ABSTRACT
In order to characterize material behavior of complex systems, a knowledge of the elastic modulus is essential. For many systems the modulus has been shown to vary on a very fine scale such as in the interphase between the fiber and the matrix in traditional composites [1] and between the adherend and adhesive in a bonded joint [2]. In these regions, material properties change on the spatial scale of a
few tenths of a micrometer to a few micrometers. In order to determine and map modulus variations such as these, knowledge of the local stresses and strains is needed at an appropriate scale. For example, in adhesive joints, researchers often postulate the presence of an interfacial region with different mechanical properties from the bulk adhesive. A knowledge of the displacements near the interface that occur on loading an adhesive joint would supply direct evidence for modulus variations in this region.
