Effects of Elastoplasticity, Damage, and Environmental Exposure on the Behavior of Adhesive Step-Lap Joints

The presence of damage in the adhesive material as well as combined environmental excitation in multi-material adhesive step-lap joints (ASLJs) often encountered in aircraft industries are frequently neglected. Historically, the ASLJ design is based only within the scope of elastoplastic failure. The present work describes the implementation and application of a computational framework enabling the quasistatic performance evaluation of such joints under the simultaneous presence of plasticity, damage, and hygrothermal environmental stimuli. In particular, ASLJ linking Ti–6Al–4V alloy adherents with an FM-300K adhesive are modeled under the proposed framework for various material responses and environmental excitations. It is shown that the assumption of using only elastoplastic failure for the adhesive may not be an adequate assumption for designing and qualifying ASLJs. Specifically, consideration of the presence of plasticity, damage, and environmental effects indicates that there are reasons to re-examine the design practices of such joints and to determine the relevant material constants associated with the multiphysics cross-coupling effects.