16 AEROSPACEMANUFACTURING | NOvEMbER 2009
scratching the surface
of green technologies
The green agenda continues to dominate aerospace developments both from
a regulatory perspective and from economic operating imperatives. CERAM’s
principal consultant for aerospace and defence, Dr Chris Pickles looks at the
applications of surface characterisation technology in low carbon developments.
T
he use of composite materials as a means of lower drag available from thinner wings are just two of the
‘lightweighting’ aircraft structures and components is a future developments that will maintain the inexorable demand
direct response to the need to reduce carbon footprint for surface characterisation as an essential component of
whilst at the same time achieve fuel economies. With all composite material development programmes.
airlines that land in Europe gearing up to be included in the Composite materials depend critically for their operational
European Emissions Trading Scheme (EU-ETS) from 2012 performance on the strength of the bond between the fibre
– and with a baseline reporting year of 2010 – improving and the matrix polymer, which must withstand wide ranging
performance efficiency has become a huge priority. New temperature and humidity conditions. Any disruption to
material developments hold the key to the successful this interface will affect the adhesion and can lead to resin-
achievement of green objectives whilst maintaining, or fibre disbondment. Similarly, coating adhesion to composite
improving, other essential product performance requirements, structures is dependent on both the physical and chemical
and surface characterisation techniques that continue to make a nature of the substrate and of the coating. Whilst the substrate
major contribution to these endeavours. surface roughness has an optimum value related to the keying
The picture is changing continuously, but a reasonable of the coating, in the aerospace industry the coating outer
estimate of the current use of carbon fibre in aerospace surface needs to be as smooth as possible to reduce drag. The
applications is in the region of 30,000 tonnes per annum. machining of composites is also an area of potential concern in
According to informed sources this will rise to 170,000 tonnes terms of fibre breakout and edge finish, whether the structure
per annum by 2020. Fuel represents over half of total airline is machined or waterjet cut.
operating costs and a 30% weight loss would deliver a 6% fuel
cost saving. Maintenance costs are also reduced significantly Composite surface analysis
by the use of composite structures. Other developments In all of these areas, surface characterisation techniques
also continue apace with thermoset resins coming under the are able to deliver quantitative and highly spatially resolved
influence of the REACH directive in terms of the need to chemical and physical information. The most common surface
phase out the curing agent MDA. Beyond this, the attraction characterisation techniques used for the testing of composite
of thermoplastic resins in terms of their recyclability and the materials include the analysis of the chemical composition
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