Oxidation damages and a stiffness model for 2D-C/SiC composites

Two kinds of 2D-C/SiC specimens with different interface strengths were chosen to perform a non-stress oxidation experiment at 700℃ in air. The SEM analysis shows that the oxidation mechanism of the material surface is reaction-controlled kinetics and the fibers become thin uniformly；the oxidation inside the material is diffusion-controlled，and the oxidized fibers exhibit a local notch or “neck-shrink” phenomenon. The oxidation results in the decrease of the modulus and strength by reducing the effective load bearing area. The specimens with strong interface have higher modulus but lower strength，while those with weak interface behave reversely and the fiber pullout is much longer. Based on the SEM analysis results，a micromechanical model was formulated for the initial modulus calculation. The simulation results are in good agreement with the experimental values.