Laminar Ceramics That Exhibit a Threshold Strength
M. P. Rao,
1
A.
J. Sánchez-Herencia,
1*
G. E. Beltz,
2
R. M. McMeeking,
12
F. F. Lange
1
Thin compressive layers within a laminar ceramic arrest large
cracks (surface and internal) and produce a threshold strength. This
phenomenon increases the damage tolerance of ceramics and will allow
engineers to design reliable ceramic components for structural
applications. The stress intensity factor derived for a crack
sandwiched between two compressive layers suggests that the threshold
strength is proportional to the residual compressive stress and the
thickness of the compressive layer and is inversely proportional to the
distance between the compressive layers. Laminates composed of thick
alumina layers (605 ± 11 micrometers) and thin mullite/alumina
compressive layers (37 ± 1.4 micrometers) fabricated for this
study had a threshold strength of 482 ± 20 megapascals, in fair
agreement with the theory.
1 Materials Department,
2 Department of Mechanical and Environmental
Engineering, University of California at Santa Barbara, Santa Barbara,
CA 93106, USA.
*
Present address: Instituto de Cerámica y Vidrio
(CSIC), Arganda del Rey, 28500 Madrid, Spain.
To whom correspondence should be addressed.
