CompositesWorld
Issue link: https://cw.epubxp.com/i/866813
SEPTEMBER 2017 86 CompositesWorld INSIDE MANUFACTURING Interest in FMLs is growing again as aeroengineers search for light- weight solutions adaptable to new narrowbody commercial aircraft. ยป ere is no doubt that composites have earned their way into aerospace structure, as evidenced by e Boeing Co.'s (Chicago, IL, US) and Airbus' (Toulouse, France) leap to composite wing and fuselage structures in the 787 and the A350 XWB, respectively. But recent questions about whether those same composites could be practical replacements for the thin aluminum fuselage skins found on aging narrowbody, single-aisle aircraft, such as Boeing's 737 and the Airbus A320, have helped revive interest in already certified hybrid materials called fiber-metal laminates (FMLs) that combine metal and composite products and are designed to take advantage of the best qualities of each material class. Genesis in fatigue performance Riveted aluminum aircraft structures are vulnerable to fatigue cracking. FMLs were the result of a long investigation into ways to improve aluminum fatigue performance by bonding multiple thin layers of the metal with polymer adhesives. "Our company began developing metal bonded structures, consisting of thin aluminum sheets hot-bonded together, from the early 1950s, a technique that helped reduce weight and crack growth in aircraft," says Maarten van Mourik, director of programs at GKN Aerospace's (Redditch, UK) Fokker business (Papendrecht, e Netherlands). e transition to a metal/composite hybrid, however, came about 30 years later, during work done by Fokker in coopera- tion with researchers at Delft University of Technology (TU Delft, Delft, e Netherlands). "To further increase fatigue performance, in the early 1980s, our technologists started investigating the addition of fibers to the adhesive bond lines." e Fokker/TU Delft collaboration led to the concept of fiber-metal laminates (FMLs) as a distinct class of hybrid composites for aircraft structure. After the demise of the original Fokker Aircraft company in 1996, focused research continued at TU Delft, in close coop- eration with Alcoa (New York City, NY, US), Dutch chemical company Akzo (now AkzoNobel, Amsterdam, e Netherlands) Fiber-metal laminates in the spotlight By Sara Black / Senior Editor Early aerospace composite material makes a comeback These fiber metal laminates combine aluminum with fiberglass prepreg, offering many advantages for fuselage structure. The GKN Aerospace Fokker business makes the panels in Papendrecht, The Netherlands. Source (all image) | Fokker business of GKN Aerospace