Mechanistic model for the mechanical behavior of assemblies bonded with pressure-sensitive adhesives

The focus of this paper is on a modeling methodology for capturing the complex mechanical behavior of a single layer pressure-sensitive adhesive (PSA) system, based on empirical observations of its stress-strain behavior. This study is motivated by the fact that there is very limited modeling ability to mechanistically predict the bimodal stress-strain curves of single-layer PSAs. Empirical observations verify that this behavior is due to softening caused by nucleation and growth of cavities in the early deformation stage and hardening due to fibrillation during the final deformation stage before terminal debonding from the substrate. The effects of different loading conditions, including loading rate, stress and temperature, on PSA systems are also important. In-depth physics-based understanding of the connection between morphological changes in the joint and mechanical performance (including relevant failure mechanisms) of PSA-bonded assemblies will help to optimize PSA materials and joint architecture for maximum performance and durability. The goal of the mechanical modeling capability proposed in this study is to enable a virtual testing capability with reasonably high fidelity. The proposed modeling approach builds on an existing ‘block model’ methodology [1] and improves the existing approach by modeling each block with a strain-hardening viscoelastic constitutive model to capture the fibrillation process. Results show reasonable agreement between this improved mechanistic ‘block model’ and experiments. Such a mechanistic model can now be used as a virtual-testing tool, to explore how these PSA systems will behave on different substrates under different loading conditions.