Interface element including point-to-surface constraints for three-dimensional problems with damage propagation

An interface finite element for three-dimensional problems based on the penalty method is presented. The proposed element can model joints/interfaces between solid finite elements and also includes the propagation of damage in pure mode I, pure mode II and mixed mode considering a softening relationship between the stresses and relative displacements. Two different contact conditions are considered: pont-to-point constraint for closed points (not satisfying the failure criterion) and pont-to-surface constraint for opened points. The performance of the element is tested under mode I, mode II and mixed mode loading conditions.