Crack bifurcation in laminar ceramic composites

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1996.tb08003.x· OSTI ID:282210

Oechsner, M; Hillman, C; Lange, F F ^[1]

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1. Univ. of California, Santa Barbara, CA (United States). Material Dept.

Crack bifurcation was observed in laminar ceramic composites when cracks entered thin Al{sub 2}O{sub 3} layers sandwiched between thicker layers of Zr(12Ce)O{sub 2}. The Al{sub 2}O{sub 3} layers contained a biaxial, residual, compressive stress of {approx}2 GPa developed due to differential contraction upon cooling from the processing temperature. The Zr(12Ce)O{sub 2} layers were nearly free of residual, tensile stresses because they were much thicker than the Al{sub 2}O{sub 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{sub 2}O{sub 3} layer on the bifurcation phenomena. Bar specimens were fractured in four-point bending. When the propagating crack encountered the Al{sub 2}O{sub 3} layer, it bifurcated as it approached the Zr(12Ce)O{sub 2}/Al{sub 2}O{sub 3} interface. After the crack bifurcated, it continued to propagate close to the center line of the Al{sub 2}O{sub 3} layer. Fracture of the laminate continued after the primary crack reinitiated to propagate through the next Zr(12Ce)O{sub 2} layer, where it bifurcated again as it entered the next Al{sub 2}O{sub 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{sub 2}O{sub 3} layers, crack bifurcation was observed only when the layer thickness was greater than {approx}70 {micro}m.

• Sponsoring Organization: USDOE
• OSTI ID: 282210
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 7 Vol. 79; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
BENDING
CERIUM OXIDES
COMPOSITE MATERIALS
CRACK PROPAGATION
FRACTURE PROPERTIES
INTERFACES
LAYERS
POISSON RATIO
RESIDUAL STRESSES
STRAINS
THERMAL EXPANSION
YOUNG MODULUS
ZIRCONIUM OXIDES