Analytical and Experimental Evaluation of Nonlinear Viscoelastic-Viscoplastic Composite Laminates under Creep, Creep-Recovery, Relaxation and Ramp Loading

Abstract

A numerical procedure to predict long-term laminate properties of fibre reinforced composite materials was developed. In the procedure, we extended the classical laminate theory to include time related response of composite materials for membrane and flexural loading. The material response, dependent on the stress history, was modelled using the Schapery single integral equation. The integrals were handled by an approximate method that uses the Prony's series and only requires the storing of the current stress and some internal strain components. An efficient semi-direct time-integration scheme, providing a stable integration process, was derived to be included in the numerical procedure. Comparisons of theoretical results were made with experiments conducted on composite materials under creep-creep recovery, relaxation and ramp loading.