Science of Fracture.

This research program is intended to explore and develop commonalities in fracture theory as applied to wide classes of differing materials at different scales- from the atomic to the continuum. Primary attention is focused upon analytical and experimental methods needed to analyze underlying and potentially common basic mechanisms controlling the fracture process, e.g. two and three-dimensional stress singularities, effect of environment, etc. and to examine structure-property relationships, including the effect of the fabrication process upon the preparation of specimens made from standardized model materials representative of polymers and metals. Major results during this year include additional analysis and development of a cracked Brazil specimen for deducing Mode II fracture toughness, further parametric analysis of the effect of geometry in an embedded fiber or rod and the location of initial interfacial debonding from the matrix upon resulting adhesive fracture under load, determination that initial phase of fracture in a cobalt-nickel alloy MP 35 is probably void nucleation caused by grain boundary sliding during dynamic recrystallization, plasma activated sintering can product apparently clean, active particle surfaces in silicon carbide powders, and that it is realistic to plan generating two standard reproducible materials - one epoxy resin and one linear viscoelastic polymar- which can be used to relate chemical structure to mechanical properties. Author