Abstract:
Throughout the modern world there is large shift towards a circular economy. Composite recycling is being increasingly researched throughout industry due to government incentives and increasing material demand. Mechanical recycling is widely considered to be the optimal modern solution to recycling glass fibre reinforced composites (GFRC) due to it meeting the low costs required from glass fibre reinforcement industry.
The objective of this research was to demonstrate the feasibility of mechanically recycling thermoset GFRC. End of life composites were mechanically recycled, and the ground fibreglass output was used as a filler material for polyester resin and thermoset GFRC. Ground fibreglass filled polyester resin samples and thermoset GFRC panels were manufactured and tested to understand the effect of the filler.
The first research aim was to understand the influence that the ground fibreglass filler had on polyester resin. This was to be understood through experimentation for the curing kinetics and tensile testing for the mechanical properties of polyester resin. The filler weight percentage and particle size were varied during both experiments. The ground fibreglass filler was found to have minimal effect on the curing kinetics of the polyester resin, and the tensile mechanical properties were found to be optimised at a particle size of 0 ≤ 150 μm at 10% filler weight percentage.
The next research aim was to understand the influence of the ground fibreglass filler within polyester resin once it had been introduced to thermoset GFRC. To understand the mechanical properties, three glass fibre types were researched: uni-directional, cross-directional, and random-directional at varying glass fibre densities and filler weight percentages. In general, it was found that an increase in filler above 10% weight percentage reduced mechanical properties. In fibre types with glass fibre bundles (unidirectional and cross-directional) this was due to the increase in viscosity of the filled resin not being able to permeate to the interior of the glass fibre bundles, creating an inferior matrix to fibre bond. This effect was worse for low density glass fibres as it was for high density. For random-directional fibre, an increase in weight percentage produced a reduction in mechanical properties due to the higher viscosity of the filled resin increasing the quantity of voids within the composite. The density of the glass fibre had no influence on this.
Overall, this study the demonstrated the feasibility of using up to 10% weight percentage of ground fibreglass filler at a particle size of 0 ≤ 150 μm within GFRC, making it a suitable avenue for composite recycling.