Reactive coarse-grained MD models to capture interphase formation in epoxy-based structural adhesive joints

Adhesive joints offer a superior strength-to-weight ratio compared to conventional fastening methods, making them essential for achieving cost-efficiency and sustainability goals. The adherends influence the adhesive in their immediate vicinity, creating regions with altered microstructures. These regions, known as interphases, exhibit material properties that differ from those of the bulk adhesive and are not fully understood from an engineering perspective. To address this issue, we introduce a novel coarse-grained molecular dynamics (CGMD) model for adhesive joints, which aims to study the interphase formation and its resulting properties at the molecular level. We utilize a reactive epoxy model from the literature for the adhesive and implement matching aluminium substrates, along with the necessary adherend-adhesive interaction parameters. The resulting adhesive joint model allows us to investigate the formation of the adhesive’s microstructure during the curing process and the mechanical properties of the joint. We conduct a parameter study on the adherend-adhesive interaction parameters, unravel the role of grafting bonds and their distribution, and examine the impact of the adhesive’s thickness. Additionally, we identify an interphase based on variations in the local microstructure, estimate its size, and determine the influencing parameters. In this first contribution, we demonstrate the capabilities of our model in evaluating the mechanical behavior of the interphase, which is crucial for gaining a better understanding of adhesive joints.