Buckling analysis of delaminated composite beams

The effects of stacking sequences, fiber orientation angles, boundary conditions and delamination numbers on the critical buckling loads of the laminated composite beams have been investigated analytically and numerically. Firstly, an analytical model is presented to take into consideration the reduction in stiffness of the beam due to the presence of the delamination in the beam. Then, two-dimensional finite element models for the composite beams having single/double middle delaminations have been established by using contact element at ANSYS commercial program. A good agreement between theoretical and finite element results has been found. It is seen that the buckling loads vary with changing stacking sequences, orientation angles and boundary conditions. The results show that a reduction in the critical buckling loads occurs when delamination length increases. In the numerical analysis, the appropriate buckling load values of the laminated beams are obtained by using normal penalty stiffness that is chosen as elasticity modulus for contact elements in the delamination region.