Mechanical behaviour of adhesively bonded composite single lap joints under quasi-static and impact conditions with variation of temperature and overlap

The use of adhesively bonded joints in structural components for the automotive industry has significantly increased over the last years, supported by the widespread integration of composite materials. This synergy allows vehicle manufacturers to offer a significant weight reduction of the vehicle allowing for fuel and emissions reduction and, at the same time, providing high mechanical strength. However, to ensure vehicle safety, the crashworthiness of these adhesive joints must be assessed, to evaluate if the structures can sustain large impact loads, transmitting the load and absorbing the energy, without damaging the joint. The novelty of this work is the study of the strain rate dependent behaviour of unidirectional composite adhesive joints bonded with a ductile epoxy crash resistant adhesive, subjected to low and high testing temperatures and using different overlap lengths. It was demonstrated that joints manufactured with this type of adhesive and composite substrates can exhibit excellent quasi-static and impact performance for the full range of temperatures tested. Increasing the overlap length, and independently of the testing temperature, it was observed an increase of energy absorbed for both quasi-static and impact loads, this is of considerable importance for the automotive industry, demonstrating that composite joints exhibit higher performance under impact.