Failure characterization of a structural adhesive
Strength vs. rate-of-strain data show accurate, viscoelastic time-dependence for a bulk epoxy adhesive (Metlbond 1113) in tension and shear, but not in the adhesively lap-bonded state. A detailed analysis of the lap shear joints, combining results from neutron radiography, scanning electron microscopy and roughness measurements, indicated the dominance of internal voids and stress concentrations not present in the bulk state. A qualitative fracture mechanics approach was used to reconcile the results. A general methodology to elucidate practical adhesive bonding problems is suggested that combines elastic, plastic and surface characterization.