Micro- and nano-morphological modification of aluminum surface for adhesive bonding to polymeric composites

Abstract

The aim of the present study is to demonstrate the effect of micro and nanomorphological modifications of aluminum surface on adhesion strength. While former studies have investigated surface morphological changes after employing various surface treatment methods, this study proposes a micropatterning method to provide designed surface topography for adhesion strength enhancement. An oxalic acid-based anodizing process was also applied after micro-scale patterning on aluminum surface to incorporate nanopores into the micropatterned surface topography. The adhesion strength of an aluminum/composite bond was assessed in terms of interfacial fracture toughness under various mixed-mode loading conditions using a single-leg bending test. Microscale periodic grooves incorporated with nanoporous surface morphology significantly improved the adhesion strength. Although bond strength enhancement can be attained in any mixed mode loading condition, the surface topography modification technique is more effective in sliding mode dominant loadings than in opening-mode dominant loadings. The bond strength improvement is explained by the increased implementation of mechanical interlock mechanism which increases the resistance for crack growth by altering the trajectory of crack propagation from the bi-material interface toward the polymeric composite.