Experimental investigation and numerical modelling of the mechanical response of a semi-structural polyurethane adhesive

The use of adhesives in load-carrying structures and components has increased recently, especially in the automotive industry. There has been many studies on structural adhesives, but when it comes to semi-structural adhesives, there is a lack of literature. In this article, a semi-structural two component polyurethane adhesive has been studied experimentally and modelled numerically. It was performed uniaxial tension tests at rates ranging from 10(-3)s(-1) to 10(-1)s(-1). The tests were monitored by two perpendicular digital cameras and a thermal camera. Similarly, uniaxial compression tests were performed at rates ranging from 10(-3)s(-1) to 350s(-1), where a split Hopkinson pressure bar (SHPB) was used for the highest rates. The low-rate tests were recorded with high-resolution digital cameras, while a high-speed camera and a thermal camera were used for the SHPB tests. In addition, it was performed notched tensile tests at a low rate to study failure. These tests also served as a validation case for the numerical simulations. A high-resolution camera was used, such that the local strains in the notch could be captured using digital image correlation. The experiments indicated that the adhesive behaved similar as rubbers. Therefore, the Bergstrom-Boyce constitutive model was applied in the numerical simulations. The overall prediction of the test results was seen to be satisfactory, but the initial stiffness was too high compared to the response measured from the experiments. An investigation of the numerical results indicated that this mismatch was likely linked to the formulation of the inelastic shear rate.