Passenger safety within vehicles is a priority for automotive companies in order to meet both the regulations and customer expectations. The safety critical materials, those used for absorbing energy during a crash, are simulated with FEA in order to design and improve components and to reduce the requirement for physical testing, which in turn saves on development time and cost. The simulation capabilities of Jaguar Land Rover were identified as lacking in accuracy for energy absorbing materials. Quasi-static and dynamic testing of expanded polypropylene as coupon samples and vehicle components was carried out to assess their stress-strain responses, energy absorption capabilities and strain rate effects. Using the properties within FEA the mechanical behaviour of the material was predicted and validated against the physical testing. Updated material models were implemented back into Jaguar Land Rover that fully incorporate strain rate effects and contain reliable, traceable input data. The material models require stress-strain curves, density, material modulus and un-loading characteristics. A test methodology has been implemented into Jaguar Land Rover for characterising energy absorbing materials, something that was previously unavailable. This includes the use of three machines, a low strain rate Instron 5800R, a high strain rate Drop Tower and a Very High Strain rate (VHS) testing rig; each used to understand the effect of compression testing at a range of strain rates and under decelerating/constant velocity impact conditions. Energy absorbing materials were sourced from two foam manufacturers. It was shown that different manufacturer’s material performed differently, even when supplied to the same requirement and manufactured from the same precursor. Computed tomography under synchrotron radiation was utilised to inspect material differences, identifying possible causes for stress-strain changes under compression. From the images a 3D mesostructural model was created to predict the material performance during deformation. As a result Jaguar Land Rover procedures were changed, increasing FEA capabilities and increasing the utilisation of foam within the vehicle. New test procedures were implemented for characterising future energy absorbing materials. The simulation and computed tomography work will help towards the understanding of foam compression mechanisms.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:737677 |
| Date | January 2016 |
| Creators | Carnegie, Craig Robert |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/98790/ |
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