High-Performance Composites

NOV 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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Page 51 of 67

5 0 | H I G H - P E R F O R M A N C E C O M P O S I T E S INSIDE MANUFACTURING 5 0 | H I G H - P E R F O R M A N C E C O M P O S I T E S INSIDE MANUFACTURING at -18°C/0°F until time for delivery to the customer. (Occasionally a customer will specify dry preform layups, and apply resin during construction of the part. In this case, as the dry fbers are spread, they are bonded onto a polyester scrim that holds the fbers together and sub- sequently supports the laminate be- tween plies.) When the prepreg preforms arrived at Decision's facility, they were layed up into the molds for the airframe parts — the fuselage, tail and wing sections, in- cluding the wingbox — fabricated by De- cision in its Ecublens facility. The epoxy flm ensured a better bond to the honey- comb core in the wingbox. The principal structural element of the wing, the 27m wing spar, was particularly complex: a rectangular box made of four fat plates, each a structural sandwich construction cored with Dupont (Rich- mond, Va.) Nomex honeycomb. The spar box features bulkheads to reinforce left and right/inner and outer wing spar pan- els — all constructed from NTPT's pre- forms. Its central portion features fac- eskins of TPT preforms comprising four plies of 100-g/m 2 tape in ±45° orienta- tion. The left and right ends of the spars, however, are solid laminates rather than sandwich constructions, made from TPT preforms consisting of four plies of light- er, thinner 25-g/m 2 tape in ±45° orienta- tion. This specifed fber architecture ful- flls the torque resistance and bending stiffness requirements, which were the main design criteria for the spar box. Decision vacuum bagged the parts and cured them out of the autoclave at 80°C/176°F in a 30m/98-ft long, 4.5m/14.8-ft high oven that is built into the Ecublens factory along the length of one wall. The oven is accessible by means of a sliding door that can be tightly sealed during the cure cycle. After cure of the individual parts, the spar boxes and bulkhead assemblies were bonded together at the joints using prepreg technology from Cytec Indus- tries (Woodland Park, N.J.). The prepreg was used as a doubler at the joints. Each wing section was postcured before fnal assembly with mechanical lug fasteners. Then, Decision installed 17,000 solar panels over the cured com- posite skin across the entire wingspan, the fuselage and even the horizontal and vertical stabilizers. The solar panels con- vert the sun's radiant energy to electric- ity that powers the aircraft's four electric motors. During daylight hours the solar cells also recharge the lithium batter- ies that permit powered fight at night, using electrolytes invented by Solvay (Brussels, Belgium). The result? An extraordinarily light- weight fying machine that, despite a battery package that weighs 633 kg/2,077 lb and a 72m/236-ft wingspan (as wide or wider than the world's most massive conventional and military transport air- craft), weighs a mere 2,300 kg/5,071 lb. The future of your Carbon Fiber production begins with Harper. Whether the goal is R&D samples or high volume production, let our experts design the ideal system to meet their business and technical objectives. No one else ofers a full range of Carbon Fiber process lines to support the scale-up of your operation: harperintl.com • Scientifc Lines • Pilot Lines • Microlines™ • Production Lines Despite a battery package that weighs 633 kg/2,077 lb, the Solar Impulse 2 has an extraordinarily low empty weight of 2,300 kg/5,071 lb.

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