Continuous Composites has successfully completed a two-year Air Force Research Laboratory (AFRL) contract after additively manufacturing the structural carbon fibre spars of a Low Cost Attritable Aircraft (LCAA) wing assembly.
Completing the project through Lockheed Martin, Continuous Composites coupled commensurate materials with its Continuous Fiber 3D Printing (CF3D) technology to develop a ‘new structural design paradigm’ which reduced costs and lead times for attritable airframe structures.
The project leaned on a range of manufacturing technologies, including long fibre injection moulding for ribs, additive manufacturing to produce the tooling, automated fibre replacement for skins, autodrill and robotic assembly, as well as CF3D to print the spars. These spars were printed with CF3D at lengths of eight feet and weighed four pounds each. The in situ impregnation, consolidation and curing is said to have resulted in significant cost and time reductions, while the full automation of CF3D featured cutting and refeeding which enabled ply drops and variable part thicknesses to be applied within the structure.
Upon delivery to the AFRL, the 3D printed spars underwent static load testing and are said to have achieved a 160% design limit load before the compression skin buckled. There was no measured or visual damage to the printed spars, while they achieved a 60% fibre volume fraction with approximately 1-2% voids.
“The successful work with Continuous Composites and AFRL’s focus on CF3D for this project not only advances new 3D printing technology but also offers the potential for aerospace-grade composite printing in high-performance industries,” commented John Scarcello, Senior Manager at Lockheed Martin Skunk Works. “We recognise this process is paving the way for broader applications within both defence and commercial applications, and Lockheed Martin plans to be part of that future of advanced manufacturing.”
Continuous Composites has been working with Lockheed Martin and AFRL for a couple of years and, while continuing to develop its CF3D technology, has been collaborating with the likes of Siemens, Arkema, Comau and Güdel to enhance its carbon fibre additive manufacturing process. CF3D is based on a motion platform that is driven by tool path generation software, depositing snap cutting thermoset resin impregnated with continuous dry fibre. The technology is modular – with improvements to the end effector, materials compatibility and automation still being worked on – and is capable of producing high-quality composite parts with better strength to weight ratio than many metals. Speaking to TCT last year, the company’s CEO Tyler Alvarado noted how aerospace and defence would be a key market for Continuous Composites, and speaking on this announcement, he hints that there is more to come through its work with the US Air Force.
“This project is one application where CF3D showcases the significant cost reduction and design freedom while exceeding the stringent mechanical properties required for aerospace,” offered Alvarado. “Our team is very appreciative to Lockheed Martin, the US Air Force, and other partners for including CF3D in this LCAA project. We are taking the next steps to select our long-term DOD prime partner while engaging the Air Force as evidenced by the upcoming announcements of our key involvement with AFRL PiCARD programme in parallel to a five-year CRADA.”
“The success of this LCAA project shows great opportunity for additive manufacturing with customised CF3D material solutions that can orient structural fibres optimally. It is especially attractive to avoid expensive tooling in manufacturing aerospace structural parts,” added Ray Fisher, AFRL Programme Manager. “I look forward to additional opportunities to incorporate CF3D in increasingly complex structures that are further optimised for attritable enabling production.”
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