Effect of processing temperature on interfacial layer formation in SiC fiber-reinforced glass-ceramic composites

Abstract

The high fracture toughness and non-catastrophic fracture behavior of fiber-reinforced ceramic matrix composites are due to the weak interfacial shear strength between fiber and matrix, permitting fiber-matrix sliding during failure. In SiC fiber-reinforced glass or glass-ceramic composites, such low interfacial shear strength is obtained by the presence of a carbon-rich interfacial layer. This provides a path for crack propagation, fiber pull-out, and fiber delamination during fracture. Hence, these composites have demonstrated very high fracture toughness (critical stress intensity factor of ∼ 17 MPam1/2) and high fracture strength (3 to 4 times larger than that of monolithic glass or glass-ceramics). The carbon-rich interfacial layer in these glass or glass-ceramic composites is formed by oxidation of the SiC fiber by the oxide matrix during hot pressing. Its thickness is governed by hot pressing time, temperature, and pressure. In our results on Nicalon SiC fiber-reinforced lithium aluminosilicate glass-ceramic composites, hot pressing temperature governed not only the thickness of the interfacial layer, but also the phases residing within it. In this paper, the effect of hot pressing temperature on the phases formed in the interfacial area is described.