Master of Philosophy (Materials Engineering)
School of Mechanical, Materials and Mechatronic Engineering
Moriana, Alain David, Fabrication, characterisation and optimisation of shear thickening fluids, Master of Philosophy (Materials Engineering) thesis, School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, 2016. https://ro.uow.edu.au/theses/4779
This thesis focuses on quantifying the effect of ingredients within shear thickening fluids (STFs) with resultant rheological behaviours for their potential use in practical applications. This was done by firstly using steady shear testing to measure the rheology of STFs fabricated by several carrier fluids of poly(ethylene glycol) and poly(propylene glycol) of varying molecular weights and fumed silica with different particle sizes. It was discovered that larger particles increased the thickening effect, critical shear rate and the specific carrier fluid used affected the overall shear thickening effect and the critical shear rate. It was found that the fumed silica at larger particle size (OX50), increased the thickening effect and critical shear rate and the type of carrier fluid used affected the shear thickening performance and the critical shear rate. It was also found that there existed an optimum weight fraction of fumed silica which showed maximum shear thickening performance. An explanation was then proposed to correlate factors such as varying particle size, carrier fluid chemistry and weight fraction to resultant rheological behaviours. A mathematical model was also proposed that correlated temperature and weight fraction to specific rheological parameters.
In two selected STFs from the initial experiment (“PEG400 + 45 wt% OX50” and “PPG400 + 35 wt% OX50”), various additives (Tubular and platelets of boron nitride and titanium dioxide) were used in attempt to improve shear thickening performance. Boron nitride (BN) particles, in particular, showed improved temperature stability of rheological behaviour during steady shear testing at 0.5 wt% in PEG400 + OX50. It was proposed that the superior thermal conductivity and hydrophilic nature of BN allowed for heat to rapidly evacuate from the STF during testing.
These findings have significant impact in helping to understand the effects of particles and carrier fluid chemistry on the shear thickening effect and assisting in ‘tailoring’ STFs for specific applications to maximise shear thickening for above mentioned applications.