NONLINEAR POST-BUCKLING ANALYSIS OF UNIDIRECTIONAL LAMINATED BEAMS WITH DELAMINATION

The unidirectional composite beam with buried delamination is divided into four sub-regions. Using the theory for composite laminates, the nonlinear relationship between the contact force and the deflections of the sub-regionsis established. The governing equations are derived by introducing the available contact effect into the geometric nonlinear theory of extensible beams. The four sub-regions are integrated into a whole beam by employing the continuity conditions at the delamination fronts. Assuming simply supported boundary conditions, the governing equations are solved through the perturbation approach. The analytical solutions of the buckling load and the post-buckling equilibrium path for the delaminated unidirectional composite beam are obtained by examining the composition of the differential equation of the beam and by analyzing the characteristics of its general and particular solutions. The effects of delamination length and depth on the critical buckling load and contact performance of the delaminated beam are discussed by numerical analysis. The theoretical solutions are compared with the results obtained from ABAQUS finite element analysis. The results show that the two solutions are in good agreement with each other. It is found that the buckling modes of the delaminated beam includes macroscopic failure modes and micro-buckling modes at the interfaces. Both the buckling load and contact performance are inherent properties of the delaminated beam. The former is affected by the geometric parameters and material properties of the beam, while the latter is mainly affected by the depth and length of the delamination.