Thermal aging behavior of an SiC-fiber reinforced glass matrix composite in a non-oxidizing atmosphere

Abstract

The thermal aging in argon of a commercially available SiC-fiber reinforced glass matrix composite was investigated at temperatures in the range 500–700 °C for exposure duration of up to 1000 h. An inert atmosphere was used to study the effects of temperature alone, thus minimizing and neglecting the effects of oxidation. The mechanical properties of aged samples were evaluated at room-temperature by using four-point flexure strength and three-point flexure chevron-notch techniques. The interfacial properties were determined by push-out indentation measurements using an in-situ SEM indentation apparatus. The fracture toughness values determined by the chevron-notch tests were little affected by the aging conditions and were in the range 19–26 MPa√m . The frictional interfacial shear stress was not affected by the aging conditions either. For the most severe aging conditions investigated (1000 h at 600 °C and 100 h at 700 °C), a significant loss of flexure strength and stiffness of the samples was detected, which has been ascribed to microstructural changes that occurred in the material during aging as a consequence of the softening of the glass matrix. At these aging conditions, a lower interfacial shear stress for fiber-matrix debonding initiation was measured, which may be explained also by the occurrence of matrix softening and void formation.