Thermo-mechanical fatigue failure mechanisms and probabilistic fatigue life assessment of C/SiC composites based on GM-Bootstrap method

The durability of C/SiC composite structures is a crucial performance for reusable launch vehicles. In this work, the thermo-mechanical fatigue failure mechanisms of C/SiC composites subjected to cyclic load in hightemperature environments are investigated. The macro- and micro-scale fracture morphologies of composites are captured to elucidate the degradation mechanisms of fatigue life of C/SiC composites under different high temperatures. The experimental results illustrate that the prolonged and oxidizing high-temperature environment causing oxidation of fibers plays a dominant role in decreasing its fatigue performance. To break through the limitations of high costs on testing time and specimens, a novel fatigue life prediction methodology for C/SiC composites with small samples is proposed through integration of the grey model GM(1,1) with the bootstrap method, enabling probabilistic estimation of fatigue life distributions with limited experimental data. The probabilistic fatigue life (P-S-N) of C/SiC composites predicted by the developed model provides quantitative insights and engineering guidelines for the durability designs of hot structures in reusable launch vehicles.