A family of models of hard and soft interfaces with damage

In many industrial applications in aeronautical, civil, energetic, automotive and biomedical engineering, adhesion techniques have recently emerged as assembly procedures alternative to conventional joining. Adhesive bonding is advantageous for many aspects, such as mitigation of stress concentration, better resistance to corrosion and water sealing, and the possibility of assembly dissimilar materials. In the literature, interface models are a classical modeling approach to the description of the mechanical behavior of adhesive joints. In this paper, an original generalized interface model is presented for both soft and hard adhesives, characterized by lower and higher stiffness than the adherents, respectively. The proposed model is able to capture a damaging behavior of the adhesive material, the elastic properties of which are obtained by homogenizing a microcracked media. The cracks density in the adhesive is the damage parameter, and a kinetic law based on the generalized standard material model describes its evolution. The role and relevance of damage velocity is illustrated through some simple examples and with a comparison with experimental data taken from literature. The numerical results show how the mechanical properties of the adhesive and the joint degrade as damage evolves, indicating a transition from quasi-brittle to brittle behavior as the damage velocity decreases.