Techniques for the Mechanical Characterization and Numerical Modelling of Bonded Automotive Structures Under Impact Loads

The automotive industry is currently faced with increasingly strict requirements with regards to crash testing of its structures, which necessitates the development of powerful numerical tools that can reproduce high speed impacts and predict the behaviour of bonded structures under these conditions. The design of adhesive joints for quasi-static loadings is currently well understood, enabling the manufacture of strong, multi-material structures, essential for lightweight and efficient new vehicles. However, the design of impact resistant structures requires the determination of accurate models of the strain rate dependent behaviour of the materials used in vehicle construction. The work recently performed at the Advanced Joining Processes Unit (AJPU) at the Faculty of Engineering of the University of Porto (FEUP) and the Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI) has focused extensively on processes for high strain rate characterization of the mechanical behaviour of modern crash testing adhesives for the automotive industry. Special testing procedures and experimental equipment have been developed for the determination of strain rate dependent tensile and shear properties as well as fracture mechanics properties such as the fracture toughness. Special attention has been devoted to the study of mixed mode behaviour under impact conditions, with the design of a mixed mode apparatus for impact conditions. To enable the validation of cohesive numerical models based on the experimental data and allow for design optimization procedures, full scale testing of components has also been performed.