The Influence of Loading Rate on the Strength of Composite Materials

Abstract

Experimental evidence shows that, in different loading rate regimes, a fiber-reinforced composite exhibits different failure modes. A unified model is proposed to account for these observations. In the low loading rate regime, damage accumulation is the fundamental failure process, whereas in the high loading rate regime, failure of the weakest site determine the strength. Both are nucleation controlled processes. As a result, the rate limiting theory (kinetic theory) is used to derive the relationship between the ultimate tensile stress and the loading rate. The failure process in the transition regime is also explained by taking into account the local stress enhancement near the failure zones. This is equivalent to imply a strong defect interaction existing in the transition regime. Theoretical predictions are found to be in good agreement with experimental data.