Microstructural and Mechanical Characterization of Damage Tolerant SiC/SiCN Ceramic Matrix Composites Manufactured via PIP Process

Abstract

Silicon carbide fiber reinforced SiC composites offer performance advantages such as higher temperature capability and significant lower density over the currently used metallic superalloys. In this work silicon carbide fiber reinforced nitrogenous SiC composites (SiC/SiCN) were manufactured by polymer infiltration and pyrolysis. As precursor a polyvinylsilazane with low viscosity was infiltrated via resin transfer molding into Tyranno SA3 fiber preforms, cured and pyrolyzed. Due to process induced shrinkage several reinfiltration and pyrolysis steps had to be performed until an acceptable porosity below 5% was achieved. The matrix precursor was investigated in terms of thermal behavior via differential scanning calorimetry and rheology measurement to find the ideal temperatures for the polymer infiltration step. Pure matrix specimens were cured and pyrolyzed. The densification during pyrolysis was investigated in terms of thermogravimetric analysis, He gas pycnometry and X-ray diffraction. Finally the microstructure of the composite and the quality of the infiltration process was characterized by SEM and CT. To determine the mechanical properties of the SiC/SiCN composites, samples were tested by means of 3-point bending.