LAYUP OPTIMIZATION AGAINST BUCKLING OF SHEAR PANELS

The object of the study was to optimize the shear buckling load of laminated composite plates. The laminates lacked coupling between bending and extension (B(ij) = 0) but had otherwise arbitrary selection of the ply angle variation through the thickness. The plates were rectangular and either simply supported or clamped on all edges. For orthotropic plates, it was seen that there is only one parameter necessary for finding the optimal design for different materials and plate aspect ratios. This parameter can be interpreted as the layup angle theta in a (+/- theta) orthotropic laminate. When bending-twisting coupling is present, the buckling strength depends on the direction of the applied load. A laminate with non-zero bending-twisting coupling stiffnesses can be described with four lamination parameters. The allowable region of these parameters was investigated, and an optimization of the buckling load within this region was performed. It was seen that even this is a one parameter problem. This parameter can be interpreted as the layup angle theta in an off-axis unidirectional laminate (theta).