Transverse fracture toughness of unidirectional and hybrid ceramic matrix composites

Abstract

Reinforcing ceramic materials with unidirectionally aligned continuous fibers improves the mechanical properties in the fiber direction but often results in reduced transverse strength and toughness. As an effort to improve the transverse characteristics of unidirectiona l fiber reinforced ceramic matrix composites, randomly dispersed fine whiskers can be added to the matrix. The result is a hybrid ceramic matrix composite. Transversely oriented three-point chevron-notched-beam flexural testing was per-formed on monolithic cordierite, unidirectional continuous SiC fiber reinforced cordierite and a hybrid combination of continuous SiC fibers and SiC whiskers. The opening mode plane-strain fracture toughness analysis was based on methods presented in ASTM STP-855. The results indicate the transverse fracture toughness of fiber reinforced ceramic matrix composites can be significantly improved with the addition of whiskers to the matrix.