The aerospace sector has justifiably held its head high as the pioneer in lightweighting. The use of exotic and highly-engineered ‘iums’ has led to huge game-changing advances in structural design, and now, with greater use of carbon fibre-reinforced composite structures, the technology continues to surge forwards.
But what about aircraft interiors? In their continual quest for our business, the airlines expend huge sums of money to give us the ‘biggest business class seat’ or ‘biggest IFE package’ or ‘most legroom’, creating a huge cabin make-over industry. If you board an aircraft which hasn’t had a cabin facelift for a few years, you notice it, and maybe next time you will fly with another operator. It wasn’t that long ago that the only film in the main cabin was on a couple of screens hanging down from the ceiling, and if your seat had a poor view, well tough! Now, if your personal screen isn’t 11” or so, with 20 or 30 personal viewing or listening options, you feel let down.
Coupled with this, a primary or secondary structure will last the lifetime of an aircraft (25 + years), whereas interiors will be replaced maybe six times in that period - and flooring probably even more. Hence end of life solutions are becoming incredibly important
Much of the composites used in interiors are still based on thermoset resin systems, and the clue really is in the name; once set, they’re set, and the ability to recycle or re-use is extremely limited. Many of these resin systems are still based on phenol (which has its own environmental impact concerns), to enable them to meet the stringent fire, smoke and toxicity (FST) demands we appreciate in these enclosed environments. With skill and enough energy, thermosets can be effectively chopped up and mixed in with other resins to mould things like car body trim parts. Re-use of these materials is a very valuable industry, pioneering in so many ways. But the reality is that tons and tons of it every year end up in landfill, or possibly worse. Is this consistent with the sector’s ‘leading from the front’ reputation?
Thermoplastics, on the other hand, offer real 100% recyclable options even with fibres embedded in them. Heat the resin back up to its melting temperature, and it melts again, and can be remoulded into another part. The right thermoplastic resins are incredibly chemically resistant and inherently give superb FST performance. Moisture absorbency into interior structures is a significant issue inside an aircraft; thermoplastic composite laminates are as close to non-hygroscopic as it gets, so that problem is greatly alleviated. And of course, when it comes to counting the cost of manufacture of parts, consolidation cycles for thermoplastic resins are measured in single-digit minutes, unlike the hour or more needed to cure thermosets. Oh, and the surface finish out of the mould is fantastic, obviating much of the fill, sand and sweep needed on thermosets.
Material costs are always important and polymer resin costs vary considerably depending on the performance required. Understanding the options available to today’s designers and manufacturers is key; designing with thermoplastics from the outset can significantly reduce part cost. If that is done, then the message on caring for the environment from the aerospace sector will be even clearer. Leading from the front in minimising environmental impact on our children’s and grandchildren’s worlds. That has my vote.