X-ray diffraction and fracture based analysis of residual stresses in stainless steel–epoxy interfaces with electropolishing and acid etching substrate treatments

The aim of this study is to investigate the effect of a stainless steel surface condition on the thermal residual stresses at a bi-material interface. AISI 304 stainless steel–epoxy specimens with either as-received, nitric acid etched or electropolished substrates were prepared. Exact specimen curvatures and an analytical method were used to estimate residual stresses and the behaviour of the epoxy layer. X-ray diffraction stress measurement (XRD) was performed to determine the interfacial stress state. In addition, a method was developed to examine the interface fracture toughness of the specimens. Based on the results, the residual stress estimation at the interface was confirmed and the effect of the surface treatments on the interface fracture toughness was evaluated.