Predicting multiaxial stiffness degradation using uniaxial data — A model based on non-proportional experiments on a structural adhesive

In this work, multiaxial experiments on a structural adhesive with varying levels of non-proportionality are analyzed with a focus on the stiffness degradation process. A load level-dependent stiffness degradation model is employed that captures both, Young’s and shear modulus degradation. It was found that a multiaxial stiffness degradation can be modeled with good approximation as a superposition of the uniaxial stiffness degradations. Furthermore, the results indicate an insignificant influence of the level of non-proportionality on both Young’s and shear modulus degradation for the analyzed short fiber-reinforced adhesive. • Superposition of uniaxial data is sufficient to model biaxial degradation behavior. • Proposal of a versatile, load level-dependent stiffness degradation model. • The stiffness degradation is found independent of the level of non-proportionality.