The mechanical behaviour of glass and glass–ceramic matrix composites

The mechanical behaviour of several glass and glass–ceramic composites was studied, with particular interest in axial and off-axis properties. The embrittlement of a cross-ply composite of carbon fibre reinforced borosilicate glass was attributed to the formation of a fibre/matrix interfacial reaction layer during processing. The tensile properties for cross-ply BMAS (BaO, MgO, A12O3, SiO2) glass-ceramic composites reinforced with silicon carbide fibres exhibited higher matrix cracking stresses in the 90 and 0° plies than the carbon fibre reinforced borosilicate glass composite. These were attributed to the presence of residual stresses that caused the glass–ceramic matrix in compression. Failure strengths in excess of 300 MPa were found for these glass–ceramic composites. Off-axis properties for cross-ply laminates were found to strongly depend on the volume fraction of fibres. Composites with lower fibre volume fractions exhibited higher interlaminar strengths than those with higher fibre volume fractions. There also appeared to be a link between inhomogeneous microstructures and a larger variation in mechanical properties.