Situated strategically in most modern-day cars, passenger airbags are designed to protect against head and chest injuries in the case of a frontal collision. The full impact and safety of these airbags is achieved only in combination with the seat belt. The passenger airbag has a volume up to 150 liters depending on the size of the car. It is sewn with a woven fabric and comes in different shapes and stitches depending on the specific requirements of the vehicle.The present whitepaper studies the behavior of passenger airbags that are stitched with larger pleats. The pleat stitch is commonly seen in surgical masks (fig 1), and helps masks stretch to fit any person’s face, irrespective of the size. The objective of our study is to conclude with an improved version of passenger airbags to provide more cushion to the occupant in case of a collision. Pleat stitches insurgical mask and fabric is shown below.
A typical passenger airbag (PAB) is made with 2D Shell Meshing in Hypermesh with an average element size of 5mm. In our experiment, the pleats are captured in the main panel of the PAB. The flat PAB is then stitched into the Hypermesh using morphing techniques. Crush folding is performed on the stitched bag to ensure that it fits inside the package using simfolder in a visual safe. An approximate meshing is done to represent the Instrument panel (IP) and windscreen. The folded bag is positioned in the environment mesh and a deployment model is prepared in LS dyna. The segments with pleats are connected in the centre with Nodal Rigid Body (NRB). These NRBs will hold the pleats from being opened during deployment. The airbag deployment is done by corpuscular particle method(*AIRBAG_PARTICLE). Two deployment models have been prepared - one without NRBs so that the pleat segment will open, and second model with NRBs to hold the pleats throughout the deployment so that pleat segments will not open. Then, the results of the two deployments are compared. The volume of model 2 with NRB (pleats closed) is 118 Litres. The volume of model 1 without NRB (pleats open) is 122 Litres. As you can see, the pressure is higher in model 2 with NRB (pleats closed).
The volume of model 2 with NRB (pleats closed) is 118 Litres. The volume of model 1 without NRB (pleats open) is 122 Litres. As you can see, the pressure is higher in model 2 with NRB (pleats closed). Now, let us see what happens in case of a collision. When the PAB deploys, if the pleats are released at the right time, just as the occupant is pressing against the bag, the gas inside will spread through the pleat segments, providing far more cushioning to the occupants. This will protect them better from injuries. Naturally, model 2 without NRB delivers better protection.