On the crack initiation along brittle viscoelastic adhesive layer in DCB test

Abstract

The double cantilever beam (DCB) test is commonly used to assess the adhesive layer toughness in pure mode I. But adhesives are polymeric materials which can dissipate energy by viscosity. In a previous paper, the investigation of the crack propagation along brittle viscoelastic layer in DCB test shows that the critical strain energy release rate a given crack growth rate is dependent on the loading conditions and on the current crack length. In this paper, the influence of loading conditions and initial crack length on the crack initiation is investigated through a large numerical test campaign. The DCB specimen is modelled as Timoshenko beams supported by a brittle viscoelastic foundation. Three different resolution schemes are used: (i) a Eulerian self-similar approach, Lagrangian approaches (ii) based on macro-element modeling and based on the inversion of the solution in the Laplace domain. It is shown that the latter approach is appropriate to the crack initiation analysis, and the crack initiation is strongly driven by the loading rate rather than the initial crack length. Thus, establishing a master curve describing the crack initiation conditions would make sense providing the appropriate dimensionless quantities are identified.