Interphase effects on the bend strength and toughness of an oxide fibre/oxide matrix composite

Abstract The effect of alumina–20 wt.% ZrO 2 (PRD-166) fibre and SnO 2 coating properties on the bending strength and toughness of alumina fibre/SnO 2 /glass matrix composites have been investigated. The mean strength of as-received alumina–20 wt.% ZrO 2 fibres was 1380 MPa for a gage length of 17 mm and decreased with increase in heat treatment temperatures. It was also observed that as the SnO 2 coating thickness increased, roughness of the coating increased and this decreased the strength of the fibres. This roughness effect had serious implications on the fracture characteristics of PRD-166/SnO 2 /glass and Saphikon/SnO 2 /glass matrix composites. PRD-166/SnO 2 /glass matrix composites exhibited non-planar failure with fiber bridging and fibre debonding as major toughening mechanisms. Saphikon/SnO 2 /glass matrix composites failed in a tough manner with extensive fibre pullout. The difference in the failure mode between PRD-166/SnO 2 /glass and Saphikon/SnO 2 /glass matrix composites was attributed to the clamping stress associated with fiber roughness at the PRD-166/SnO 2 interface as compared to the smoother Saphikon/SnO 2 interface.