THE EFFECT OF SQUARE CUTOUTS ON THE NATURAL FREQUENCIES AND MODE SHAPES OF GRP CROSS-PLY LAMINATES

In this work, effects of square cut-outs on the natural frequencies and mode shapes of cross-ply laminates made of S-glass/epoxy, unidirectional pre-preg tape (Fiberite, Hy-E 9134B) are reported. The first three natural frequencies and mode shapes of cantilever plates (with or without cut-out defects) are investigated both experimentally and numerically. Holographic interferometry and piezo-electric sensing techniques are applied in the tests to record vibration mode shapes and natural frequencies, respectively. A finite element code based on the shear deformation theory of plates is developed to analyze the problem numerically. The test findings and calculated results for the first three natural frequencies agree well. The computed mode shapes and laser holograms resemble each other closely for all cases studied. Effects of the size of cut-outs, the location of defects, and the number of layers removed on the vibration frequencies are reported.