HYGROTHERMAL EFFECTS ON THE BUCKLING OF LAMINATED COMPOSITE PLATES

The effects of moisture and temperature on the static instability of laminated composite plates are investigated. The analysis is carried out by the finite element method using a quadratic isoparametric element which takes transverse shear deformation into account. The conventional finite element formulation is modified to include hygrothermal effects. The stiffness matrix, geometric stiffness matrix due to residual stresses, geometric stiffness matrix due to applied in-plane loads and load vector of the element are derived based upon the principle of minimum potential energy. The analysis accounts for reduced lamina material properties at elevated moisture concentrations and temperatures. Critical loads are obtained for symmetric and anti-symmetric laminates with simply-supported and clamped boundary conditions at different moisture concentrations and temperatures. Their dependence on moisture and temperature is studied. The effects of aspect ratio and side-to-thickness ratio on the critical loads are also considered. Mode shapes are verified in a few cases for anti-symmetric cross-ply laminate.