LAUSR

Abstract The present work addresses two key issues relating to the study of rate effects in adhesively bonded joints. Firstly, the accurate determination of the crack tip strain rate and secondly the accurate determination of cohesive zone length. The rate-dependent fracture behaviour of adhesive joints bonded with either a toughened epoxy or a ductile polyurethane adhesive was investigated under mode I loading rates ranging from 0.1 mm/min to 1.0 m/s with digital image correlation (DIC) analysis. The traction-separation laws (TSLs) were determined by measuring the J-integral values and the crack tip opening displacements simultaneously. An analytical method is proposed to correlate the crack tip opening velocity with the external loading rate. The lengths of the cohesive zones were measured, and the values were examined by thickness-independent and -dependent models. It was observed that the cohesive properties of the two adhesives exhibited very different rate dependences. An analytical tool is developed for the determination of the strain rates for TSLs using a direct method such as DIC.