Viscoelastic analysis of creep response for uniaxially-compressed laminates with initial deflection including the effect of physical aging

The viscoelastic behavior of simply-supported, cross-ply and angle-ply laminated plates with a physical aging phenomenon is examined. The laminates considered are under uniaxial inplane compression and have various amplitudes of initial imperfection. The analysis is based on a geometrically nonlinear viscoelastic formulation. The effective time theory is employed to construct the stress-strain relations. By assuming every component of relaxation moduli in each lamina has the same aging shift rate, the analysis is conducted on the effective time scale. The stress function is obtained by solving the compatibility equation by the use of the Laplace transform and a numerical integration scheme. Deflection is calculated from the moment equation by the Oalerkin method in conjunction with the numerical integration. Numerical results for deflection history and edge shortening for the glass-reinforced vinyl ester lamiuate~ are presented. The effects of the physical aging, the pre-loading aging time, the amplitude of imperfection, the magnitude of loading, and the coupling relaxation moduli on the creep responses are illustrated in the numerical examples. Solutions based on the quasi-elastic approach are also presented for comparison. © 1998 Elsevier Science Ltd.