RECENT DEVELOPMENTS IN VELOCITY AND STRESS MEASUREMENTS APPLIED TO THE DYNAMIC CHARACTERIZATION OF BRITTLE MATERIALS

The synthesis of novel brittle materials with tailored microstructures requires the understanding of new physical phenomena related to the f ailure of these materials. Observation capabilities with spatial resol ution of atomic dimensions, e.g., scanning tunneling microscopy (STM) and high resolution electron microscopy (HREM), have opened new fronti ers in the mechanical characterization of these advanced materials. Th e challenge is to design experiments capable of loading the material i n a controlled fashion such that defects, resulting in well defined ma croscopic stress and velocity features, are produced. In this article, techniques for the measurement of surface and in-material particle ve locities and in-material axial and transverse stress measurements are reviewed. Examples on the usefulness of these techniques in the study of brittle failure are provided. A variable sensitivity displacement i nterferometer is used in the measurement of normal and in-plane motion in pressure-shear recovery experiments conducted on fiber composite m aterials. In-material stress measurements with piezoresistance gauges are used in the identification of so-called failure waves in glasses. (C) 1998 Elsevier Science Ltd. All rights reserved.