Abstract
The effects of mechanical properties of a matrix on the tensile strength and fracture toughness of brittle fiber-reinforced metal matrix cpmposites have been investigated. Unidirectionally aligned continuous SiC fiber-reinforced composites with commercially pure aluminum matrix (SiC/CPA1) and aluminum alloy matrix (SiC/A384), both unnotched and notched specimens, were tensile-tested. Their failure behavior and the relation between tensile strength and nonlinear energy fracture toughness of the composites were examined.
The tensile strength and fracture toughness of SiC/CPA1 composite increased with increasing fiber volume fraction, while those of SiC/A384 composite decreased. There was a strong correlation between tensile strength and fracture toughness in the composites; the tensile strength increased proportionally with increasing fracture toughness. SiC fibers extracted from both composites were equal in atrength and scatter, and the interfacial strengths of the composites were interpreted to be sufficiently high for preventing stress relaxation by interfacial debonding. Such a difference of the fracture behavior would be due to the difference of the stress ralaxation mechanism following the initial fracture of weak fibers in the matrix metals. The present results meet the well-known concept that ductile and notch insensitive metal for the matrix is recommended to obtain a high strength composite using full potential of a brittle fiber.
