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Relation between Strength, Microstructure, and Grain‐Bridging Characteristics in In Situ Reinforced Silicon Nitride
Author(s) -
Li ChienWei,
Lui SiuChing,
Goldacker Jeffrey
Publication year - 1995
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.1151-2916.1995.tb08823.x
Subject(s) - bridging (networking) , materials science , microstructure , grain size , fracture toughness , composite material , silicon nitride , drop (telecommunication) , computer network , telecommunications , computer science , layer (electronics)
The grain size of in situ Si 3 N 4 is varied, and its effects on strength‐flaw size relations are related to the behavior of a bridging zone behind the crack tip. The bridging‐zone properties are calculated from a Dugdale model assuming that the bridging zone has a constant bridging stress ( p *) and length ( D b ) at the moment of the critical fracture. The results show that as grain size increases, p * decreases while D b and the critical bridging zone opening ( u *) first increase and then decrease, resulting in a maximum for short‐crack fracture toughness at an intermediate grain size. The initial increase of u * and D b with grain size is attributed to an increase in debonding length, while the decrease of p * is attributed to a decrease in strength for bridging grains due to a statistical effect which also causes D b and u * to drop in the large‐grain regime. Implications on microstructure design are discussed.