OPTIMAL-DESIGN OF SYMMETRICAL ANGLE-PLY LAMINATES SUBJECT TO NONUNIFORM BUCKLING LOADS AND INPLANE RESTRAINTS

Optimal buckling designs of symmetrically laminated rectangular plates under in-plane uniaxial loads which have a nonuniform distribution al ong the edges ave presented. In particular, point loads, partial unifo rm loads and nonuniform loads ave considered in addition to uniformly distributed inplane loads which provide the benchmark solutions. Poiss on's effect is taken into account when in-plane restraints are present along the unloaded edges. Restraints give rise to in-plane loads at u nloaded edges which lead to biaxial loading, and may cause premature i nstability. The laminate behaviour with respect to fiber orientation c hanges significantly in the presence of Poisson's effect as compared t o that of a laminate where this effect is neglected. This change in be haviour has significant implications for design optimisation as the op timal values of design variables with or without restraints differ sub stantially. In the present study, the design objective is the maximisa tion of the uniaxial buckling load by optimally determining the fiber orientations. The finite element method coupled with an optimisation r outine, is employed in analysing and optimising the laminates. Numeric al results ave given for a number of boundary conditions and for unifo rmly and non-uniformly distributed buckling loads. (C) 1996 Elsevier S cience Ltd.