In-situ birefringence microscopy of uniaxially stretched metal–polymer laminate

This paper concentrates on revealing the local deformation as a function of applied strain in a polymer coating supported by a plastically deforming and roughening metal substrate. To this end in-situ birefringence microscopy measurements have been executed. The measurements are performed in reflection and an alternative unwrapping scheme for the optical path difference is proposed. From the characterization of PET (polyethylene terephthalate) coated stainless steel it is concluded that strain localization appears below the macroscopic strain at yield and that the surface roughness of the substrate is the driving force of the localization.