Size effect in tension of thin films on substrate: a study based on the reformulation of mechanism-based strain gradient plasticity

We have used the type-II strain gradient plasticity theory, based on the Taylor dislocation model, to study the size effect in uniaxial tension experiments of a copper thin film on a Kapton substrate. There are two contributing mechanisms to the size effect in uniaxial tension of thin film on substrate. One is the strain gradient effect associated with the higher-order boundary condition, and the other is the substrate constraint effect on the yield stress. It is shown that the latter dominates the contribution to the size effect in uniaxial tension of thin film on substrate.