A simplified and semi-analytical bolted joint model for crash and impact simulations of composite structures

In this study a simplified empirical approach is developed to describe the overall behaviour of a composite bolted joint for explicit crash and impact simulations. Based on analytical equations, classical laminate theory and empirical factors, a trilinear force-displacement curve is proposed for bolted joints under in-plane loads. The empirical factors are derived from single-lap shear experiments of carbon fibre prepreg specimens (Hexcel M18-1/G939) with different fasteners. Quasi-static and high-rate dynamic tests are assessed and two main influencing factors for the differences in the overall load levels are identified: the fastener type (solid/hollow rivet) and head type (protruding/countersunk head). Based on these results, a novel generalised model is developed, which prevents expensive physical and virtual testing for a variety of possible fastener/material configurations and significantly reduces the modelling effort. It is shown that the analytical and empirical expressions can easily be adapted in commercial finite element codes such as Abaqus/CAE and rely on few user input parameters.