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97 Advanced Engineering | Show report for manufacture, and makes it 20% less expensive than Invar moulds.” The idea to combine Invar-36 with carbon fibre came from the company’s knowledge that both are suitable for use in tools for manufacturing carbon composite parts, but moulds made from the former are costly and heavy, while those made from the latter are less durable and thus have shorter lifespans. “The result is a mould with the low cost, light weight and short lead times of carbon fibre moulds, and the strength and lifespan of Invar-36 moulds,” Birtles noted. “So when UAS designers want to produce composite materials for new airframes – particularly for testing new wings and fuselages – they can be manufactured more quickly and less expensively than with Invar tooling.” UAVE displayed its Prion Mk3 UAV to showcase the value of composite materials in unmanned aircraft. “When you’re designing a UAV, minimising weight is everything, and composites form a big part of that,” said Grahame Grover. “We use carbon fibre and fibreglass to make the airframe, which gives us a naked weight of 28 kg on our 3 m long, 3.8 m wingspan UAV. The fibreglass forms the main outer skin, while the main internal structures, tailplane and central wing struts are carbon fibre.” The Prion Mk3 was originally developed to replace manned aircraft in survey and surveillance applications. More recently, the aircraft have been successfully sold to scientists for Arctic and Antarctic research into atmospheric monitoring, topographic studies and penguin population censuses. “We find the composites respond very well to the conditions of these colder environments, even if such missions do still require spending a lot of time looking at the UAV’s avionics and other systems. All the equipment needs to be rated down to suitable operating temperatures,” added Grover. “Power comes from a bespoke 120 cc single-cylinder, four-stroke fuel- injected engine, which consumes 0.5 litres of unleaded fuel per hour of flight, at a cruising speed of 80 kph.” Deployable payloads include EO cameras, digital recording PCIMCA memory cards, data transmission relays, caesium vapour magnetometers and additional smaller systems. Anglo-Krempel displayed its capabilities in building UAV structural parts from composite materials. “Our carbon fibre tubes are produced using a convolute-winding process,” explained Craig Wintle. “We take the prepreg materials and wrap them onto a mandrel as it turns, then cure the materials and break the resulting tube off the mandrel. “The mandrel is a simple shaft shape that is easy to reproduce, keeping tooling costs and thus manufacturing costs low for end-users such as UAV manufacturers.” The company also has thousands of mandrels of differing sizes, to cater for a wide range of UAS types, Wintle added. Anglo-Krempel also produces a range of hybrid structures, such as sandwich panels of honeycomb aluminium skinned with composites. It said these allow it to address manufacturing challenges such as balancing thermal behaviours and shrinkage rates of metals with those of composites. “Bonding infrastructures can vary greatly, so you need to understand the necessary bond strength to determine the kind of filament, adhesive or mechanical bond necessary,” Wintle said. Unmanned Systems Technology | February/March 2019 An example of Ascent Aerospace’s HyVarC carbon composite UAVE’s Prion Mk 3 has a carbon fibre and fibreglass airframe