Damage tolerance evaluation of a C/C-SiC composite body flap of a re-entry vehicle

This paper deals with the delamination propagation in Ceramic Matrix Composites (CMC) for spacecraft applications. Presently, Ceramic Matrix Composites (CMC) are increasingly adopted for application where heat resistance and structural stiffness requirements need to be fulfilled at the same time. In particular, in aerospace applications, where the lightweight requirement is of primary concern, CMC materials seem to be the most fascinating solution for effective and performant design. One of the possible limits in the use of such materials for aerospace applications is related to the onset and evolution of damages, in particular by delamination under service loading conditions. Indeed, commonly used rules and regulations on delamination propagation, which are well-established for carbon fibre reinforced plastic, are not straight applicable for CMC materials due to the specific nature of this ceramic materials. Moreover, methodologies for fracture toughness evaluation are still in a preliminary stage for these materials. In this work, a preliminary CMC material model calibration for Cohesive elements numerically has been performed at coupon level (DCB and ENF tests) and validated by experimental literature data. Secondly, a sensitivity analysis on delamination position and size has been carried out on a C/C-SiC body flap for a reusable reentry vehicle. To comply with a step by step gradually increased model complexity-based damage tolerance approach, preliminary analyses have been performed on plates with embedded circular delamination, comparing the delamination onset stress level with respect to the stress state corresponding to the most critical body flap service load.