Dynamic Stability of Delaminated Cross ply Composite Plates and Shells

Abstract

Fibre reinforced composite plates and shells are increasingly replacing traditional metallic ones. The manufacturing process and service of the composite laminates frequently lead to delamination. Delamination reduces the stiffness and strength of composite laminates because they allow out of plane displacement of plies to occur more easily. Dynamic stability analysis is an integral part of most engineering structures. The present work deals with the study of the effects of free vibration, buckling and dynamic stability of delaminated cross ply composite plates and shells. A first order shear deformation theory based on finite element model is developed for studying the instability region of mid plane delaminated composite plate and shell. The basic understanding of the influence of the delamination on the natural frequencies, non- dimensional buckling load and non-dimensional excitation frequency of composite plates and shells is presented. In addition, other factors affecting the vibration, buckling and dynamic instability region of delaminated composite plates and shells are discussed. The numerical results for the free vibration, buckling and dynamic stability of laminated cross-ply plates and shells with delamination are presented. As expected, the natural frequencies and the critical buckling load of the plates and shells decrease with increase in delamination. Increase in delamination also causes dynamic instability regions to be shifted to lower excitation frequencies.