Fibre reinforced plastic composites (FRPs) are widely used in engineering applications but there is vast opportunity to develop high performance composites with a lower environmental impact. In this thesis, the use of bio based epoxy as a matrix material, microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC) as rigid particle reinforcement (toughening filler) and regenerated cellulose fibres as a continuous fibre reinforcement have been examined.
The three best performing commercially available bio based epoxy systems possessed good strength (> 68 MPa), tensile modulus (> 3 GPa), toughness (> 140 J m 2) and a reasonable Tg (> 70 °C) with bio based carbon content of 28 %, 39 % and 36.6 % respectively. These properties compare very well with conventional systems, and make them well suited for use in composite applications.
MCC and CNC were added to a partially bio based epoxy, at 10 wt. % and 5 wt. % respectively. Different dispersion techniques were performed, and efficacy was compared via thermomechanical and mechanical testing, image analysis of optical micrographs and fractography. For MCC, the best dispersion method was dry sifting, whereas for CNC modified resins three roll milling was more effective. Use of cellulose as particle reinforcement provides an increase in system bio based content, a modest increase to tensile modulus (10 % to 20 %) and a large increase in fracture energy (more than 100 %), at expense of the tensile strain to failure and hence tensile strength, which reduced by up to 10 %.
Continuous fibre composite panels were produced using a plain weave regenerated cellulose fabric within a partially bio based epoxy system. The resulting composite, with up to 78 wt. % bio content, shows much promise as it exhibited high tensile modulus and strength for a natural fibre reinforced composite, Et = 14.5 GPa ± 0.8 GPa and σt = 132.3 MPa ± 4.4 MPa respectively.