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.
