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Crack Bifurcation in Laminar Ceramic Composites
Author(s) -
Oechsner Matthias,
Hillman Craig,
Lange Fred F.
Publication year - 1996
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.1151-2916.1996.tb08003.x
Subject(s) - materials science , composite material , residual stress , ceramic , ultimate tensile strength , laminar flow , bifurcation , layer (electronics) , bending , physics , nonlinear system , quantum mechanics , thermodynamics
Crack bifurcation was observed in laminar ceramic composites when cracks entered thin Al 2 O 3 layers sandwiched between thicker layers of Zr(12Ce)O 2 . The Al 2 O 3 layers contained a biaxial, residual, compressive stress of ∼2 GPa developed due to differential contraction upon cooling from the processing temperature. The Zr(12Ce)O 2 layers were nearly free of residual, tensile stresses because they were much thicker than the Al 2 O 3 layers. The ceramic composites were fabricated by a green tape and codensification method. Different specimens were fabricated to examine the effect of the thickness of the Al 2 O 3 layer on the bifurcation phenomena. Bar specimens were fractured in four‐point bending. When the propagating crack encountered the Al 2 O 3 layer, it bifurcated as it approached the Zr(12Ce)O 2 / Al 2 O 3 interface. After the crack bifurcated, it continued to propagate close to the center line of the Al 2 O 3 layer. Fracture of the laminate continued after the primary crack reinitiated to propagate through the next Zr(12Ce)O 2 layer, where it bifurcated again as it entered the next Al 2 O 3 layer. If the loading was stopped during bifurcation, the specimen could be unloaded prior to complete fracture. Although the residual stresses were nearly identical in all Al 2 O 3 layers, crack bifurcation was observed only when the layer thickness was greater than ∼70 μm.