Thermoplastics are quickly replacing metal parts

Aerospace applications are seeing a considerable rise in the innovative use of thermoplastics, as their strength and lightness makes them ideal for replacing metal parts.

One such example is a partnership to achieve valuable weight and cost savings within the quality and price-sensitive air transportation industry between SFS intec and TxV Aero Composites in the re-design of an aircraft storage-bin bracket. Originally made from aluminium, the new bracket will be made of Victrex AE 250 composites overmoulded with Victrex PEEK (polyetheretherketone) polymer. SFS is qualifying TxV’s hybrid overmoulded composite part for use in a commercial aircraft.

The weight, size, complex geometry and high load-bearing specifications of the overhead storage-bin bracket made the SFS part a suitable candidate for the pioneering hybrid overmoulding technique at TxV. Another consideration was the 60-70% scrap produced through several milling steps required for the original aerospace-grade aluminium bracket.

Sascha Costabel, head of innovation at SFS Intec GmbH Aircraft Components says: “Our decision to work with TxV is a strategic one. We are convinced that thermoplastic composite components will play an increasingly larger role in the manufacture of aircraft. It may well be that several different technologies will each have a role in the future of aircraft production. TxV’s hybrid overmoulding process, is a good option for components that must withstand high levels of mechanical stress and geometries that require multiple processing steps where conventional machining is used.”

The processing and performance advantages of PAEK thermoplastic composites, combined with state-of-the-art automated manufacturing, positions TxV to meet the industry’s cost and weight challenges. Finished composite parts, complete hybrid overmoulded components and assemblies are produced using continuous manufacturing processes with cycle times measured in minutes rather than the hours required by thermoset alternatives. These innovative products can deliver weight savings of up to 60% over conventional metallic solutions.

“This project represents an exciting commercial application of our overmoulded hybrid part technology,” comments Jonathan Sourkes, senior account manager at TxV. “SFS intec recognises the benefits of our approach to part manufacturing in terms of processing efficiencies and overall system cost savings. Scrap reduction, decreased weight, elimination of secondary processing and lower part count are all benefits of moving from metal to a hybrid overmoulded composite solution.”

Victrex AE 250 composites are based on the PAEK (polyaryletherketone) family of high-performance polymers and are specifically designed for lower-temperature processing. This enables a unique hybrid moulding process that combines the strength of continuously-reinforced thermoplastic composites with the design flexibility and proven performance of Victrex PEEK (polyetheretherketone) overmoulding polymers – in this case, Victrex PEEK 150CA30.

Commercial aircraft use thousands of brackets and system attachments from the cockpit to the tail of the plane. As a result, these components can account for significant cost and weight. The high-performance PAEK polymer-based components can be manufactured more efficiently than conventional thermoset alternatives and can deliver significant weight savings compared to aluminium, stainless steel and titanium while offering equivalent or better mechanical properties such as strength, stiffness, and fatigue. In the aircraft industry, of course, weight savings translate into lower fuel costs and increased productivity.

TxV Aero Composites came into being in early 2017 as a joint venture between Victrex, a leading supplier of PAEK and PEEK-based high-performance polymer solutions, and Tri-Mack Plastics Manufacturing Corporation. The objective was to accelerate the commercial adoption of polyketone-based composite applications throughout the aerospace industry, by leveraging the manufacture of parts utilising new and innovative processes. The US-based manufacturing facility is operational and production ready.

Stratasys, meanwhile, claims that carbon fibre 3D printing is very much in vogue in the manufacturing arena. Its engineering-grade thermoplastic carbon fibre is incredibly light but tough, giving unparalleled strength for dependable functional prototyping, end-use parts and rugged tooling, often replacing low-volume metal parts.

Those traits make it a popular choice for UAV components and tooling in aerospace, for example, as well as for bumpers, fixtures and brackets in automotive and transportation, in addition to sporting goods and general manufacturing aids.

The new Fortus 380mc Carbon Fibre edition is the culmination of 30 years of industry experience for Stratasys, which invented the Fused Deposition Modelling (FDM) technology employed by the machine back in 1989 and in doing so began a revolution.

Without the cost normally associated with a high-end printer, the Fortus 380 guarantees accurate, reliable, optimum-strength parts using ASA and FDM Nylon 12 Carbon Fiber, a material boasting the highest stiffness-to-weight ratio of any of our FDM options.

Part of the Fortus range, which is certified for producing end-use parts, it can create precise, repeatable models faster than ever before, utilising the high-performance thermoplastics used in traditional manufacturing processes.

But unlike some of its competitors, the Fortus 380mc Carbon Fibre edition can do exactly what it promises to, delivering results at a superior level. Its carbon fibre material contains 35% chopped carbon fibres, compared with the 15% figure of its nearest rival, and achieves 30 to 50% higher density on finished parts.

In terms of printing speed, the Fortus 380 is four to five times faster than anything else out there using carbon fibre – but that does not come at the expense of quality. An easily soluble support system allows users to create more complex geometries, with the support material adhering to the build tray. It’s a far more reliable method than gluing parts to the bed, which can lead to peeling and movement.

All production parts need to be built in the controlled environment that a heated build chamber provides – a feature that comes as standard with the Fortus 380, but not with other machines. Failure to control the build environment results in uncontrollable shrinkage rates, meaning an end part cannot be validated for use.

Author
Engineering Materials

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