CRACKING AND DAMAGE MECHANISMS IN CERAMIC-METAL MULTILAYERS

Investigations of cracking in multilayered ceramic/metal composites ar e presented. Two aspects are considered: crack renucleation across int act single metal layers and subsequent crack extension. Crack renuclea tion criteria are determined and compared with predictions. High-resol ution strain-mapping techniques are employed to determine the surface strain fields surrounding cracks. Good agreement is found between thes e experimental measurements and the predictions of a small-scale yield ing model. Subsequent crack progression occurs either by the extension of a dominant, nearly planar crack or by the formation of a zone of p eriodically spaced cracks. Both patterns are analyzed. The dominant cr acking behavior is found to depend on the volume fraction and yield st rength of the metal.