In situ microscopic surface characterization studies of polymeric thin films during tensile deformation using atomic force microscopy

Atomic force microscopy (AFM) has been used to study the cracks developed on thin-film coatings on a polymer substrate subjected to external tension. To conduct in situ tensile tests in AFM, a special stage has been built. A new technique to image the same control area at different strains was developed and used to study the propagation of a crack with increasing strain in magnetic tapes. Metal particulate tapes developed numerous cracks of shorter length, perpendicular to the loading direction. In contrast, metal-evaporated tapes developed cracks that extend edge to edge. The variation of the crack width and the spacing with strain were measured and explained with the help of models based on elasticity.