TY - JOUR
T1 - Competing fracture modes in brittle materials subject to concetrated cyclic loading in liquid environments
T2 - Trilayer structures
AU - Hermann, Ilja
AU - Bhowmick, Sanjit
AU - Zhang, Yu
AU - Lawn, Brian R.
N1 - Funding Information:
This work was supported by a grant from the National Institute of Dental and Craniofacial Research (PO1 DE10976). Discussions with Herzl Chai (University of Tel Aviv) and assistance with Oriented Finite Element Analysis (OOF) calculations (Appendix) by Stephen Langer (National Institute of Standards and Techology) are gratefully acknowledged.
PY - 2006/2
Y1 - 2006/2
N2 - A study is made of top-surface cracks induced in brittle trilayers by cyclic indentation with a hard sphere in water. The trilayers consist of an external brittle layer (veneer) fused to an inner stiff and hard ceramic support layer (core), in turn adhesively bonded to a thick compliant base (substrate). These structures are meant to simulate essential aspects of dental crowns, but their applicability extends to a range of engineering coating systems. The study follows on from like studies of brittle monoliths and brittle-plate/soft-substrate bilayers. Competing fracture modes in the outer brittle layer remain the same as before: outer and inner cone cracks and radial cracks, all of which form in the near-contact zone and propagate downward toward the veneer/core interface. Inner cone cracks and radial cracks are especially dangerous because of their relatively steep descent through the outer layer as well as enhanced susceptibility to mechanical fatigue. Experiments are conducted on model glass/alumina/polycarbonate systems, using video cameras to record the fracture evolution in the transparent glass layer in situ during testing. Each fracture mode can lead to failure, depending on the maximum contact load and other variables (plate thickness, sphere radius). The potentially beneficial role of a stiff intervening core is discussed, along with potentially deleterious side effects of residual thermal-expansion-mismatch stresses.
AB - A study is made of top-surface cracks induced in brittle trilayers by cyclic indentation with a hard sphere in water. The trilayers consist of an external brittle layer (veneer) fused to an inner stiff and hard ceramic support layer (core), in turn adhesively bonded to a thick compliant base (substrate). These structures are meant to simulate essential aspects of dental crowns, but their applicability extends to a range of engineering coating systems. The study follows on from like studies of brittle monoliths and brittle-plate/soft-substrate bilayers. Competing fracture modes in the outer brittle layer remain the same as before: outer and inner cone cracks and radial cracks, all of which form in the near-contact zone and propagate downward toward the veneer/core interface. Inner cone cracks and radial cracks are especially dangerous because of their relatively steep descent through the outer layer as well as enhanced susceptibility to mechanical fatigue. Experiments are conducted on model glass/alumina/polycarbonate systems, using video cameras to record the fracture evolution in the transparent glass layer in situ during testing. Each fracture mode can lead to failure, depending on the maximum contact load and other variables (plate thickness, sphere radius). The potentially beneficial role of a stiff intervening core is discussed, along with potentially deleterious side effects of residual thermal-expansion-mismatch stresses.
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U2 - 10.1557/jmr.2006.0056
DO - 10.1557/jmr.2006.0056
M3 - Article
AN - SCOPUS:33644505154
SN - 0884-2914
VL - 21
SP - 512
EP - 521
JO - Journal of Materials Research
JF - Journal of Materials Research
IS - 2
ER -