The structural properties of paraffin wax based hybrid rocket fuels with aluminium particles

Paraffin wax has been identified as a feasible high regression rate hybrid fuel. For this reason, paraffin wax needs to undergo stringent performance measures to qualify it to meet the requirements necessary for a large scale launch vehicle. Energetic additives such as aluminium powders have been considered for their performance enhancing possibilities. This research focusses on measuring the structural performance of the fuels similar to what would be required for a solid propellant. Thus, structural properties of both pure and 40 W t% aluminised fuels are investigated. Additionally, both elastic and plastic structural properties of the fuel need to be determined for complete material characterisation. Strain rate and temperature dependence of the material structural properties are investigated in this work through compression and tension testing. Results indicate that the addition of aluminium increases the strength of the fuel. Also, a slight increase in temperature was seen to decrease the structural performance significantly. This means that the rate of thermal propagation within the fuel grain is an important consideration. Finally, strain rate dependence is evident in paraffin wax. Higher strain rates result in higher Ultimate Tensile Strength (UTS) failure points, at lower levels of strain.