Costs and Aircraft Applications of Thermoplastic Composites 143 7.2.5 Strut Fairings on the Boeing 757-200's Jet Engines[255] The four fairings used on the struts of the Boeing 757-200's jet engines (two per engine) are produced from injection-molded glass-filled PEEK.These parts approximately measure 51 cm by 30 cm in size and weigh 2.2 kg.They have to resist to hostile conditions including high levels of moisture,sonic vibrations and high air speeds.Despite daily exposure to these conditions,they must providc cfficicnt pcrformancc,givc long-tcrm durability and maintain an attractive appearance.PEEK resin was selected after evaluation of a variety of other thermoplastic materials including nylon 6/12.polyetherimide and polycarbonate.The PEEK fairings are about 30%lighter than fairings of conventional aluminum construction and they are 90%less expensive. 7.2.6 Aerosurface Components on Subsonic Missiles [256] McDonnell Douglas Astronautics Company is investigating the replacement of metallic and thermoset composite structures on subsonic missiles with thermoplastic composites.The components include metal fins and wings for the Harpoon and Tomahawk low speed missiles and the Tomahawk glass/epoxy air inlet duct and radome. Harpoon Missile Figure 61 shows the Harpoon control fin design concept.The skins are made with either continuous unidirectional tape or thermoplastic resin reinforced with woven cloth.The cloth or tape prepreg is laid-up and thermoformed.The laminate skins are placed in the mold, and the core material consisting of the same thermoplastic resin as the skin but reinforced with 30%chopped carbon fibre is injection molded forming the core. Both PPS and PEEK thermoplastic resins have been investigated for this application. Tests conducted on these materials have shown that PEEK is superior,but further cost analysis has to be performed before choosing the final material. Tomahawk Missile Figure 62a shows that the Tomahawk fin uses the same design concept as the Harpoon fin.The wings and fins,the air inlet duct,and the radome have all been redesigned with thermoplastics.The proposed wing redesign for optimum strength and stiffness is shown in Figure 62b.The two thermoformed laminate skins will be thermally welded to the core. The choice of the material to replace the hand lay-up glass/epoxy air inlet duct has not been made yet.PPS,PEEK and polycarbonate with various reinforcement combinations are candidate materials.The proposed molding process is complicated since it includes multi-shotCosts and Aircraft Applications of Thermoplastic Composites 143 7.2.5 Strut Fakings on the Boeing 757-200’s Jet Engines [255] The four fairings used on the struts of the Boeing 757-200’s jet engines (two per engine) are produced from injection-molded glass-filled PEEK. These parts approximately measure 5 1 cm by 30 cm in size and weigh 2.2 kg. They have to resist to hostile conditions including high levels of moisture, sonic vibrations and high air speeds. Despite daily exposure to these conditions, they must provide efficient performance, give long-term durability and maintain an attractive appearance. PEEK resin was selected after evaluation of a variety of other thermoplastic materials including nylon 6112, polyetherimide and polycarbonate. The PEEK fairings are about 30% lighter than fairings of conventional aluminum construction and they are 90% less expensive. 7.2.6 Aerosurface Components on Subsonic h&Ales [256] McDonnell Douglas Astronautics Company is investigating the replacement of metallic and thermoset composite structures on subsonic missiles with thermoplastic composites. The components include metal fins and wings for the Harpoon and Tomahawk low speed missiles and the Tomahawk glass/epoxy air inlet duct and radome. Harooon Missile Figure 61 shows the Harpoon control fin design concept. The skins are made with either continuous unidirectional tape or thermoplastic resin reinforced with woven cloth. The cloth or tape prepreg is laid-up and thermoformed. The laminate skins are placed in the mold, and the core material consisting of the same thermoplastic resin as the skin but reinforced with 30% chopped carbon fibre is injection molded forming the core. Both PPS and PEEK thermoplastic resins have been investigated for this application. Tests conducted on these materials have shown that PEEK is superior, but further cost analysis has to be performed before choosing the final material. Tomahawk Missile Figure 62a shows that the Tomahawk fin uses the same design concept as the Harpoon fin. The wings and fins, the air inlet duct, and the radome have all been redesigned with thermoplastics. The proposed wing redesign for optimum strength and stiffness is shown in Figure 62b. The two thermoformed laminate skins will be thermally welded to the core. The choice of the material to replace the hand lay-up glass/epoxy air inlet duct has not been made yet. PPS, PEEK and polycarbonate with various reinforcement combinations are candidate materials. The proposed molding process is complicated since it includes multi-shot