Interfacial Fatigue and Discrete Interfacial Damage in a Finite Strain Thermomechanical Framework

We present a stabilized finite element method for thermomechanical problems in the class of materials with discrete microstructural interfaces that undergo interfacial fatigue and dominant interfacial damage. This formulation is applicable to polycrystalline solids, fibrous composites, filled elastomers, and additively manufactured layered materials. A finite strain formulation for monolithically coupled thermomechanical fields is presented where interfacial kinematic models for low-cycle fatigue and for strong interfacial discontinuities are variationally embedded at the interfaces. Formulation is written in the spatial configuration to account for large local strains and finite rotations of the interfaces. The method is implemented employing the family of low-order 3D Lagrange elements comprised of linear hexahedra and linear tetrahedra. A set of benchmark problems is presented to show the mathematical and algorithmic attributes of the method.