BUCKLING ANALYSIS OF LAMINATED COMPOSITE BEAMS WITH MULTIPLE DELAMINATIONS

摘要

Buckling analysis of laminated composite beams with multiple delaminations based on a layer-wise finite element model is presented. The approach used accounts for transverse opening displacements as well as in-plane slippage of adjacent layers in delamination regions. However, the mathematical response of a delaminated structure sometimes includes physically inadmissible mode shapes. The lowest eigenvalue corresponding to a physically admissible mode is computed in the present study by reformulating the eigenvalue problem as a constrained minimization of the Rayleigh's quotient. Results are presented for the case where loading is applied uniformly in each layer to show the significance of the no-penetration condition. The buckled shapes are shown to be complex modes which are a strong function of the laminate stacking sequence and includes the interaction of several laminae. Buckling response of various delaminated and undelaminated stacking sequences is discussed next for the more common load application of constant strain. Load reduction due to delamination buckling and mode shape as a function of delamination length are discussed relative to laminate stacking sequence.