Metal-adhesive bonded systems: Adhesion measurement using a three point flexure test

Single metallic adherend-adhesive bonded specimens are subjected to a three point flexure test in order to investigate the effects of adherend surface conditioning and adhesive curing conditions on the mechanical properties of the substrate-adhesive interfacial region. The main advantage of this test over more conventional ones (i.e. peel, tensile, shear tests) is to induce stress concentration which is responsible for a failure locus within the interfacial region and consequently its ability to provide data representative of practical adhesion in an adhering system. The results obtained are shown to be independent of adherend thickness, adhesive layer thickness, width of the bonded area and displacement speed used during testing. Data presented here are relative to Ti-6Al-4V titanium alloy/epoxy systems. They demonstrate the high sensitivity of the flexure test to the effects of prebonding treatments (chemical etching, anodization) and of adhesive curing conditions on practical adhesion.