During side-impact accidents there are few structural components between the vehicle occupant and the outside environment. Nevertheless. the number of structural components involved in resisting intrusion of the bullet vehicle is potentially large. Assessing which comporrents to modify so as to improve both the structural performance of the vehicle and reduce potential occupant injuries is a task performed most effectively by cornputer simulation.

Cranfield Impact Centre have developed techniques for predicting the structural performance of a car during side-impacts and the resulting car motion and occupant kinematics. First, a hybrid approach to predicting the structural behaviour of car sidestructures is used. Here, the structural and energy absorbing components and joints are tested to determine tlrcir non-linear behaviour (providing a data bank of information which can be invaluable in subsequent design procedures). This non-linear information is then input as data to the CRASH-D program to analyse a coarse finite element mesh of the side of the car and hence predict its structural characteristicsd uring sidc-impacts. The motion characteristics of the side-structure and car centre of gravity can then be predicted. Finally, the kinematics of the occupant and his likely levet of injuries, due to his interaction with the intruding side-structure, can be predicted using the Calspan CVS program.

These simulations allow the influencc of a large number of structural variations to be quantitied rapidly and cheaply. Consequently, structural improvements which rcquire changes to the least number of components can bc identified and impressive improvements in side-impact performance can be achieved without gross increases in car weight.

This paper demonstrates the use of these techniques and discusses measures which can improve side-impact performance.