Flexural performance of laminated composite plates with diagonally perturbed localized delamination

Abstract

This paper investigates flexural performance of laminated composite plates in the presence of imperfect bonding in terms of localized delamination, commonly observed in manufacturing process, using finite element method incorporating virtually zero thickness interface element. The structural response in terms of maximum deflection of two-layer, built-in, and square composite laminates under the influence of transverse load is considered. For the discretization, each finite element is formulated such that it is consisting of three sub-elements representing the top and bottom composite laminae as well as the interface in between. Perturbation of localized interface rigidity is carried out diagonally with imperfection ratio, R, for numerous fiber orientations and damage intensities indicated by delamination area. In addition, location effect is examined by placing these damages at various sites characterized by the distance ratio measured from the laminated composite plate's center. A polar plot describing relative rigidity change for various damage intensities and locations as well as fiber angles has been produced to generalize the findings. Normalized rigidity is, in general, demonstrated to have a direct correlation with distance ratio for plates with high damage intensities. For similar degree of damage intensity, increase in orientation mismatch of top and bottom layers reduces the rigidity ratio, relative to that of matching fiber angles, corresponding to an increase in distance ratio. Flexural behavior of laminates with small delamination area is insensitive to position of imperfection although a drop in rigidity is shown in comparison to that with perfect bonding.