayers between plies using a needle-punching technology. This could result in some defects that decrease their in-plane stiffness and strength. Circle-arc beam elements and extended spring elements are proposed in this research to model mechanical performances of punched fibre bundles, isotropic pyrocarbon matrix and short-cut carbon fibre felts in NP C/Cs, respectively. Aided by this beam-spring finite element model, the impacts from features of mesoscopic defects, e.g. irregularity of distribution of local imperfection in planar fiber bundle caused by punching process, to mechanical properties of NP C/Cs are focused in this study. The ranges of bending modulus and bending strength for a NP C/C are estimated considering the randomness of these defects.