With a continual need to improve efficiencies and productivity, innovative commercial airlines are revisiting traditional metal use in both secondary and primary structural components.
PEEK, a high-performance polymer, is in the metal replacement spotlight with its ability to support complex design needs, perform in very harsh or extreme operating conditions and provide cost efficiencies.
Airbus Helicopters is one such innovator, having successfully substituted an aluminium fitting within the door on the Airbus A350 with a primary structural bracket made from carbon fibre reinforced VICTREX™ PEEK. The result of this metal replacement? An up to 40 percent reduction in weight and production costs, and a much more eco-friendly use of raw materials!
So how did they design these costs out?
Revisiting material selection
Aluminium was the traditional material of choice for a bracket fitting within the Airbus A350 doors. The fibre- reinforced polymer structure of the A350 XWB’s aircraft door uses an outer skin coupled with a bracing structure on the inside, with the bracket connecting the outer skin to points on the internal bracing structure. This point-type joint reduces the deformation on the outer skin, maintaining the aerodynamic quality of the aircraft door. Also if a component near the bracket fails, the fitting will provide an alternative path for transferring structural loads.
One material, multiple benefits
Victrex’s team of material scientists and aerospace experts worked together with Airbus, to help with the successful design, development and qualification of VICTREX™ PEEK 90HMF40 polymer, a high modulus, carbon fibre-reinforced high-performance thermoplastic. Replacing the aluminium part with the injection- moulded polymer solution enabled Airbus Helicopters to realise several benefits:
- Up to 40 per cent reduction in weight
- Up to 40 per cent reduction in part costs – with savings across handling, processing and assembly
- Facilitating part assembly - joining the PEEK component to a thermoset carbon composite makes drilling easier as a tool change to metal drillers is no longer required
- Improved performance - the high-modulus PEEK polymer provides up to 100 times longer fatigue life and up to 20 per cent higher specific strength and stiffness when compared to aluminium 7075- T6 under the same conditions
- Up to 85 % better buy-to- fly ratio vs. aluminium - significantly reducing material waste by optimal use of raw materials in the injection moulding process
So, what does this mean for the future?
The thermoplastic qualified by Airbus is a high-flow, easy-processing material that allows to produce parts with a high modulus. This enables engineers to design components that have equivalent strength and stiffness to traditional aerospace metals such as stainless steel, titanium and aluminium, with up to 70 percent less weight.
Component engineers with design-to- build authority now have additional options in materials and manufacturing technology when reviewing the use of metal in other aircraft components, and thus can take advantage of performance and efficiency improvements offered by fibre-reinforced PEEK and the injection moulding process. This opens the door to an exciting new era in structural component design with integrated functionality and state-of- the-art manufacturing technology.
What is more, there are additional potentials achievable with the new solutions and technologies. The VICTREX AE™250 composites, we are pioneering with partners today, directly come to my mind along with the special, so-called hybrid moulding process. Applications made with this composite technology and process are being adopted as metal and thermoset replacements due to the increased demand for better performance, higher mechanical properties and cost reductions. Look forward to see them flying high and far soon.
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