SiCウィスカー強化及びSiC粒子分散複合材料の疲労破壊機構

抄録

Fatigue property was examined for three commercially fabricated aluminum matrix composites containing SiC whiskers and particles under rotating bending in laboratory air. Fatigue strength at 10⁷ was about 67% higher for composite than that for matrix alloy, while for SiC_p/A356 and SiC_p/A357 composites the fatigue strengths of those composites were also higher than that for matrix alloy. Fractography revealed that mode II crack propagated through the whisker/matrix or particle/matrix interface for SiC_w/A2024 and SiC_p/A357 composite materials. On the other hand, for SiC_p/A356 composite material crack initiated at some small voids situated beneath the surface of the specimens. In the region of fatigue crack propagation the crack arrested to the whiskers or particles for small crack length (or lower stress level), while for longer crack length (or higher stress level) voids or sub crack around the whiskers or particles situated ahead of the main crack. Mode I and Mode II fatigue crack propagation models was proposed and those models could discuss the increase of fatigue strength of composite materials in comparison to matrix materials.