Abstract: Based on the twodimensional elasticity theory, the buckling modes of delaminated composite beams were studied. Firstly, according to the plane elasticity theory, the analytical solution of a piece of homogeneous beam is obtained, which exactly satisfies the simply-supported conditions of the beam at two ends. Then, using the point collocation technique, taking the series terms equal to the matching points, the critical buckling loads were obtained by means of the interface equations at every points as well as the upper and lower surface conditions of the beam. The displacement modes of the beam are given by substituting the critical loads back to the eigenvalue equations. The possible contact on the delaminated interfaces is considered in the present study. “Free” and “contact” modes are separately computed. According to the situations of the vertical displacements and normal stresses on the delaminated interfaces, the real buckling modes can be judged. The effects of the sizes and positions of the delaminations on the buckling modes were investigated. The present method is applicable not only to the slender beams, but also to the thick beams. And the contact problem was also well solved.

Key words: laminated beam, delamination, buckling mode, point collocation, interface contact