Experimental and numerical study of the dynamic response of an adhesively bonded automotive structure

Based on economic and environmental factors related to energy efficiency, the automotive industry is being increasingly encouraged to design lighter structures, making use of adhesive bonding in vehicle body frames. To meet the standards of the automotive sector, adhesive joints must provide high strength and stiffness, low cost and good energy absorption at a component level, thereby ensuring good impact strength and passenger safety. This work aims to study, at room temperature (24 degrees C), the impact response of a real scale automotive structure bonded with a crash-resistant epoxy, allowing to access the suitability of adhesives for automotive structural purposes. The epoxy adhesive was found to successfully transfer the loads to the aluminium substrates and not to compromise the integrity of the structure, as its failure was dominated by the behaviour of aluminium. Results obtained with a numerical model of the component were found to be in close agreement with the experimental failure load, demonstrating that numerical analysis can be a viable tool to predict the structure's behaviour. In addition, a polyurethane was used as an alternative to the epoxy system to bond the structure, proving that the joint behaves better in the presence of a more flexible adhesive, as no failure was found for this case. Aluminium single-lap joints with two adhesive thicknesses were tested as a complement to understand the influence of this parameter on the impact response of a joint, showing a 21% decrease in strength when the highest thickness was used.