CompositesWorld
Issue link: https://cw.epubxp.com/i/576646
OCTOBER 2015 96 CompositesWorld PLANT TOUR we see it as the best way to achieve the compaction and consolida- tion pressure required, to drive out any volatiles," Ofringa notes. "And for an aerospace structure, that is critical." Good buckling, R&D; One of the frst parts we see on entering the Hoogeveen facility are the just-molded spars for the Gulfstream G650 rudder/elevator (Fig. 2, p. 95). Tey're fabricated in lengths of 4m and 6m at thicknesses of just less than 1 mm to several millimeters. Tey're consolidated in an autoclave and feature integrated ribs with regional thicknesses (from weldments). Te material is TenCate Cetex carbon fber/PPS. Tese parts, says Ofringa, are exemplary of the tough/not brittle attributes that make thermoplastics so appealing to aerospace fabricators and OEMs. Tey are designed, says Ofringa, to buckle slightly during service, without breaking or cracking. "A thermo- plastic rudder consists of thin skins welded onto a stif internal skeleton of ribs and spars. When the rudder is used, it is loaded in torsion and the skins are allowed to buckle at 70% of limit load (the load that occurs once in the lifetime of an aircraft). Tis allows for thinner skins than otherwise, resulting in a weight reduction as compared to conventional composites." Fokker's thermoplastic composite parts are tested and certifed at 1.5 times limit load. Much of what Fokker has learned about thermoplastic compos- ites fabrication, assembly and performance is fueled by the company's signifcant research and development (R&D;) work, which is guided by Ofringa. Fokker's R&D; lab employs 10 people and has equipment for environmental simulation, 3-D printing (provided by Leap Frog, Alphen aan den Rijn, Te Netherlands), Fig. 4 Wing leading edges awaiting welding Molded of glass fber/PPS, the Airbus A380 wing leading-edge skins on these racks soon will be integrated with ribs and spars via welding in Fokker's large Tool Jig Room. Fig. 5 Compression molding of rib components A380 wing leading-edge ribs are compression molded, using materials cut from TenCate's Cetex preconsolidated glass fber/PPS sheets, on this massive press supplied by automated machinery manufacturer Pinette Emidecau (Chalon Sur Saone, France). Fig. 6 "Meshing" leading edges ribs and skins Molded ribs for the A380 wing leading edge are bonded to the skins by means of resistance welding, in which a metal mesh strip coated with PPS is attached to the edge of the rib. A current is applied to the mesh, which softens the PPS and bonds the rib to the skin. The metal mesh becomes part of the bond.