EXPERIMENTAL-VERIFICATION OF SPLINE STRESS-ANALYSIS METHOD FOR A STRUCTURAL COMPOSITE LAMINATE CONTAINING A HOLE

Moire interferometry surface strain measurements for a uniaxially load ed composite laminate with an open hole were compared to predictions f rom three-dimensional spline variational theory, from two-dimensional finite element analysis, and from two-dimensional elasticity theory. S train measurements and a progressive damage investigation were accompl ished using twenty-eight ply fiber dominated, IM7/5250-4, laminates. A t low load levels, prior to matrix cracking, phase shifting moire inte rferometry was used to measure in-plane displacements. Experimental su rface strains were calculated based on digital analysis of the displac ement fields. Direct comparisons between theory and experiment were ma de using contour plots of epsilon(xx), epsilon(yy), and gamma(xy). For all in-plane surface strains, the spline variational theory results s howed good agreement with experiment in close proximity to the hole. A separate group of specimens were loaded incrementally until failure, and the initiation and progression of damage was documented using x-ra y images. Regions where the stress exceeded the ultimate transverse st rength are compared to the actual damage images using contour plotting schemes. Overall, the location of initial failure as predicted by the spline variational theory corresponded well with damage observations for early stages of damage.