Strutting the stuff

Ed Hill discovers more.
The perpetual demand to find materials with greater strength to weight ratios for use in aerospace applications is leading to advances in the production of parts that until now would have been beyond the realms of composites.

Exelis Aerostructures is now marketing a new line of composite struts, tubes, and rods under the Exelis STaR brand. The top-tier US global aerospace and defence manufacturer has licensed the technology originally developed by Belgium composite specialist Bodair. The European company developed a patented filament winding process which produces lightweight tubular parts that can have various end fittings incorporated into the tube as an integral part of the manufacturing.

Although composite parts have been developed before for these applications, Bodair's process allows for even greater weight savings and more flexible production.

“The unique aspect about this technology is the ability to make a single piece design that is even lighter than equivalent composite parts,” explains Mike Blair, vice-president and general manager of Exelis Aerostructures. “Changing from an aluminium or stainless steel rod to a composite one normally produces a weight saving of around 20-30%. Our STaR parts reduce weight by 5-10% more. The filament winding process means our parts are lighter than segmented designs or designs made by resin transfer methods.”

It's a wind up

Bodair uses pre-impregnated carbon fibre filament winding technology which it says allows maximum control of the process and guarantees porosity levels that are significantly lower than RTM. It also gives improved repeatability and consistency in product quality.

Exelis has invested in new Lean technology, equipment and clean room facilities at its plant in Salt Lake City, Utah that will be able to produce around 40,000 parts per year using the new method.

“We were connected to Bodair through a mutual customer. They liked the technology and felt a company of the size and experience of Exelis in producing production composite parts for the large airframers would create a good match for increasing production. We also have the quality certifications and quality systems in place with the OEMs that take a while to achieve, so we were able to offer those assets in the partnership.”

Exelis expects to produce components such as floor beam and wing box struts, control rods and torque tubes.
“There is huge potential in supplying system rods for control surfaces or even parts such as connecting rods for luggage bins in the cabin. There are thousands of these types of tubular components on an airplane.”

One advantage of the Bodair system is its ability to produce new or reverse engineered parts relatively rapidly.

“A great benefit of this technology is the speed with which you can design and produce a part. For example, we were sent some drawings from a customer and within three weeks we were able to deliver a production quality part. To produce a similar quality part in that time frame using other composite manufacturing methods would not have been possible.”

Exelis' investment in its STaR products is already paying dividends. In July the company was awarded a multimillion dollar contract to supply Airbus with composite floor beam struts for the A380 until 2023. The struts connect the passenger cabin floor to the aircraft fuselage. Deliveries for the new components are due to start in 2015.

Exelis Aerostructures' involvement in civil aircraft programmes has grown significantly in the last 12 months. The company has also been awarded a contract to supply structural frames for the Boeing 787-9 and -10 after being awarded processer certification from the OEM in six specifications (BAC5578 and BAC5317-1 through to -5).

“The fact that we did these qualifications in less than a year is something that we are very proud of and it has allowed us to be put on the approved supplier list. It opens up many more possibilities for us.

“There is a mind-set in the aerospace industry of continuous improvement so by definition you have to keep meeting the new higher standards that are set and that is consistent with our own culture. We want to compete in an operationally excellent environment and we structure our facilities and our team around that philosophy as it gives us a competitive advantage,” Blair adds.

Exelis has added a further 140,000ft² of manufacturing space to accommodate the 787 work and is in the process of making the first prototypes.

“Our process qualification from Boeing has all been part of an aspiration to make more composite components for them. The capacity and experience we offer was attractive to Boeing and this contract is significant proof that we can invest in this market and go out and capture the work.”

Exelis also continues to supply composite tanks to many of the major civil aerospace programmes and some military applications, as well as composite parts for GE engines. And it is seeking to promote its latest composite manufacturing capabilities to other major aerospace OEMs and engine manufacturers.

Striking a balance

Blair says the group aims to keep a balance between its civil aerospace work and defence contracts. On the military side it is involved in providing structural components for the F-35 fighter and the tail rotor pylon and sponsons for the new Sikorsky CH-53K heavy-lift helicopter, the C-17 military transport and JASSM missile.

“The newer military programmes provide a valuable amount of work that is due to ramp-up in the near future and complements what we are doing on the commercial side.”

Exelis' investment in rod/strut manufacturing is a further example of its pragmatic approach to additional expansion in the composites aerostructures market.

“We are very confident about this technology for many aerospace applications, particularly system rods and struts. Many of these parts are currently metallic so we see a huge untapped market for composite alternatives.

“This process enables us to be competitive when it comes to producing rods and offers the lighter weight desired. From both a cost perspective and weight perspective we believe this will transform the industry when it comes to these sorts of components,” Blair concludes.

www.exelisinc.com/business/aerostructures