Experimental and numerical study of rate-dependent mode-I failure of a structural adhesive

ABSTRACT We present an experimental and numerical study of the rate dependence of the mode-I failure of adhesive joints, focussing on aluminium plates bonded with Araldite® 2015. For the experimental part, we tested 24 double-cantilever beams (DCB) at six different prescribed speeds, from 0.1 to 5000 mm/min. The numerical simulations use a previously proposed cohesive-zone model (CZM) based on fractional viscoelasticity and a novel finite element combining a Timoshenko beam and an interface element. The CZM had previously been validated for a rubber interface, so here we present a procedure to identify its input parameters and validate its capability to predict the failure of joints made with an epoxy adhesive. An effective procedure is also developed to evaluate the dependence of the fracture energy on the crack speed without experimentally measuring the crack speed. The adhesive response was found to be markedly rate dependent. Within the range of tested speeds, the fracture energy of the adhesive more than doubles its value and the shape of the ‘fracture energy-crack speed’ curve resembles a sigmoidal shape, but more tests are needed at higher speeds to better determine the maximum value of the fracture energy and the actual shape of the complete curve.