Buckling of multiple delaminated beams

Delaminations weaken a laminated beam, which then fails prematurely under in-plane compression. An exact buckling analysis is performed for beams with double delaminations. Novel adoption of two coordinates and choice of slope as the unknown function reduce the buckling equations to simple solvable geometric equations. Complex buckling behaviors emerge for different sizes and depths of the delaminations. “Free mode” and “constrained mode” of buckling are identified. Both global and local buckling occurs, depending upon the slenderness ratios of the delaminations. In addition, an upper bound and a lower bound of buckling loads are obtained by assuming totally “constrained” and totally “free” deformation for the delaminated beam. These bounds are easy to compute and provide useful approximations. 0 1998 Elsevier Science Ltd