A SIMPLE BEAM THEORY FOR THE BUCKLING OF SYMMETRICAL COMPOSITE BEAMS INCLUDING INTERACTION OF INPLANE STRESSES

A theory for symmetrically laminated, doubly-symmetric composite beams including the effects of anticlastic curvature is presented. Verifica tion of the theory is demonstrated through comparisons with classical plate theory on the buckling loads for eight-layer symmetric angle-ply laminates caused by uniform compression and linearly distributed stre ss (lateral-torsional buckling). A significant reduction in buckling l oad is observed when the beams have many layers that are oriented betw een 25 and 60 degrees. Closed-form approximations for the new theory f or rectangular beams are also presented and the theory is applied to b ox and I beams. These results show a reduction in the buckling load as compared to other beam theories for the box beams and for strong axis buckling of the I beams when there are many layers with lamination an gles between 25 and 60 degrees. (C) 1998 Elsevier Science Ltd. All rig hts reserved