Development of novel flax bio-matrix composites for non-structural and structural vehicle applications

Abstract

The use of natural fibres (e.g. flax, hemp etc.) instead of synthetic fibres (carbon and glass etc.) as composite reinforcements not only benefits the environment, but also provides economical lightweight products for transports. Although there are a few studies reported in literature on use of flax fibres, there is no comprehensive guide on use of flax fibres with bio-resins to re-engineer bio- composite systems that can be used in vehicle structures. The state-of-art of the current research towards using natural fibre reinforced composites is reviewed by the thesis. The review covers the performances of flax composites, concentrating on the effect of matrix types and existing development methods. The review also identifies the rational of selecting tannin resins and bio-epoxy resins to combine with flax fibre reinforcements. In the experimental work, mimosa tannin resin (natural phenolic resin) and pine- oil derived supersap epoxy resin are selected to manufacture the fully renewable flax composites. By tailoring the fibre configurations and chemical surface treatments, the resultant composites were investigated to provide information for engineers to understand the composite behaviours and properties. Mechanical properties (tension, flexural, shear, impact etc.) and physical properties (moisture, ageing etc.) were assessed through adequate tests and analysing methods. In addition, bio-sandwich structures based on the novel studied composites and commercial bio-foams were evaluated to study the energy absorption which could be very important in vehicle design. Based on the results, flax/supersap epoxy and flax/tannin composites are suitable for possible exterior structural and interior non-structural applications, respectively. The developed flax fibre composites with innovative bio-matrices have a potential to prevail in modern vehicle applications, due to the competitive performances, economic viability and environmental acceptability.