Analysis of stiffness of adhesive joints in car bodies

Adhesive bonding of joints in car bodies is known to contribute significantly to increased body stiffness. Although analytical techniques are able to give some prediction of this enhancement, the accuracy of the models is limited by the relatively low resolution of the joint details. Numerical models based on finite element analysis have been used to model different joint configurations and their predicted stiffness characteristics have been validated by experimental testing. It is shown that the joint stiffness of coach (T-peel) joints is critically dependent on the presence of fillets and flange bend radii. The application of stiffness data from ‘micro-models’ of joints into the prediction of full body behaviour presents computational problems due to the large number of elements in the FE analysis and the associated processing time. Various substitution element methods have been considered and a novel approach has been developed based on an undercut element concept. This technique enables the designer/modeller to easily include corrections for different joint parameters in the analysis of structural details in full body behaviour without the need for extended computing requirements.