Application of holography to anisotropic composite plates

The application of holography to stress analysis of opaque, anisotropic composite plates subjected to static or dynamic transverse and in-plane loads is presented. The equations of motion show that, for flexed, anisotropic, laminated composite plates, the complete state of stress at a generic point in any lamina, plus the moments and shear forces, are related to the temporal and spatial partial derivatives of the transverse displacement of the middle surface. Interferometric holography is shown to be well suited for obtaining the transverse displacement. Methods of determining the required spatial and temporal partial derivatives are discussed, an example being demonstrated. The holographic determination of anisotropic-material properties, stress and strain concentrations and the nondestructive evaluation of critical buckling loads for composite structures, plus the use of holographically obtained isopachics to supplement photoelastic analyses of composites, are also discussed. Experimental results for statically and dynamically loaded composite plates and beams with and without geometric discontinuities are presented to illustrate the concepts and techniques.