Cabin crew, doors to plastic please

An A350 XWB demonstrated at the Dubai Air Show 2015

In this feature for Plastics News Europe, James Snodgrass looks at how Airbus is saving weight by using PEEK polymer for the cabin doors of its A350-900.

In recent years all industries have seen a push to reduce weight and aerospace is more the rule than the exception.

The market for widebodied aircraft, that can ply 300-plus passengers across oceans, has been a two-horse race for nearly 20 years, since Airbus’s arch-rival, Boeing, swallowed up McDonnell Douglas. But while Airbus had the A330 and A340 to compete with Boeing’s 767 and 777 single-decker aircraft, it had nothing to compete with Boeing’s “jumbo” 747.

It addressed this, in the last decade, with the launch of the A380 “superjumbo”, the largest passenger jet ever made. With composite construction, the A380 could carry more people than a 747, with less fuel burned.

Boeing, however, didn’t seem to be trembling. Its spokespeople said that there was no market for “superjumbos” and that, increasingly, people were travelling direct routes rather than, so-called, hub-and-spoke routes.

In the meantime, Boeing was working on its – also largely composite – replacement for the 767, the 787 Dreamliner, designed to work those direct routes. To date 1,124 787s have been ordered and 340 delivered to customers. In comparison, there have been 317 A380 orders and 173 deliveries (with speculation that many of the backlog orders will never be built).

Airbus tried to fight back with an A350 based on the A330 but with modified aerodynamics and engines. This didn’t please the airlines and the project was relaunced as the A350 XWB (extra wide body). Designed for direct routes, and with variants targeted at Boeing’s 787 and 777, the A350 XWB has proved to be more successful, with total orders of (ironically) 787 units, with 10 deliveries to date.

With composite wings and composite fuselage frames, the A350-900 variant will typically seat 314 passengers yet weighs just 115.7 tons (compared with the A330-300 which can seat 295 but weighs 124.5 tons). While large structural components make the greatest saving, every little bit helps.

In 2012 we reported on how PEEK polymer had been selected for the cargo drainage pipe system, the first non-metal plumbing in any civilian aircraft. Now it has been revealed that PEEK has been used for a structural component in a civilian aircraft for the first time.

Carbon fibre-reinforced PEEK 90HMF40 from UK-based materials firm Victrex has been used to replace aluminium in a fitting for the aircraft door of the A350-900. The piece, injection moulded by Airbus Helicopters in Donauworth, Germany, has received regulatory approval and has entered serial production.

By substituting metal with plastic, the brackets are 40% lighter and 40% less expensive to produce. The fibre-reinforced polymer (FRP) structure of the A350 XWB’s aircraft door uses an outer skin coupled with a bracing structure on the inside. The bracket manufactured from Victrex PEEK 90HMF40 thermoplastic connects the outer skin to points on the internal bracing structure. The two components form a box-type structure to exploit the maximum geometrical moment of inertia.

The PEEK 90HMF40 material was specified by Airbus. It needed a material that could easily withstand the moisture that accumulates inside aircraft doors. Aluminium needs a special surface coating to prevent corrosion.

Christian Wolf, head of airplane doors research and technology at Airbus Helicopters said: “The suitable material, supplied by Victrex, as well as their expertise and collaboration with their materials experts, have contributed to the successful development and component qualification. The expertise gained from the initial use of fibre-reinforced PEEK can be transferred to other components and to other areas of application with similar requirements.”

The new material has been developed from Victrex’s 90-Series PEEK materials, which are primarily used in very thin-walled injection moulded components. Victrex claims that 90HMF40 has up to 100 times longer fatigue life and up to 20% greater specific strength and stiffness than aluminium 7075-T6 under the same conditions.