EFFECT OF PLY THICKNESS ON FRACTURE OF NOTCHED COMPOSITE LAMINATES

The effect of ply thickness on unnotched and notched strength of fiber -dominated laminates is investigated. Experiments are conducted to exa mine the effect of subcritical damage on fracture toughness of AS4/350 1-6 graphite/epoxy laminates with cross-ply and quasi-isotropic config urations. It is observed that ply thickness has a significant effect o n the notched behavior of cross-ply laminates but less so for quasi-is otropic laminates. The experimentally observed crack-tip damage in the form of axial splitting in the 0-deg plies and delamination is modele d by a two-dimensional finite element analysis using Mindlin plates, a nd the criterion that controls damage (split) growth is established. T he role of such damage on crack-tip stress distribution is investigate d, and inferences are drawn to determine the circumstances under which a fracture mechanics type of failure model can be used to predict the notched response of these laminates.