ABSTRACT-The three-dimensional finite element computer program has been developed to investigate interlaminar stresses in thick composite laminates. The finite element analysis is based on displacement formulation employing curved isoparametric 16-node elements. By using substructure technique, the program developed is capable of handling any composite laminates which consist of any number of orthotropic laminae and any orientations. In this paper, solid laminates and laminates with a circular hole were taken to study interlaminar stresses at the stright edge and the curved edge, respetively. Various solid laminates such as $[45_n/0_n/-45_n/90_n]_s$, $[45/0/-45/90]_ns$, and $[45/0/-45/90]_sn$ (n=1~4) were analyzed. And, $[45/0/-45/90]_sn$ laminates with a circular hole were stusied for n=1~20. The effect of laminate thickness, stacking sequence and circular hole on the interlaminar stresses near the free edge was investigated. Interlaminar stresses were governed by stacking sequence rather than laminate thickness. The boundary layer width of the interlaminar normal stress in solid laminats did not increase with laminate thickness but with the unmber of plies in symmetric repeating unit. In contrast with solid laminate, the boundary layer width in the laminates with a circular hole increased with laminate thickness.
