Generalized Quasi-Three Dimensional Finite Element Analysis of Laminates

Abstract

Quasi-three dimensional finite element method (Q3-DFEM) has been widely recognized as an effective method in analyzing symmetric laminates loaded in the longitudinal direction. However, when laminates are not symmetric or when bending moment is applied, Q3 DFEM is not sufficient to analyze composite laminates. A generalized Q3 DFEM (GQ3 DFEM) accounting for bending and twisting of unsymmetric laminates has been developed. In this paper, GQ3 DFEM based on the Kirchhoff hypothesis for laminates is formulated based on deformations separated into two parts, which are the global displacements corresponding to CLT, and the local displacements representing local states. As the local displacements can be separated from the global displacements based on CLT, the effect of local geometrical irregularities is directly evaluated. GQ3 DFEM is used to determine displacements, stresses and energy release rates. Finally it is shown that GQ3 DFEM based on the Kirchhoff hypothesis is useful for predicting the behavior of composite laminates.