The use of carbon fibre reinforced plastics are becoming increasingly popular in modern aircraft production, Airbus are looking to focus their attention to the “thermoplastic” CFRP material, which holds several key advantages over the more commonly used thermoset type, including its 100% recyclability.
CFRP materials, both thermoplastic and thermoset, are created when thousands of carbon filament threads are bundled together before being combined with a matrix to form a composite material. A ply or layer is made to the specified size and orientation, and then more layers are added until the piece has the necessary properties to support the loads it will carry. The resulting material is composed of approximately 60% fibres and 40% resin.
Thermoplastic CFRP has superb fatigue and damage tolerance properties, along with shorter manufacturing cycles and lower moisture absorption. It can even be welded, which cannot be done with thermoset-type CFRP.
According to Airbus researchers the key difference between thermoplastic and thermoset CFRP is what happens during their individual curing processes. When you put ‘raw’ thermoset material into an autoclave and ‘cook’ it, there’s a chemical reaction, the actual chemical composition of the material changes however with thermoplastic composites, you can melt a finished piece and reshape it and it still has the same chemical composition.
This difference makes thermoplastic composites very attractive. Why? Because Airbus and its suppliers produce literally hundreds of tonnes of scrap thermoplastic composites each year, With thermoset, you would need to burn the resin, and all you end up with are the fibres the remaining 40% of resin is lost. With thermoplastic composites, the scrap produces the same amount of recycled material, which could be used in a variety of structural and interior applications.
Thermoplastic-type composites also do not require curing in an autoclave and can be stored at ambient temperature without need of a freezer equating to significant reductions in energy costs. Thermoset composites have become more prevalent in the air transport sector over the years because it is perceived, sometimes incorrectly, to be cheaper.
There are many suppliers of thermoset, which drove down the cost, but now, there are more and more thermoplastic composites manufacturers entering the market, so prices are coming down. Still, even before the A350 XWB, Airbus had more than 1,500 reference parts made from thermoplastic composites and its use will continue to grow.