SMOOTHING FINITE-ELEMENT AND EXPERIMENTAL HYBRID TECHNIQUE FOR STRESS ANALYZING COMPOSITES

A smooth two-dimensional numerical technique is presented for representing and differencing discrete moire data. The concept extends a previous approach to enable simultaneous processing of both in-plane measured displacements and thereby obtain smooth displacement functions and continuous strains full-field. A cluster of positive definite functionals is formulated and minimized to best approximate the experimental data. This variational problem is solved by a finite-element method. Arbitrarily shaped regions can be fitted with relatively few elements, neither boundary displacements nor their derivatives need to be specified, and experimental data locations may occur in any configuration. Little experimental input data are needed, and the inherent smoothing reduces the effects of experimental scatter. The technique is particularly effective for determining shear strains, and/or strains along a curved line such as the edge of a geometric discontinuity. The method is demonstrated by the moire strain analysis of a tensile composite plate containing a hole.