Graphical solutions to bond capacity and bond-slip behavior of pull-off/out joints with various adherents, adhesives, and substrates

Abstract

This study investigates the bond capacity and bond-slip behavior of pull-off (lap-shear) and pull-out joints with various adherents, adhesives, and substrates, filling the research gap in existing models that fail to account for the adherent nonlinear stress–strain behavior. A “Wine Glass model”, offering an elegant graphical and analytical solution to computation of bond capacity, is proposed. This model relies on two key assumptions: (i) a sufficient bond length (longer than an effective bond length) and (ii) a monotonically increasing stress–strain behavior of the adherent. The adherent stress–strain (σ-ε) curve and the stress axis (σ-axis) can be visualized as a wine glass. In this analogy, the interfacial fracture energy divided by the adherent thickness (Gf/t) represents the wine poured into the glass. The resulting height of wine corresponds to the adherent tensile stress, with respect to the bond capacity (Fb). The Wine Glass model unveils the mechanism governing bond capacity. Based on the Wine Glass model, an intuitive bond-slip post-processing method, which features a graphical solution as well, is then introduced. The Wine Glass model and associated bond-slip post-processing method are validated on pull-off/out tests corrected from literature, involving linear and nonlinear adherents, linear and nonlinear adhesives, and various substrate materials.