At its Grottaglie site in Italy, Leonardo’s Aerostructures Division recently tested its FFF (Fused Filament Fabrication) additive technology in the production process for composite aerospace materials.
The test was carried out by replacing traditional metallic moulds with polymer-based elements (Carbon PA and Carbon PEEK), reducing the cost and time factors involved in the test process and offering an increase in design flexibility. By optimising the parameters of the Roboze beltless 3D printer in the test phase, Leonardo was also able to remove any porosity and surface wrinkles typically associated with items printed using fused filament fabrication technology – an essential factor also for maintaining a vacuum during the ‘curing’ stage of the process.
The beltless system – developed and patented by Roboze, an Italian company specialising in the design of 3D printing solutions – replaces the printer belts with a mechanical cogwheel movement that can guarantee a level of precision as fine as 0.01 millimetres.
“Techno-polymers such as Polyether Ether ketone (PEEK), combined with a high presence of short carbon fibres, open up some interesting horizons for development,” says Stefano Corvaglia, Intellectual Property Manager and Head of Research and Development of the Aerostructures Division. “What’s more, thanks to a technology that enables us to achieve previously unattainable levels of precision in fabrication, we can improve our capacity and speed in developing prototypes. Thermoplastic techno-polymers are polymers made up of non-interconnected chains that are linear or have few branches; by raising the temperature we’re able to bring them to a viscous state and therefore to shape them and, in the case of additive technology, to fabricate them in layers.
“Testing with these materials is of particular scientific and technological interest,” Corvaglia adds, “since they give some structural and chemical-physical properties of extreme technological significance to the items produced, for example thermal and chemical resistance.”
An important aspect of using techno-polymers for additive manufacturing is the ability to use them for high-temperature applications. Thanks to the high level of thermal stability given by the polymers and carbon fibres, no significant deformation occurs in the moulds. Their durability with the repetition of the thermal cycles is now also being studied.
To summarise, the flexibility that additive technology – through the use of the techno-polymers that can resist the pressures and temperatures of composite curing cycles (the process of cross-linking the polymer chains in the composite matrix (CFRP)) – represents a fundamental “game changer” in the aerospace industry, delivering reduced costs and development times.
This is not the only success for Leonardo in the field of additive manufacturing. In February, the additive manufacturing project led the Leonardo Aerostructures Division, represented by R&D Lead Engineer, Nicola Gallo, and in partnership with Roboze, was awarded the 2020 A&T Premio Innovazione 4.0 in the Research and Universities category. Automation and Testing (A&T) is the annual exhibition dedicated to Industry 4.0, allowing large Italian industrial companies, SMEs and start-ups to come together to share their latest developments.