Airbus, Fokker seek less expensive fiber metal laminate and lightweight aluminium layers

Airbus and Fokker Technologies are partnering for research on automated production of fiber metal laminate (FML), lightweight layers of aluminium and glass fiber. Early FML, also called Glare, was used on the upper fuselage and the vertical stabilizer of the Airbus A380. Automated production and next-generation fiber will improve FML performance and reduce cost.

Maarten van Mourik, Fokker director for large commercial aircraft, says FML has better material properties than aluminium, especially in fatigue resistance, allowing for lighter designs. “FML also offers considerable weight advantages versus polymer composites in smaller fuselages because these composites carry a weight penalty, due to minimum thickness for damage tolerance.” While fatigue resistance is FML’s chief advantage, it also has superior behavior against corrosion, lightning strikes and fire penetration.

Mourik says FML’s better fatigue resistance means inspection intervals are shorter than for aluminium, but FML can be repaired much like aluminium. The material is best suited for fuselages, bottom wing skins and, because of better impact properties, leading edges of wing and horizontal or vertical stabilizers.

The present layup process of FML is labor intensive, compared with aluminium. But FML is formed in a mold tool, so there is no need for stretching, rolling or mechanical or chemical milling. Compared with polymer composites, FML is less expensive as it is half aluminium and requires less autoclave time and simpler layup.

Today’s manual layup process for FML alternates layers of prepreg glass fiber and aluminium. Local reinforcements can be made inside the laminate or externally with a separate doubler package, for example around a door or window cut-out. Airbus and Fokker are now aiming for “significant cost reduction by automation and reduced manufacturing and material cost,” Mourik explains. The partners’ research will take FML automation to Technology Readiness Level 6.

Mourik says it is still too early to specify the exact research responsibilities of Airbus and Fokker, but his company will have 25 employees involved in the project.