Hygrothermal effects on the dynamic behavior of multiple delaminated composite plates and shells

A quadratic isoparametric finite element formulation based on the first ord er shear deformation theory is presented for the free vibration and transie nt response analysis of multiple delaminated doubly curved composite shells subjected to a hygrothermal environment. A simple multiple delamination mo del developed by the authors earlier is employed to take care of any number /size of delamination located anywhere in the laminate. The analysis takes into account the lamina material properties at elevated moisture concentrat ion and temperature. Newmark's direct integration scheme is used to solve t he dynamic equation of equilibrium at every timestep during the transient a nalysis. Several numerical examples are considered and the results are comp ared with those available in the literature. The results show a reduction i n the fundamental frequency with an increase in the percentage of uniform m oisture content as well as temperature for simply supported antisymmetric c rossply and angleply laminates for any size of delamination considered. The central dynamic displacements and the stresses at the center of laminates are observed to increase due to the effect of moisture/temperature subjecte d to the suddenly applied uniform pulse loading. (C) 2001 Academic Press.