The visco-damage mechanical response of swirl-mat composites

This article concerns the characterization of the mechanical response of composite materials made of continuous, randomly oriented strands ('swirl-mat') of E-glass fibers embedded in a urethane matrix. The purpose of this work is to identify and quantify the various parameters that govern the material response in order to develop a predictive model. The characterization is based upon creep data collected during the application of constant load of several amplitudes and various durations, and recovery data collected after load release. The glass-fiber/urethane matrix swirl-mat composites were observed to develop distributed damage in the form of profuse internal micro-cracks, they exhibit time-dependent response and develop permanent deformation upon load removal. A one dimensional model is presented, which incorporates the foregoing features of creep, continuum damage, and permanent deformation. The model is employed to represent the characterization data as well as to predict the response under two-step load histories.