Real world crash investigations show that the protection of lower limbs of a motor car driver in frontal impact is still a major problem.
Knees can hit rigid components behind the dashboard or the steering column (and risk some lesions like tibia or patella fracture) and the restraint systems available today still do not prevent the sub-marining effect.
For these reasons, FAURECIA has developed the PYROTECHNIC KNEE BOLSTER (PKB) which improves the lower limbs and pelvis protection and, thanks to its restraint action, improves the security of the car driver in a global way.
The design of the PKB allows to avoid the contact of the knees on the rigid parts and to absorb a part of the kinetic energy of the occupant of the car.
Its adjustment, according to the other restraint systems like the seat belt, the seat and the driver airbag gives to the car driver a high level of safety.
The PKB development is supported by a FAURECIA methodology (called the Continuous Safety Concept) used for the safety projects.
The early design phase is based on numerical studies with MADYMO software.
Simulations of a frontal impact tests at 56 km/h (03 oriented rigid barrier with 100% overlap) has been performed. Thanks to specific in-house tools, optimisation of the PKB design has been done with two frontal crash dummies: Hybrid III 5% and 50% drivers. These calculations were validated with experimental results on a sled test device.
The goal of this paper is to present the development and optimisation phases of the PKB and the profits in terms of safety.