Smac Aero, a Toulon, France-based company specializing in elastomers for soundproofing and vibration dampening, is here at the Paris Air Show (Hall 2B Stand C140-158) exhibiting Smacpreg, a combination of pre-impregnated (prepreg) carbon fibers with a layer of rubber. As CEO Philippe Robert emphasized during a visit to the company’s development and production facilities, the new product is suited to fiber placement robots. It is easy to cure along with the basic composite material, he added.
A similar product, Smacwrap, consists of a very thin ribbon (0.1- to 0.2-mm thick) of rubber designed, too, for easy utilization by a fiber placement machine. That material is sold without prepreg. Even a very small amount of Smacwrap viscoelastic material is claimed to bring effective dampening on a composite structure, when it is located strategically in the structure’s core.
Smacwrap and Smacpreg have no aerospace application yet, but Robert had arguable reasons to sound optimistic. First, he has sold Smacwrap samples to some airframers. Second, these two products are said to be five times lighter than Smacsonic. Used on Dassault Falcon business jets, Smacsonic is a thin plate of aluminum or carbon, covered with a layer of Smactane viscoelastic rubber. A double-sided adhesive can stick it to the interior of a fuselage. The principle is to dissipate, between the fuselage and the plate, the vibrations caused by fuselage flexural modes. Smacsonic weighs between 0.51 and 0.61 lb/sq ft.
In addition to Falcons, it has also embarked on the Boeing 787 and the Airbus A350XWB. “Boeing was already using this kind of concept but this is the first time we have signed a deal with the U.S. manufacturer; we supply Smacsonic for half of the 787’s fuselage,” Robert explained. On the A350XWB, Smacsonic will be used on doors–about 160 sq ft per aircraft.
Smacpreg, Smacsonic and its other products are examples of how active–relative to its size–Smac is in research and development. While it has only 42 employees, three engineers create several elastomer formulas per month. The research-and-development laboratory has just been expanded from 1,600 to 4,300 sq ft; with the additional equipment, this represents a €200,000 ($260,000) investment, Robert said.
Smac has been working, as part of a joint research project with Snecma, on the Leap engine’s fan blade. One layer of elastomer is applied on to the composite blade. Engineers are thus trying to repel the onset of flutter.
Smac’s recipes are secret–as opposed to patented. Obviously, not all of them will find applications. But one single successful formula can be the basis for 10 final products. Natural rubber is the most resistant. Meanwhile, synthetic ones can be better, for example, as for the range of temperatures they withstand.