Racecar Engineering – September 2019

84 http://www.racecar-engineering.com SEPTEMBER 2019

TECHNOLOGY – COMPOSITES

‘The requirements to reinforce a composite

structure are very different to those required to

make a linen shirt,’ Fischer adds. ‘This is why we

have put a lot of development into how we spin,

twist and weave the yarn to achieve the perfect

surface coverage with a strong bond between

the fibre reinforcement and the matrix.’

Tailor made

These different twisting and weaving

techniques tailor the mechanical properties of

each fabric to its specific application, whether

that happens to be a surfboard, a pair of skis or

a piece of a racecar bodywork. ‘This gave birth

‘We work with flax

because its supply chain

has the required maturity

to provide consistent

quality over the years’

to our AmpliTex range which are very efficient

reinforcement materials based on the same

building blocks as other reinforced materials

using synthetic fibres,’ Fischer says.

Just like a ply of carbon fibre, AmpliTex is a

range of flexible flax fabrics, each exhibiting a

variety of different weaving patterns to achieve

specific properties. But although AmpliTex can

outperform glass fibre, how can its stiffness be

increased to compete with the likes of carbon

fibre? ‘For us, it’s not enough to compete with

glass fibre,’ says Fischer. ‘On top of the high

specific properties of flax, you also have a low

absolute density, which provides us with a

great material to build stiffness in thin-walled

applications. If instead of smearing the material

into the surface, you can organise it in a 3D rib

structure, you further emphasise this singularity

and boost the bending stiffness.

‘It’s like the veins on a leaf that reinforces

the membrane; achieving maximum

stiffness with minimal material,’ Fischer adds.

‘Benchmarking this against carbon, we can

match the performance in terms of specific

bending stiffness for thin-shelled components

even though we have a material with lower

intrinsic properties, because we create this rib

structure, or PowerRibs as it is called.’

The PowerRibs reinforcement effectively

adds a backbone to the AmpliTex flax fabric.

PowerRibs is made by the unique twisting of

flax fibres which then forms a thick yarn. This

yarn is used to create a grid which is then

bonded to the AmpliTex fabric.

Material world

Carbon fibre is incorporated into racecars in

several ways. For bodywork and aerodynamic

elements, plies of carbon fibre are bonded

together in different orientations to form a

laminate. Whereas, for more structural parts

such as the chassis and anti-intrusion panels

an aluminium honeycomb or foam core is

sandwiched together between two skins of

carbon fibre to satisfy these higher load cases.

‘When you want to maximise performance

per weight there are physical limits given by the

To bolster its mechanical properties the

AmpliTex fabric can be reinforced with a

grid structure which is called PowerRibs

Bcomp uses natural flax fibres to create its AmpliTex

range of fabrics. These are able to match the

performance of carbon fibre in certain applications