Strain-rate effects on deflection/penetration of crack terminating perpendicular to bimaterial interface under dynamic loadings

Strain-rate effects on the deflection/penetration behaviors of a crack terminating perpendicular to a linear elastic bimaterial interface under dynamic tensile loadings are investigated numerically with the so-called Cohesive Crack Model and quasistatic material parameters. The competition between the deflection and the penetration is found to depend markedly on the loading rate (or the strain rate) and amplitude as well as the interfacial strength. The crack can penetrate through the interface only when the strain-rate is higher than a threshold value (or the critical strain-rate) which decreases with the interfacial strength, or else the crack will deflect into and then propagate along the interface; the minimum loading amplitude needed for the crack penetration increases with the strain-rate, and, startlingly, such a strain-rate dependence is found to be independent of the interfacial strength. Furthermore, two inferences can be drawn directly: one is that the second phase failure in composite materials or concrete can occur at high strain-rate, which has been observed experimentally by previous authors (Brara and Klepaczko in Int J Impact Eng 34: 424-435, 2007); the other is that the strain-rate effects of the dynamic failure strength of composite and concrete can be induced only by the structural response of materials, which sustains the argument proposed by Cotsovos and Pavlovic (Int J Impact Eng 35: 319-335, 2008).