DELAMINATION AND DAMAGE STUDIES OF COMPOSITE-MATERIALS USING PHASE-SHIFTING INTERFEROMETRY

Composite materials offer a unique advantage over conventional enginee ring materials in that structural properties can be tailored to suit s pecific applications. However, the inherent anisotropy and the discret e layer-by-layer fabrication method of composite materials lend to mec hanical behavior and failure characteristics that are quite differ-ent from those of homogeneous materials. Consequently failure modes such as delamination in polymer matrix composites and matrix cracking and d amage in ceramic matrix materials prohibit these materials from being used in conventional engineering structures, as well as making their c haracterization in the laboratory difficult. In this paper, an experim ental photomechanics technique called phase-shifting moire interferome try is described. This technique is capable of providing analysts and designers (both material and structural) with detailed displacement an d strain fields near discontinuities in these materials. The technique allows high resolution measurements of in-plane surface displacements to be made without introducing global smoothing errors, thus preservi ng the integrity of data near cracks, discontinuities and material int erfaces. In this paper, the advantages of phase-shifting moire interfe rometry will be illustrated through several problems involving composi te materials.