Numerical simulation for the tensile failure of randomly oriented short fiber reinforced plastics based on a viscoelastic entropy damage criterion

In this study, we conduct a numerical simulation of the tensile failure of randomly oriented short fiber reinforced plastics (SFRP) by integrating an entropy damage criterion. The Mori-Tanaka theory is used as the model for the composite. The constitutive equation of the resin is defined by a conventional viscoelastic model with a power law considering entropy damage. The dissipated energy is calculated using this constitutive equation and the stress-strain history. Dividing the dissipated energy by the absolute temperature yields an entropy value, which is related to material damage that results in a decrease in the elastic moduli. This deteriorating behavior of the resin is integrated into the Mori-Tanaka theory. The tensile failure simulation is implemented at nine angles ranging from 5° to 85° in 10° increments to determine the relationship between the tensile strengths and off-axis angles. These results are introduced into the layer wise method (LWM) and superimposed to obtain the tensile strength of randomly arranged short fiber reinforced plastics. The calculations are performed by varying the strain rate. The numerical results are in good agreement with the experimental results. Thus, the originality of this study is the introduction of a viscoelastic entropy damage criterion into a conventional micromechanical model.