Characterization of Mechanical Adhesion Failure in Epoxy Nanocomposites by Acoustic Emission Method

Abstract

Polymeric nanocomposite coatings are used to protect metallic components in a variety of civil structures from corrosive agents. The adhesion between a coating and its substrate is not yet fully understood. In this study, the relationship between mechanical delamination of epoxy coating systems and the acoustic noise generated during failure was explored using acoustic emission. Three metrics were compared: a) mechanical loading data, b) post-test image processing, and c) acoustic emission data to gain insight into the coating-substrate layer. Neat epoxy and three epoxy nanocomposite systems modified with carbon nanotubes (CNTs), graphene (GNPs), and silica (SiO2) were casted on mild steel at two different thicknesses via draw-down bar. Test results demonstrated that there was a correlation between mechanical adhesion/cohesion strength and resulting acoustic noise. The findings suggested that the higher thickness in the reinforced coatings provided for a greater cohesion failure area as well as higher volume of acoustic energy.