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Fracture Toughness Anisotropy and Toughening Mechanisms of a Hot‐pressed Alumina Reinforced with Silicon Carbide Whiskers
Author(s) -
Hansson Thomas,
Warren Richard,
Wasén Jonas
Publication year - 1993
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1993.tb05304.x
Subject(s) - materials science , whisker , fracture toughness , composite material , whiskers , silicon carbide , fracture mechanics , composite number , deflection (physics) , transgranular fracture , intergranular fracture , microstructure , intergranular corrosion , physics , optics
The fracture toughness of a hot‐pressed alumina and that of a hot‐pressed alumina/SiC‐whisker composite containing 33 vol% SiC whiskers were measured by four‐point bending on single‐edge precracked bend bars having sharp precracks created by “bridge indentation.” Two batches of the composite were examined, one exhibiting a greater degree of whisker clustering than the other. The fracture toughness of the alumina was around 4 MN·m ‐3/2 whereas that of the composite varied between 5 and 8 MN·m ‐3/2 depending on microstructural uniformity and crack‐propagation direction. Crack deflection in combination with a change in fracture from intergranular to transgranular fracture is proposed as an explanation of the superior fracture toughness of SiC‐whisker‐reinforced alumina as compared to unreinforced alumina. The composite exhibited a variation in fracture toughness with the crack‐propagation direction in identical crack planes. This effect could with good accuracy be described in terms of crack deflection for the composite with uniform whisker distribution. However, in the material with whisker clustering the variation of the fracture toughness with crack‐growth direction was greater and could not entirely be explained by crack deflection.