Flaw-Tolerant Ceramic Laminate Composites With Large Threshold Strengths
Tech ID: 10148 / UC Case 1999-385-0
The strength of brittle materials, including ceramics and glasses, must be described by statistical parameters because they contain an unknown variety of cracks and crack-like flaws inadvertently introduced during processing. Typical flaws found at fracture origins include large voids produced by organic inclusions (e.g. human hair) and inorganic inclusions (e.g. dust particles). The lack of plastic deformation in ceramics causes their strength to be inversely dependent on the size of very small cracks, which generally cannot be detected except by failure itself. For this reason, ceramic components frequently have a high probability of failure.
DESCRIPTIONScientists at the University of California have developed a new method for the production of flaw-tolerant ceramic laminate composites. These composites have a minimum strength, i.e. there is virtually zero probability of failure below a threshold value. These flaw-tolerant ceramics are produced by incorporating thin layers that are under large biaxial residual compression. Until the threshold value is reached, cracks are trapped between pairs of these thin compressive layers (due to a reduction of the stress intensity in the layers).
APPLICATIONSThis method has been tested with ceramics and is expected to be useful for other brittle materials, including glasses, many polymers, and some metals.
ADVANTAGESThis method makes possible the production of brittle materials with virtually zero probability of failure below a threshold strength. As a result, engineers will now be able to reliably design with such materials.
|United States Of America||Issued Patent||6,878,466||04/12/2005||1999-385|
- Lange, Frederick F.
- Rao, Masa P.
- Sanchez Herencia, Antonio Javier
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