Effects of Non-Uniform Needled Microstructure on Failure Mechanisms of 3d Needled C/C-Zrc-Sic Composites Thick-Walled Cylinder Under Axial Compression and Internal Pressure

Abstract

Three dimensional (3D) needled ZrC-SiC modified C/C composites (C/C-ZrC-SiC composites) as cutting-edge materials for throat or expansion section of rocket nozzle are mainly subjected to complex loads conditions of internal pressure and axial force. The coupled axial compression and internal pressure experiments of 3D needled C/C-ZrC-SiC composites thick-walled cylinder were carried out to study the damage modes and failure mechanisms combing with the optical microscope and micro computed tomography (Micro-CT). A meso-macro finite element (FE) model considering local needling fiber regions was also established to investigate the failure process of the thick-walled cylinder under the complex loads. The predicted strength, failure strain and ultimate crack morphologies obtained by the proposed model were in good agreement with the experimental results. The effect of needled region distribution on the crack evolution and damage mechanisms was further analyzed. The non-uniform distribution of needled fiber region can induce the stress concentration of no needled regions under circumferential tension, which can trigger crack initiation and deflection. This study can be helpful of establishing the relationship between the structural behavior of ultra-high temperature ceramics modified C/C composites nozzle and the 3D needled composites design.

Keywords: composites, Mechanical properties, Finite element analysis, Failure mechanisms