Quick Prototype Methodology for Low Offset Thermoplastic Pedestrian Energy Absorbers

Abstract

This paper describes a methodology to prototype and validate thermoplastic energy absorbers in a broad range of vehicle geometries. The objective of this prototype tool designed with quick prototype methodology is to achieve ready PC/PBT energy absorber designs for pedestrian testing. Generic vehicle models were used to finalize the energy absorber design features. The prototype tool was designed from optimized energy absorber designs that meet pedestrian performance in low packaging space, typically 45-60 mm. A set of prototype tools is being built to match different beam heights and packaging spaces. The tool has also the functionality of achieving different thickness and different design features using the latest manufacturing technologies. A full energy absorber can be built from individual lobes over the width of the car. The finalized design combined with ‘quick prototyping’ methodology was used to finalize the mold design, which can cater to a wide range of vehicle geometries. The prototype designs were validated for different virtual car models. Correlation test was performed between FEA models and prototype molded parts using equivalent rigid impactor test. INTRODUCTION Each year about 7,000 pedestrians are killed and several thousand injured in the European Union due to pedestrian-vehicle accidents. The percentage of pedestrians injured each year across the globe is around 2% of the 2.9 million total persons injured in traffic crashes. On average, a pedestrian is injured in vehicle crash every 7 minutes. Pedestrian fatalities have gone down by almost 16% over the last 10 years. This has happened due to greater awareness toward driver safety. Additional improvements need for every vehicle to be pedestrian friendly. Pedestrians are much more vulnerable than car occupants when a crash occurs. Studies have revealed that vehicle styling and front bumper design affect pedestrian injuries. Accident investigation shows that there are three areas of the pedestrian body which are most subjected to injury, and each of these is subjected to a particular area of the car. The head is usually injured by the hood, fender top and A-pillars; the pelvis and upper leg by hood leading edge; and the knee and lower leg through contact with the bumper. Looking at the pedestrian injury statistics over past years The European Union and the Japanese government have both issued guidelines to assess the risk to pedestrians from passenger cars during an accident. The European New Car Assessment Programme (EURO NCAP) has developed some test procedures geared towards protecting pedestrians (see Fig. 1 & 2). EURO NCAP uses an approach similar to that given by The European Union. The lower leg test is performed by impacting the vehicle with a lower leg impactor at 40 kph (25 mph). Performance is measured in terms of acceleration, rotation, and shear of the lower leg impactor during the impact. Vehicle star ratings are assigned based on performance. 2006-01-1659 Quick Prototype Methodology for Low Offset Thermoplastic Pedestrian Energy Absorbers Ankit Garg and Gopi Krishna Surisetty GE Global Research Stephen Shuler, Mike Mahfet, Eric Jaarda and Frank Mooijman GE Advanced Materials Copyright © 2006 SAE International