Abstract
We present the initial steps towards formulating a multiphysics-based digital twin for predicting aging for multi-material adhesive step lap joints (ASLJs) that accounts for mechanical and environmental generalized loading. Initially, we provide a definition of the digital twin context and the particular digital twin architecture considered associated with the data-driven digital twin flavor. Subsequently, focus is given to establishing and exercising a theoretical and computational framework accounting for the degradation of properties for materials participating in ASLJs due to environmentally-aided damage accumulation. A thermodynamics-based theory is derived as a first step. An initial computational implementation of it is developed and applied to two models of multi-material ASLJs involving a titanium Ti-6Al-4V alloy and carbon epoxy composite adherent and an FM-300K adhesive. Several studies have been performed to identify the effect of parameters related to the choice of element order, mesh density, damage parameters and inclusion of damage models for the participating domains. Finally, the predictions obtained from the framework are compared with experimental results to establish the necessary validation for two environmental conditions of room and elevated temperatures at low ambient humidity. These results provide an initial insight into the characteristics of the aging degradation of ASLJ performance when both the adhesive and the composite material adherent are accumulating damage and contribute to aging of the respective materials.
