Effect of the loading rate on viscoelastic interfaces with bridging fibers

Abstract

To investigate the mode-I failure of viscoelastic interfaces, novel tensile tests are conducted on rubber/fiber sheets with loading rates of 0.1–500 mm/min. Based on these tests, a new tri-linear cohesive zone model (CZM) is proposed. Different from the traditional CZM, the developed CZM is able to model the fiber bridging behavior as well as describe the loading rate dependence of viscoelastic interfaces. The previous CZM does not have this advantageous feature. In addition, the tensile experiments reveal that the bridging fibers exhibit pseudo-viscoelasticity. This refers to the fact that the mechanical properties of carbon fibers without viscoelasticity exhibit a loading rate dependence. To explain this, the concept of the “fiber bridging degree” is proposed, and a quantitative analysis is conducted using image processing techniques. The results indicate that the fiber bridging degree increases from 109.5 at a loading rate of 0.1 mm/min to 1747.5 at 500 mm/min. Furthermore, by combining the tri-linear CZM with a rheological model, a new constitutive model is derived, which can successfully simulate the mode-I failure of viscoelastic interfaces.