aerospace
The extent to which
composites are
proliferating is highlighted
by this view of the 787
production area
make the first items in series production here, which
gives them confidence; and we can also assist at the
start, while they are waiting for their production
equipment to arrive. Our perception is that there is a
shortage of fabrication capacity in the UK; we have this
facility available, and people can use it.’
And just how many people will use it? Or to put it
another way, to what extent is UK manufacturing going
down the composites route? ‘You have to say to anyone
making aircraft parts not using composites -“beware”!’
comments Scaife. ‘The lead has been set by Boeing and
Airbus in terms of future aircraft programmes.’ And, he
believes, this will filter down to subcontractors ‘because
right the way through it’s about saving weight,
especially with fuel price increases. Singapore Airlines
have just downsized the cutlery for this reason! If you
can reduce weight you can also reduce the amount of
fuel you put in, so it’s a double weight saving.’
Designing for the application
It’s tempting for those of us who have worked in and
around metals for many years, and perhaps aren’t so
conversant with the technology of composites, to put
them all into one box labelled CFRP. Is there more to it?
‘Yes, there’s a whole battery of products,’ explains
Scaife; ‘different grades of carbon fibre and resins in
which they can be seated, and then there are different
fibre densities and weaves. It’s very much about
designing for the application. One of our potential
partners is talking about having 7,000 different product
lines, all with slightly different flavours of material
property.’
So, composite specification is driven by application;
but is processing also a factor? ‘This is the difference in
working with composites’ explains Richard Scaife. ‘The
design, material and processing all have to be
considered and reviewed jointly rather than using
standard features, more so than for metals. Also, the
material properties are affected by fibre orientation so
they are different in different directions. How you are
going to make the component is influenced by the
30 MWP november 2008
design in terms of getting the properties you want,
where you want them.’
Is this creating a new technology discipline? ‘It’s a
different way of looking at design. The key thing is the
move away from trying to replace a metallic component
directly. Designing for composites is a different thing
entirely, and I think that’s where you’ll see composites
coming into their own - where the design is for
composites, not just as a substitute for metal.’
What are the implications for repairing
aerostructures? ‘There are repair methods being
developed; the 787 wouldn’t be marketable otherwise -
over 50% by weight is composite, nearly everything
except engines and landing gear; and there are moves
on landing gear to generate hybrid structures which are
a mixture of metallic and composite.’
Such hybrids create additional problems for
machining operations - eg in drilling stacks - and
work is already being done at the AMRC on cutter
technology. ‘You are cutting very dissimilar materials
with very different cutting properties, and it is a long
term issue. Generally you need specialist tooling, but in
aerospace, as opposed to general engineering, that’s
often the way. But there’s great potential for companies
to get left behind. We have partner companies
developing tooling for composite work; they can see a
growing market and we are supporting them to develop
cutting equipment.’
One danger is that demand could exceed supply. Scaife
explains that there is a major scaling up of composite
manufacture worldwide to feed the aerospace market.
‘But we’re also looking at composites in offshore
applications - hybrid structures to reduce weight and
manufacturing costs. This may sound unusual but again
it’s all about designing around, and making best use of,
material properties. You see also the development of
wind energy, which is probably a bigger user of
composites than aerospace; the growth experienced
there puts significant demand on carbon fibre producers
so there is an element of catching up, in the same way
that the new aircraft programmes are sucking up a lot of
titanium, so there is a scaling up of titanium production.
So it’s probably harder to get hold of material, but it
shouldn’t be a deterrent because producers are increasing
their production.’ http://camtec.group.shef.ac.uk
Wheeling out the 787 - over 50% by weight is
composite, nearly everything except engines and
landing gear (and even that could move to hybrid
metal/composite structures)
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