Material advances dictate AM’s future

Material advances dictate AM’s future
Material advances dictate AM’s future

While the use of metals in additive manufacturing has grown, a key requirement for the aerospace industry is for high temperature polymers and composites to be widely and economically available.

University of Exeter's CALM coordinator, James Bradbury reports. Additive manufacturing (AM) has captured the imagination, opening exciting new avenues. But despite its appeal, it remains a niche player in the aerospace market, with technical and commercial challenges limiting its widespread adoption.

Representatives came together at the University of Exeter to discuss the latest developments and what is needed to move this industry forward. An exclusive event, and the first on the topic in Europe, The European strategy for additive manufacturing for high temperature polymers was hosted by the University's Centre for Additive Layer Manufacturing (CALM). CALM was set up four years ago, with Airbus Group Innovations UK as a partner, to educate, the aerospace supply chain, through research and knowledge exchange workshops, about the capabilities offered by the technology, consequently helping increase adoption in aerospace and other sectors. Engaging closely with the AM supply chain, CALM has strengthened its expertise in polymers and processes for AM, particularly in high temperature polymers and composites.

The event was partnered by manufacturers and suppliers of laser sintering (LS) equipment EOS UK and Victrex, the main UK manufacturer of high temperature polymers for a range of processes. Joining the debate were businesses leading the world in developments in this area, including Airbus Group, GKN Aerospace and Thales Group.

Attendees discovered future options, with updates from the University of Exeter on new grades of materials, including PEEK, glass and carbon-based composites, and updates from Victrex about new PEEK materials. They also learnt about new LS systems from EOS, manufacturers of the EOSINT P 800 used by CALM (one of only eight in the world). Delegates also learnt about Airbus Group Innovation UK's use of carbon nanotubes in AM, collaborative research with South West Metal Finishing, which is developing techniques for improving surface finish of parts, and examples of high temperature polymers being used in novel applications, including Maplebird's insect scale aerial vehicles. This was supported by presentations and discussions about ongoing challenges and the steps required to take the industry to the next stage.

Focusing exclusively on polymer developments, the event offered a unique opportunity for attendees to confirm or modify strategic directions and development options.

Thales Group's research engineer, Romain Czarny said: “The event was an excellent opportunity for us to engage with some other major corporations throughout the supply chain. It was great to attend an event where people were discussing different materials to metals for a change, and which catered for the range of interests of the businesses involved. High temperature polymers, including PEEK are interesting to explore for aerospace applications because of their mechanical properties.”

<Benefits and applications>

With no tooling costs, short lead-times and minimum waste, AM's benefits for design optimisation are well recognised. The technology is ideal for manufacturing low volume items, tooling requirements, inspection fixtures and design checks (prototyping). Attendees discovered where these advantages are being realised and considered, with companies like Airbus Group revealing potential uses of AM with high temperature polymers.

Examples included using the technique to produce a demonstrator light mounting enclosure for a winglet, which needed to function within a wide temperature range of -50°C to 150°C. With relatively low volumes and further design changes possible, AM offered a clear opportunity.

Another application where AM's bespoke design options offered an advantage was for the ‘shimming' of gaps between components during assembly. Custom shims could be produced, based on measurements taken during component assembly. These shims would need a high working temperature, good compression properties, good chemical resistance and thermal stability. Unfortunately, current materials for AM do not have the properties required, but this example highlights the developments needed.

One objective of the event was to highlight challenges and discuss potential solutions, so clear strategies could be developed and future research could focus on the right areas. Key themes included: Size restriction: AM is limited by the size of the machines. For wider spread adoption, this is an issue that needs to be addressed; Cost: current materials for AM are costly compared to those of the same grade in injection moulding; Functional performance: despite advancements and ongoing developments, the functional performance of AM polymers lags behind equivalent injection moulding options, with reduced elongation, increased brittleness, and a poorer surface finish; Knowledge exchange and awareness: The use of AM for high temperature polymers and composite materials is in its infancy, so there is a lack of knowledge about its potential.

Critical to overcoming the above challenges is the development of new polymer and composite materials that aren't just replications of injection moulding grades, but specifically designed for AM. Work on this is already underway, with Victrex and the University of Exeter having developed alternative materials that are lightweight, fire retardant and strong. Development of new materials and technologies will dictate the future of AM for the aerospace industry.

Attendees said they recognised the advantage of the event, in bringing key players together to create a clear vision and direction.

Airbus Group Innovation UK's research engineer, Thiago Medeiros Araujo said: “It was a useful and informative event, with interesting presentations, and it was great to have the chance to discuss the issues we face, including the need to drive costs down. While we don't want to miss the opportunities presented by the technology, equally, we don't want to plough ahead with projects that don't fit well with our strategic objectives. This is why it is so important for us all to work together, to identify what the priorities are and how we might overcome any current limitations of the technology.”

<Train to gain>

Another major take-away from the event was the requirement for more training programmes, including appropriate university courses, and Continuing Professional Development (CPD). CALM is investigating this further and will publicise any future training and courses it can offer.

Oana Ghita, Lead Academic for CALM, said: “The event gave us the chance to understand better the industrial challenges, while presenting our research findings to a selected audience. Over the last couple of years, we've focused on material development, leading us also to research on powder morphology, flow and multi-functionality for tailored performance - a perfect match with the industrial needs.”

“The event was a great success, with a range of presentations from different sectors and excellent attendance by representatives from the entire supply chain,” concluded Bradbury. “We got a clear view of the challenges and the direction the industry is heading, so we can tailor our research accordingly. We are keen to ensure this is the first of many similar events in the future.”

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