Modifying Composites for Hydrogen Tanks
Hopia, Karoliina (2021)
2021
Materiaalitekniikan DI-ohjelma - Master's Programme in Materials Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2021-10-01
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202108306870
https://urn.fi/URN:NBN:fi:tuni-202108306870
Tiivistelmä
Fuel cell vehicles can be a green option to replace conventional internal combustion engine cars. To achieve large scale commercialisation, lightweight and reliable gas tank materials are needed. Currently there are metallic and composite tanks, and their hybrids, for storing hydrogen. The latter have the advantage of being lightweight, thus more suitable for transportation applications. Carbon fibre composites are a promising option for novel material development. The aim of this thesis was to test how two carbon fibre modifications and using graphene oxide (GO) as a filler affect mechanical properties and barrier properties of laminates.
The key properties for a hydrogen tank are barrier properties, good adhesion between matrix and fibres, glass transition temperature and at the manufacturing step, the resin viscosity. In the thesis, an ionic liquid (IL) epoxy and GO were characterised. Carbon fibre laminates were made from a commercial epoxy and IL epoxy, modified carbon fibres and GO and compared with unmodified reference laminates. The test chosen for the comparison was internal shear strength (ILSS) according to ISO 14130 standard. Barrier properties are considered at theoretical level.
The chosen lamination technique left porosity in laminates, which was affected failure mechanisms of reference laminates.IL laminates had issues with the mixing ratio and the surface and laminates were invalid. While results were inconclusive, methods were optimised, and discarded possibilities were proven ineffective. Future actions could be planned using the acquired knowledge.
The IL epoxy had clearly lower viscosity and Tg than the commercial epoxy. However, the Tg of IL laminate was above the operation temperature for hydrogen tanks. Fibre modifications did not show an increase nor significant decrease of ILSS of reference laminates. The GO containing laminate with unmodified fibres showed the best ILSS when normalised against fibre fraction, which indicated that GO was reinforcing the laminate.
The key properties for a hydrogen tank are barrier properties, good adhesion between matrix and fibres, glass transition temperature and at the manufacturing step, the resin viscosity. In the thesis, an ionic liquid (IL) epoxy and GO were characterised. Carbon fibre laminates were made from a commercial epoxy and IL epoxy, modified carbon fibres and GO and compared with unmodified reference laminates. The test chosen for the comparison was internal shear strength (ILSS) according to ISO 14130 standard. Barrier properties are considered at theoretical level.
The chosen lamination technique left porosity in laminates, which was affected failure mechanisms of reference laminates.IL laminates had issues with the mixing ratio and the surface and laminates were invalid. While results were inconclusive, methods were optimised, and discarded possibilities were proven ineffective. Future actions could be planned using the acquired knowledge.
The IL epoxy had clearly lower viscosity and Tg than the commercial epoxy. However, the Tg of IL laminate was above the operation temperature for hydrogen tanks. Fibre modifications did not show an increase nor significant decrease of ILSS of reference laminates. The GO containing laminate with unmodified fibres showed the best ILSS when normalised against fibre fraction, which indicated that GO was reinforcing the laminate.