The Repeatedly Tested Tensile Strength of Some Ceramic Whiskers and Surface Flaws

This investigation was concerned with the tensile strength of α-Al2O3 whisker fragments and β-SiC whisker fragments which remained after tensile testing of these whiskers. Outer surfaces and fracture surfaces of whiskers were observed by SEM. And relations between flaws and strength were discussed. The results obtained are as follows:(1) The repeatedly tested tensile strength of α-Al2O3 whiskers and β-SiC whiskers were found to be 1.5∼4 times as high as the initial tensile strength of these whiskers.(2) The remarkable increase of the repeatedly tested strength suggests that the stress concentration at surface flaws may cause fracture nucleation.(3) Many types of surface flaws which may affects the strength of whisker were observed by SEM. Among these surface flaws, “step” was the highest in number.(4) When an ideal interface between whisker and matrix can be obtained, the strength of whisker in a composite may be higher than in the air, because the stress concentration at surface flaws of whisker may be decreased in the composite.