Description
More environmentally friendly propulsion concepts and the use of bio-based and carbon-neutral materials for structural, load-bearing applications are current endeavours in the field of sustainable mobility. Projects such as HAMMER, WoodC.A.R, Fortschritt, BioLIB and the Nano-Cellulose Vehicle Project have already demonstrated the feasibility of bio-based products for structural applications in the automotive industry. Bulky porous and foam materials are used in mobility as thermal and acoustic insulators, as sandwich cores for lightweighting and as impact energy absorbers. There is a strong need to provide the industry with alternatives to synthetic foams (such as EPS, EPP, PUR) derived from renewable resources that can compete in terms of physical properties and costs.Background:
The EU-funded BreadCell project is developing a novel biogenic foam derived from wood pulp. The project is investigating several aspects such as pore and fibre technology, fermentation technology, fire safety and potential applications, one of which is explored here: The BreadCell foam as an impact liner in a bicycle helmet.
Methode:
Several densities of the foam were characterised in terms of mechanics and morphology. The first included a dynamic characterisation using a split-Hopkinson pressure bar, the second high resolution scans with µCT. The explicit FEM solver LS-Dyna was used to construct a macromechanical material model of the foam. This material model was validated against simple drop tests using a hemispherical headform impactor. Once validated, the material model was assigned to the impact liner of a hard shell helmet. Multiple impact scenarios (inspired by the EN1078 certification test) were simulated with the baseline helmet (with a 70kg/l EPS liner) and the modified 'BreadCell' helmet (with a cellulose liner). Head loading was assessed in terms of peak acceleration and the Head Injury Criterion (HIC).
Results/Conclusions/Outlook:
The 'BreadCell' helmet passed the EN1078 test in the virtual environment - but higher liner densities are required compared to EPS. However, there is room for improvement as the morphological characterisation indicated a non-uniform density across the thickness of the foam. Further strengthening measures are currently investigated to increase the initial stiffness and consequently the lightweightness of the solution.
Period | 16 May 2024 |
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Event title | Paper&Biorefinery Conference 2024: PAPER INDUSTRY: renewable, responsible, ready for the future! |
Event type | Conference |
Location | Graz, AustriaShow on map |
Degree of Recognition | International |