Premium
Crack‐Growth Resistance of in Situ ‐Toughened Silicon Nitride
Author(s) -
Choi Sung R.,
Salem Jonathan A.
Publication year - 1994
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.1151-2916.1994.tb07265.x
Subject(s) - fracture toughness , materials science , indentation , composite material , silicon nitride , toughness , fracture (geology) , fracture mechanics , layer (electronics)
The fracture toughness of a commercial, hot‐pressed, in situ ‐toughened silicon nitride with an elongated grain structure is determined by four different testing methods. The fracture toughness is found to be 5.76 ± 0.27, 8.48 ± 0.50, 10.16 ± 0.66, and 10.68 ± 0.39 Mpa.m 1/2 , respectively, by indentation crack size measurement, indentation strength, single‐edge‐precracked‐beam, and chevron‐notched‐beam methods. The discrepancy in fracture toughness between the testing methods is related to R ‐curve behavior, as measured using the indentation strength technique. These results indicate that there is no unique fracture toughness value and that a fracture toughness testing method with appropriate qualifiers is needed for rising R ‐curve materials. Therefore, care should be taken in interpreting and utilizing fracture toughness values evaluated from different testing methods if a material exhibits a rising R ‐curve. Complete characterization of the R ‐curve may be a prerequisite.