High-Performance Composites

MAY 2014

High-Performance Composites is read by qualified composites industry professionals in the fields of continuous carbon fiber and other high-performance composites as well as the associated end-markets of aerospace, military, and automotive.

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M A Y 2 0 1 4 | 5 9 the fore and aft gussets — they add stiff- ness and supplementary paths for land- ing gear loads — while the wing spars must ft inside the spar box ends. A 3-D fabric, woven from T700 carbon fber sup- plied by Toray Industries, was chosen to handle the structure's high interlaminar shear loads. Supplied in the form of a sock-like preform by Highland Indus- tries, a subsidiary of technical textile source Takata (Tokyo, Japan), it enables quick lay up of 10 plies over an expand- able mandrel. Notably, VX Aero has replaced the sandwich construction of the original craft, which featured extensive use of foam and honeycomb core, with mono- lithic skins reinforced by post-bonded hat stiffeners to reduce weight and en- hance manufacturability. The canopy cut- out is now bolstered by a CFRP rail that Skillen integrated into the glare shield as a one-piece structure. Thus, a reliably consistent fuselage/canopy interface is achieved with minimal parts and as- sembly. "The canopies will ft easily into the fuselage opening every time and be interchangeable with each other in the feld," Skillen explains. Once the wingbox assembly is com- plete, fxed inner cockpit panels will be attached to the forward and aft seat beams and then the rail/glare shield will be affxed, followed by the cabin foor and frewall, which separates the en- gine from the cabin. Finally, the fuselage halves will be bonded using a fxture de- signed to account even for the glue thick- ness tolerances. After the frewall and fuselage are bonded, the aircraft's engine, still con- nected to its wheeled stand, is bolted to the frewall. Because the Falcon fuselage will only weigh 70 lb/154 kg, the assem- bly can be wheeled around the produc- tion foor easily, eliminating the need for a crane. The wingbox assembly is all CFRP: 3-D woven material in the spar box and 3K plain weave in the other components. Like the original, the new Falcon will use glass fber prepreg in the fuselage. Glass reinforcement is suffcient because the fuselage loads are smaller than those in the wing, and glass reinforcement will enable the radio transmissivity of inter- nal antennae. Prepreg layup, rather than what would be a complex infusion setup, was chosen for the fuselage, based on manufactur- ability and consistency/repeatability. Prepregged C-PLY will be used in the wing spars, wing skins and horizontal tail. Most of the other small parts will be infused, but some will be made using wet layup. Each material and process has been chosen with the balance between part performance and manufacturing ef- fciency in mind. Fast Falcon retooled After 18 months of computer modeling every component on the airplane, CAD fles were fed to VX Aero's 3-axis CNC VX-1 KittyHawk C-PLY airframe laminates Layup for the VX-1 KittyHawk top and bottom skins used +45°/0° and -45°/0° C-PLY (left), alternating in a six-layer stack (12 plies per six layers), with a 150-g/m 2 weight and 0.006-inch thickness per two-ply layer. Parts were then infused (photo on right) with the same high- temperature epoxy used to infuse the tooling. load transfer and a lack of hard points for structural connections. The construc- tion scheme needed improvement, and it would be necessary to optimize the de- sign for manufacturability. "Quality and effciency had to be designed into every assembly and process," he says, "to con- trol costs and cycle time in an actual pro- duction environment." In pursuit of those goals, VX Aero is employing the concept of 'self-rigging subassemblies' in the Falcon's design. For example, the heart of the airframe is a carbon fber-reinforced plastic (CFRP) spar box. As the anchor component of the wingbox assembly (see top of p. 57), its outer mold line (OML) surfaces align with and locate those of the next higher assembly. This helps to minimize the cost and complexity of assembly fxtures yet hold tight tolerances. The new wingbox assembly also ad- dresses an issue in the original aircraft. Namely, landing gear loads were directly imparted to the fuselage with no load path carry-through from one side to the other. And because the large fuselage cutout for the polycarbonate cockpit can- opy is located directly above the region that absorbs gear loads, this structural confguration resulted in unacceptable defection. To compensate, VX Aero re- designed the forward and aft seat beams as key elements of the wingbox assem- bly. They are now attached through the wing roots to the spar box, which now provides the primary load path for the wing moments. Materials and assembly The spar box is a continuous box beam with 0.1-inch/2.5-mm thick walls. Both its A and B (inner and outer) sides are critical dimensions. The outside locates Source: VX Aerospace Source: VX Aerospace 0514HPC IM PlantTour-OK.indd 59 4/22/2014 3:59:14 PM

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