Crash Analysis

When vehicles are subjected to impulsive loadings such as those experienced during a collision, impact or crash, the structure is deformed and forces are transmitted to the passengers. Fatalities will result when the structural deformations are large and when the forces experienced by an occupant are excessive. Under less extreme loading conditions an occupant may be injured, impairing the evacuation of the vehicle. To assess the severity of the loadings, computer simulations can be used to analyse both the structural response of the vehicle and the effect on passengers. The analysis of structural impact requires the use of specialised finite element programs that can take into account the effect of non-linearity, contact, material inertia, large deformations and strain rate effects.

Two recent projects highlight the group's work in this area. The first considered impacts on a range of assemblies taken from the fuselage of an airliner. The picture (right) shows the collapse of the cargo bay floor. All major components were modelled including frames, stringers, clips and skin panels. A full scale drop test of a section of fuselage confirmed the accuracy of the simulation results. The picture shows the structure below the passenger floor following a vertical impact. Under the impact loading the cargo bay floor deforms, and the accelerations and forces transmitted to the passengers were extracted from the analysis for post injury assessment.

The second project, addressed the crashworthiness of a concept composite fuselage structure. The principal effort was directed towards the development of methodologies for the modelling the joints between composite components. The large number of such joints within a fuselage structure and their potential effect on the overall deformation mechanisms imposed a requirement for a simple-to-implement, yet accurate methodology.