Aerospace leads composite innovation

Fokker Aerostructures and its partners Ticona, Ten Cate and KVE Composites Group picked up the JEC 2010 aeronautics category innovation award for their use of carbon fibre reinforced Fortron polyphenylene sulphide (PPS) for the welded 4m long rudder and 6m long continuous fibre reinforced laminate structure elevators for the Gulfstream G650 executive jet aircraft.

Gulfstream says that it already has 200 orders for the new plane and sells an average of 70-80 planes annually. The use of composites is said to have eliminated hundreds of rivets from the manufacturing process, replacing them with induction welding.

The rudder and elevator constructions use carbon fibre reinforced polyetherimide (PEI) honeycomb composite trailing edges and a large number of press-formed carbon/PEI ribs with a thin outer carbon/epoxide Nomex skin.

The “post-buckled” multi-rib design of the new thermoplastic rudder control panels for the Gulfstream G650 save 10% in weight over previous epoxy composite sandwich panel versions, as well as being 20% less expensive to produce. According to Fokker Aerostructures, such thermoplastic composite primary structure parts are 50% lighter than aluminium or light alloy equivalents.

This application marks a continuing trend towards lower cost thermoplastic “physical processing” solutions and away from both thermosetting resin “chemically processed” composites and aluminium, Fokker Aerospace’s R&D director Arnt Offringa says, at least in smaller aircraft.

In a JEC forum presentation on induction welded thermoplastic control surfaces, Offringa described the next step as Thermoplastic Affordable Primary Aircraft Structures (TAPAS), which involves the use of unidirectional (UD) carbon fibre PEKK tapes in new design concepts and processes. The company hopes to have a technique using high speed ultrasonic fibre placement to automate CFRP carbon fuselage shell and torsion box components in production in 2011.

Another award for aviation industry automation went to EADS Deutschland and its partner SGL Kümpers and Airbus Operations for their highly automated preform production line for CFRP aircraft frames. This new BRAF “braided frame” process lowers manufacturing cost through reduced manual operations and is carried out using a circular machine sized to the same diameter as the aircraft’s fuselage.

BRAF combines braiding, winding and UD tape application and has been in use since the end of 2009 in the EADS Innovation Works R&D and technology centre in the northern German town of Stade.

SGL Kümpers says BRAF “enables maximum design flexibility and unmatched repeatability to meet the high-volume demands of future aircraft manufacture”. It says BRAF is under evaluation for production of aircraft such as the A350 XWB and future Airbus jetliners.

EADS was also recognised by the judges in the process category of the awards, this time for work with its partner the Belgian aerospace company SABCA Société Anonyme Belge de Constructions Aéronautiques. The team have been working under a European Framework programme project to develop MOJO - a means for structural adhesive bonding of aircraft composites claimed to cut assembly costs by up to 60%.

A full-size MOJO closed beam structure demonstrator was on show at the fair produced from upper and lower parts made with non-crimp carbon fabrics and tailored pre-formed profiles in out of autoclave resin transfer moulding (RTM) and vacuum-assisted resin infusion (VARI) processes.

According to the judges, projects such as MOJO are showing that structural bonding can provide an alternative to riveted construction in the CFRP industry. “This will lead to cost and performance benefits, along with improved damage tolerance characteristics,” they say.

Automation was also the subject of a briefing by Claude Chouet, sales manager at robotic and handling equipment supplier Matrasur Composites. A relatively high level of automation is used in the automotive and aerospace industries, Chouet said, but other sectors “are at a very poor industrialisation level.”

Chouet said there is practically no limit to use of robotics in composites production, giving an example of daily production of eight glass fibre reinforced plastic (GRP) pools, where the use of robots for chopped fibre, gelcoat, and release agent spraying can be combined with automatic colour changing and a carousel production flow management system.

Where non-industrialised equipment cost for swimming pool production is lower, at €50,000 against an industrialised equivalent at €1.2m, the corresponding annual labour costs are respectively €1.95m and €690,000. Chouet said that with an amortisation of less than three years, the industrialised version is a clear winner even before taking into account the €30,000 a year energy cost saving.

Aside from higher degrees of automation and productivity, JEC 2010 also presented an opportunity to see new innovative material developments, some of which addressed ecological and environmental issues. Armacell Benelux, for example, presented a new foam core material made of PET recycled from bottles.

Meanwhile, composites producer Gurit has started up production of extruded PET foam cores (G-PET). The product was launched in the first quarter of 2010 and G-PET production capacity is scheduled to be introduced in Gurit plants in China in the third quarter 2010.

Econcore showed a new hexagonal honeycomb core material made in polylactic acid (PLA). The company’s sales and marketing manager François de Bie says that skin layers are added after the core is produced in a second step using its continuous ThermHex production process and can be made from unfilled PLA material to produce a mono-material panel. It is also possible to use a flax fibre reinforced PLA.

A completely different core structure was presented by French start-up company PlastiCell. It is taking flat sheets of Victrex Aptiv film and laser welding them together along node lines to form a HOBE (Honeycomb Before Expansion) compressed block. The honeycomb structure is then water jet cut before being expanded to form the hexagonal core structure, followed by heat-setting at above the PEEK glass transition temperature (Tg) to stabilise the shape.

The JEC wind energy category innovation award went to La Tôlerie Plastique (LPT) for a flax fabric reinforced PLA windmill blade. These windmill blades are made by the “sheet composite” workshop processes of CNC machining and fabrication. The small wind turbine for which the blade has been designed can be easily installed on public and private buildings.

Composite core material developments of a more conventional nature came from the Danish company Diab. These included the Divinycell Matrix 7-7 structural core for boat decks and other applications. Said to be the lightest commercial foam core to meet the major deck classification requirements, the company says the product also has potential for wind turbine blades and nacelles.

Rudder control panels for the new Gulfstream G650 executive jet