Shark Aero craft benefits from spread tow fiber composites

With a goal of building a 300-kg ultra light aircraft that can fly 300 km/h, Shark Aero turns to TeXtreme spread tow tapes to take the weight out of its newest plane.

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Oxeon AB (Borås, Sweden) reports that Slovakian ultra light aircraft (ULA) manufacturer Shark Aero has integrated Oxeon's spread tow fiber technology into composites used on its newest aircraft.

Shark Aero approached Oxeon in late 2008 when it began designing its first prototype ULA, with a view to reduce weight on its composites parts in order to build faster planes. Speed and weight are key aspects to be kept in mind for designing the aircraft as an important goal is to reach the dream top speed of 300 km/h for ULAs and to still keep the weight to a maximum of 300 kg/661 lb.

Besides keeping the ULA within the limited weight, the main reason for weight savings is that it enables a lot of improved flight features. A lighter plane will normally have quicker reactions; a craft that weighs less with identical aerodynamic configuration requires less power to fly and consequently will be more fuel efficient. When reducing weight, the payload is also improved, take-off- and landing distance is reduced and the climb rate tends to be better as well.

Oxeon's TeXtreme spread tow tapes are used to weave carbon fabrics with virtually no crimp to realize mechanical properties similar to a cross ply of UD. TeXtreme is based on combining two novel technologies: spread tow and tape weaving. First the carbon fiber tow is spread into thin flat spread tow tapes, and then these spread tow unidirectional (UD) tapes are used to weave a spread tow fabric.

A test program was initiated in which Shark evaluated different TeXtreme variants and tested the mechanical properties of the resulting composite parts. The test program, which concluded in early 2010, showed that the use of TeXtreme brought several mechanical and process advantages over the presently used materials in the industry. In particular, use of TeXtreme enabled composite parts to be redesigned to be significantly lighter without sacrificing essential strength properties. Further, the surface smoothness benefits of TeXtreme eliminated the need to use glass fabric as an outer layer.

Consequently, Shark Aero replaced its 200-gsm and 90-gsm fabrics with 160-gsm and 80-gsm TeXtreme fabrics respectively.

Vladimir Pekar, CEO of Shark Aero, says, “by changing to TeXtreme we saved an impressive 50 kg in total. On average the weight of smaller parts such as the stabilizer, elevator, rudder, spinner and landing gear doors, have been reduced by 60 percent. Weight savings of this magnitude are paramount in this category of aircraft as it allows us to build a faster airplane. Our aim is to use the best possible materials and TeXtreme qualifies for this.”

When producing Shark’s fuselage in series, it weighed 41 kg/90 lb, which is 25 kg/55 lb less than the 66kg/146 lb prototype produced using conventional fabrics. Pekar further adds, “As a consequence of switching to TeXtreme and after recalculating the whole Shark fuselage with FEM, a saving of 25 kg [55 lb] for the fuselage alone was very good as it was more than planned. With such weight savings from use of TeXtreme, Shark Aero could meet the specifications demanding maximum empty weight of 300 kg for a single-seat ULA directly and at the same time improve many crucial flight features.”