Optimal surfacing for aircraft parts made of composite materials

Aircraft parts made of composite materials require optimal surfacing

As airplanes are increasingly made of composite materials, resorting to the best surfacing products for smoothness and lightning protection is necessary now more than ever. Solvay provides the leading surfacing adhesive just for that.

There are two reasons why airplane parts made of composite materials need a surfacing film applied onto them: for smoothness, because the surface of carbon fiber prepregs is always slightly irregular, and for protection against lightning strikes. Whereas metal parts can take lightning without much damage (airplanes get struck by lightning at least once a year on average), with composites, the damage could be very serious, which is why they need a conductive surfacing film to disperse all that electric energy.

Industry-leading surfacing for smooth composites

Surface Master™ 905 (SM 905) is the main resin used in Solvay’s adhesive surfacing film, and by extension, the name of the product. “We invented this industry-leading product from scratch about fifteen years ago [specifically Dalip Kohli, who is now head of Adhesives R&I, was its creator - at Cytec at the time, which is now a part of the Solvay group], and today we are the market leader in this segment,” says Scott Brown, Product Manager at Solvay’s Composite Materials Business Unit.

The concept of surfacing has been around for as long as composite materials themselves, as it’s a necessary step for both looks and aerodynamics. But the market has grown considerably within the last decade, in no small part thanks to the launch of the two first large aircraft predominantly made of composites, namely the Airbus A350 and the Boeing B787. These two alone have strongly driven sales for SM 905, says Scott.

Painting planes made easy

As mentioned, obtaining perfectly smooth surfaces is one of the main reasons aircraft manufacturers need a product such as SM 905; and in addition to perfecting the aerodynamics of the plane, it also makes painting much easier. “SM 905's unique chemistry cures with a very smooth surface that is much quicker to paint over,” explains Scott. “Our customers save a lot of time thanks to this.”

Certain parts such as engine nacelles have been made of composites for thirty years, but today, larger and more visible surfaces are concerned; simultaneously, customer standards in terms of esthetics have gone up, the motifs and logos painted on planes have gotten more sophisticated, and planes get bought, sold and leased more frequently than they used to, and the paint needs to be changed every time. “All these factors have contributed to increasing the sales of surfacing film over the last 10 or 15 years,” says Scott.

Lightning protection included

Similarly, lightning protection for composite parts has been around for over two decades. But Solvay has innovated by including that functionality in its surfacing film: SM 905 can come with a thin copper mesh for customers who want lightning protection on top of surface smoothness. “Thanks to this product, we’ve helped our customers automate their manufacturing processes,” says Scott. “They are able to apply SM 905 with integrated lightning strike protection using the same methods as they use to lay-up the underlying composite material, and then cure the structure all at once. The result is a part with a smooth finish and shorter cycle times in their factories." And that’s how Solvay helps manufacturers make ever lighter and safer airplanes…