In modern passenger vehicles the A-Pillar is an important structural safety component. In full frontal, frontal offset-, pole and rollover collisions the APillar is carrying to a large load in order to minimize the deformation of the occupant compartment. Generally the larger the cross-section the more load the A-pillar can transfer. However, the A-pillars in general more or less reduce the forward vision angles for the driver. Therefore the width and strength of the A-Pillar are important vehicle safety parameters. The strength and size requirements on the A-Pillar are in contradiction. In an A-pillar design in which the cross section is folded and expands when needed the conflicting requirements can be combined in one component. As a normal state the cross-section of the component is folded, obscuring less of the driver’s visibility compared to a state of the art A-pillar. In a crash the A-pillar expands which results in a significant increase in the cross section. The expanded cross section increases the strength of the A-pillar. An expanding A-pillar can be accomplished by pressurizing a folded structure. A cost- and weight-efficient way to generate over pressure is by pyrotechnics (gasgenerators)

An expandable A-pillar design was developed in which the conflicting requirements high strength and small cross section were combined in one component. The goal was to develop an A-pillar that obscure less of the driver’s vision in the normal operation, is lighter and has the same crash performance as a state of the art A-pillar. The development was carried out by combining mathematical simulations and mechanical crash tests. For the development of the expandable A-Pillar a mathematical sub structure model was developed and validated. The model was validated by comparing predictions from the model to results from a mechanical crash test. The expandable A-Pillar was mounted in the sub structure and the deformation performance was evaluated relative to the performance of a state of the art A-Pillar. The deformation force is less than or equal to the deformation force of a vehicle with a state of the art A-pillar. The obscuration angle is reduced by more than 25% (for left hand side A-Pillar from 12.3 – 8.9 degrees) and the mass is reduced by 8% (excluding mounting brackets and gasgenerator) relative to a state of the art A-pillar. The expandable A-pillar combines the conflicting goals, high strength, small cross section and low mass.