Detachment Dynamics of Heterogeneous Adhesive Pads

Variations of material properties along fracture planes play a crucial role in crack propagation behavior. During detachment of adhesives, local perturbations of the crack front are observed, but the mechanisms occurring at the interface remain elusive. This thesis investigates how shapes of different fracture toughness on fracture planes can impede crack propagation. Five patterns are studied (horizontal, vertical and sinusoidal bands, check and crescent shapes). We assess the behaviors of cracks propagating dynamically under shear loading conditions (Mode-II). We use a spectral formulation of the boundary integral equations for simulations, and an adapted setup is created for experimentation. We show that spatial patterning of adhesive strength leads to various responses regarding effective toughness. In most cases this work covers, an increase in the characteristic size of heterogeneity slows crack propagation. We also report a toughening effect for some specific patterns. An interplay between front deformation and local speed variation might explain the slowing mechanisms observed. From preliminary results, it seems that shocks at the crack front that are not compensated by local deformation increase the amount of wave radiation to the bulk. Over the total energy provided to the system, less energy is purely dissipated for fracture, and we observe a slower propagation. In this work, we provide a quantitative evaluation of the ability of certain distributions of toughness to deflect crack propagation.