AN ANALYTICAL STUDY ON 0/90-PLY-DROPS IN COMPOSITE LAMINATES

A simple model of two consecutive plies (either 0-degree or 90-degrees) being dropped on to a base laminate is formulated. The stresses near the ply-drops are analysed initially to determine the potential delamination sites. Further, strain energy release rates G(I) and G(II) are determined for a delamination existing at the potential delamination site. A geometrically non-linear FEM analysis code (SANGAM) is used for the purpose. Variation of G(I) and G(II) with delamination size, ply-drop distance, lay-up of the base laminate and orientation of dropped plies is investigated. Results of the analysis are discussed with a view to generating guidelines for design. Significant conclusions are reached concerning ply-drops between 0 and 90-degrees plies, bunching of plies of the same orientation and interaction of ply-drop distance, the allowable delamination size and the G(IC) of the material.