V. Tikare et Sr. Choi, COMBINED MODE-I AND MODE-II FRACTURE OF MONOLITHIC CERAMICS, Journal of the American Ceramic Society, 76(9), 1993, pp. 2265-2272
The mode I, mode II, and combined mode I-mode II fracture behaviors of
a coarse-grained silicon nitride, a fine-grained silicon nitride, and
an alumina were investigated. These ceramics were fractured from two
types of fracture initiating flaws: small surface flaws and large sing
le edge precracks. The small surface flaws were introduced by Knoop in
dentation in flexural samples at various angles to the tensile stress
direction and fractured in four-point bending. The samples with large
precracks were fractured in the asymmetric four-point-bend geometry. T
he mixed-mode fracture toughness values obtained from the two flaw con
figurations were in good agreement with each other. All three ceramics
displayed very similar mixed-mode fracture behavior, although their m
icrostructures were not similar. Comparison of experimental data to mi
xed-mode fracture theories revealed that the minimum strain energy den
sity theory best described the mixed-mode fracture behavior of all thr
ee ceramics.