Composites are the latest battleground and Airbus is employing clever, but risky tactics. Two weeks ago, we reported how Boeing had attacked what it claimed were Airbus suggestions that Boeing’s reliance on composite material in the 787 had implications for safety. This week, Airbus has hit back, saying it was first to use composites in primary structures in the 1980s, and that its comments on its rival’s use of synthetic materials in the Dreamliner’s main fuselage were based on “operational” not safety considerations.
All this is a bit rich given that one reason Airbus limited composites mainly to the wing on the A350 was not the practicality of synthetic fuselages, but the cost of re-tooling to build them. There is every chance the European manufacturer will opt for a composite fuselage for its next-generation airliner to replace the A320 family around the end of the decade.
Although Boeing may yet surprise everyone by switching back to largely traditional materials for the 737 successor, Airbus will this time start with a clean sheet of paper. The manufacturing process improvements possible with monolithic composite structures could be compelling. Last week, EADS co-chief executive Noel Forgeard said Airbus would be investing heavily in composite technology over the next few years and that designing lighter aircraft at a lower cost was the key challenge facing aircraft manufacturers.
Arguing over composites is, of course, nothing new. Manufacturers of metal aircraft have been dismissing synthetic construction for years. They did have some ammunition – early glassfibre aircraft were built using essentially boat moulding techniques, while “black aluminium” carbonfibre aeroplanes were expensive to produce, and not much lighter than metal ones – the raw material was dearer than aluminium and wastage was high.
Industry has learned to use the right material in the right place. Carbonfibre has advantages – high stiffness-to-weight and fatigue resistance – and better resin matrices have improved damage tolerance. The downside is that damage is usually invisible (delaminations or voids). But if there is damage, cracks do not spread as with aluminium.
The key to using any material is to understand it thoroughly and to develop “design allowables”. This means that, even if damage is present (such as cracks that form between inspections in metal airframes, or delamination caused by someone dropping a hammer in composites), it cannot develop in a way that would catastrophically weaken the structure before the next inspection. And that means understanding how the material ages over 20 to 40 years of service – knowledge that is only now available in large enough quantities to meaningfully guide designers.
Airbus has more experience of this than anyone. The National Transportation Safety Board report on the 2001 American Airlines A300-600 tail separation noted the carbonfibre fin’s immense strength, and was impressed by its damage resistance and design margins. Airbus knows Boeing is not taking a design risk by making more than half of the 787 from composites. But it knows airlines are wary of composite fuselages and wings – not because they do not trust them, but because they are worried they will not be able to repair them themselves, or they will be pricey to maintain. That was a lesson they learned, painfully, when early composites were introduced for things like flight controls and engine nacelles.
Airbus is exploiting that fear in the battle with the 787 – in the same way it plays the four engines versus two in the A340 vs 777 contest.
There is no question that designing an all-composite fuselage and wing is a challenge for Boeing – look at the saga of Raytheon’s Premier I and Hawker 4000. It is not easy to get design and development right. But once it is right, there is nothing intrinsically riskier about composites than aluminium.
Airbus is biding its time. If it gets its strategy right, it could leapfrog its rival in terms of technology while leaving Boeing to bear the pain of persuading airlines that plastic airliners are a good thing.
Source: Flight International