Experimental study on the constitutive model of optically clear adhesive films under rapid loading

摘要

The mechanical properties of optically clear adhesive (OCA) films can be anisotropy and viscoelasticity, and they are distinguished from conventional linear elasticity and hyper-elasticity. These properties should be considered to analyze the interfacial stress, which plays an important role in evaluating the failure of a structure containing OCA. Based on well-designed systematical experiments in the material's principal axes, a phenomenological constitutive model of OCA has been proposed in a transversely isotropic and rate-dependent form. For the application to large deformation cases, the constitutive model was developed by using true stress and true strain. Results show that the well-known assumption of volume-incompressibility is not appropriate for OCA, and Poisson's ratio can vary with the loading rate and the current strain. Considering that the mono-axial mechanical behaviors along the material's principal axes present strong non-linearity, an incremental three-dimensional constitutive model has been developed for finite element method (FEM) implementation. By comparing with traditional isotropic elastic and hyperelastic models, numerical examination results show that the proposed constitutive model can give a more accurate description of experimental stress-strain curves.