Mechanical and microstructural characterisation of SiC- and SiBNC-fibre reinforced CMCs manufactured via PIP method before and after exposure to air

Non-oxide CMCs based on pyc-coated SiC-fibres (Tyranno SA3™) as well as novel amorphous ceramic fibres in the quaternary system Si–B–C–N (named SiBNC-fibres) were manufactured via polymer infiltration and pyrolysis process. Two different fibre architectures were applied: 0|90° unidirectional (UD) cross-ply and 0|90° plain weave fabric layer. UD cross-ply reinforced CMCs exhibit much more uniformly distributed filaments leading to better infiltration efficiency in resin transfer moulding process. Bending strength and fracture behaviour are strongly influenced by fibre architecture: UD cross-ply reinforced CMCs show higher bending strengths and less non-linear behaviour compared to plain weave fibre reinforcement. In tensile test there is no evidence of an influence of fibre architecture. Mechanical properties of unexposed SiCpyc/SiCN and SiBNCpyc/SiCN strongly correlate with fibre properties. After exposure to air (T = 1100 °C, 20 h), a significant decrease of mechanical properties could be observed, caused by complete oxidation of pyc-fibre coating interfered with silica formation.