Investigation on the ratcheting strain and cyclic softening of viscoelastic soft adhesive under uniaxial and biaxial cyclic loadings

Abstract

Uniaxial and biaxial multi-path cyclic loading experiments were carried out using the plate dumbbell-shaped specimens and the cruciform-shaped specimens prepared by silane-modified polyurethane adhesive, respectively. The uniaxial testing results showed that the stress–strain curve of the material was nonlinear, and its mechanical properties were viscoelastic. The adhesive exhibited cyclic softening and cyclic strain increase (cyclic creep and cyclic strain accumulation) under the tensile cyclic loading. The biaxial multi-path testing results showed that the non-proportional loading path caused additional ratcheting strain, which was related to different loading paths. According to the experimental observation, a uniaxial cyclic constitutive model was proposed. Furthermore, a biaxial cyclic constitutive model of the material was developed by introducing the loading path coefficient. By comparing the model prediction results with the experimental data, it was shown that the evolution of ratcheting strain and cyclic softening of the material under uniaxial cyclic loading was accurately described using the proposed model. Also, the biaxial cyclic constitutive model can well predict the mechanical behaviors of silane-modified polyurethane adhesive under biaxial multi-path cyclic loading.