Composite brackets for life-of-aircraft service
Aircraft design and assembly is all about the sometimes competing goals of reducing weight and ensuring flight safety. Northern Ireland-based injection molding specialist Denroy Plastics Ltd. (Bangor, County Down, UK) is meeting both directives with a polyetheretherketone (PEEK)-based composite.
Airframer Bombardier (Montreal, QC, Canada) asked Denroy to replace small- to medium-sized machined aluminum and titanium brackets for wings, center wingbox and fuel-tank applications, intended to last the life of the aircraft despite constant immersion in fuel. Denroy, in close collaboration with its client and Victrex (W. Conshohocken, PA, US), selected the latter’s electrostatically dissipative polymer, trademarked VICTREX PEEK-ESD, which complies with lightning strike requirements, and is resistant to wear and aggressive aerospace fluids. Victrex also formulated the polymer for Denroy using proprietary fillers, which do not break down under shear when passing through the injection gate during the molding process. Thus, parts could be produced under optimum molding conditions without affecting the polymer’s electrostatic discharge properties.
The molded brackets, now specified in Bombardier’s C-Series, Global and Learjet aircraft, weigh 40% less than the metal versions, says Denroy sales/marketing manager Jim Knowles. In addition, manufacturing cost savings were achieved via part consolidation, integration of complex shapes, elimination of secondary machining/painting, and a reduction in scrap rate and cycle time.
Tim Herr, Victrex aerospace strategic business unit director, says Denroy has new polyaryletherketone (PAEK)/ PEEK hybrid molding process for loaded brackets. Read CW’s coverage of that hybrid process online here or click on “Overmolding expands PEEK’s range in composites” under "Editor's Picks" at top right.
Applications aren't as demanding as airframe composites, but requirements are still exacting — passenger safety is key.
Capable of volume production, thermoplastic composites will gain new market share in the aerospace industry.
The composite wing leading edge on Boeing’s Dreamliner features an integrated heating element that incorporates a sprayed metal conductive layer within the laminate stack.