WHAT ARE MULTIAXIAL REINFORCEMENTS?
Multiaxial reinforcements are fabrics made up of
multiple plies of parallel fibres, each laying in a different
orientation or axis - hence the term 'multi-axial'. These layers are
typically stitchbonded (usually with a polyester thread) to form a fabric.
Commonly used as a reinforcement within
composite structures, "multiaxials" or "non-crimp
fabrics" as they are known in the USA, effectively allow the composite manufacturer to
process multiple layers of unidirectional fibres (the optimum fibre
form) in a single fabric.
The advantages over traditional forms of reinforcements such as woven rovings are now widely accepted:
- The reinforcing fibres can be placed in different axis to optimise the performance of the finished laminate.
- No resin-rich areas mean that it is easy to
achieve a higher weight fraction (wf).
- Non-crimped fibres mean higher tensile and
flexural properties in the finished laminate.
- Reduced print-through, this is especially important on
boat hulls and automotive applications.
- Fabrics are easier to cut and handle as the
stitching holds the material together.
- Heavier combinations are possible, meaning
higher deposition rates.
- The straight uncrimped fibres within a multiaxial fabric allow good resin penetration and flow which is ideal for
infusion and light-RTM, whilst the stitching aids resin migration through the
layers (Z-direction) perfect for maximising infusion rates.