Fibre-reinforced polymer composites have many useful properties, but their big drawback is they are typically complex and expensive to manufacture. In recent years, three-dimensional (3D) printing of composites has been successfully demonstrated using thermoplastic polymers and discontinuous fillers, but the resulting 3D-printed composites often have poor mechanical properties and low service temperature due to the limitations of the constituent properties. Consequently, 3D printing of composites using continuous carbon fibres and thermosetting polymers is expected to offer exceptional mechanical properties and thermal stability as well as featured design flexibility, low cost, reliability, and repeatability. However, no additive manufacturing technique has ever been reported to process continuous carbon fibres and thermosetting polymers for direct 3D printing of the finished composite.

Now, a team of engineers from the University of Delaware has developed a 3D printing technology that enables low-cost, flexible production of items made of fibre-reinforced polymer composites using continuous carbon fibres and thermosetting polymers. Their results were recently published in the journal Matter.

This is believed to be the first time anyone has achieved such 3D printing of continuous carbon fibre and thermosetting composite

Continuous carbon fibres and thermosetting resins are very important to make strong and lightweight composites, and they are widely used in many applications, such as aerospace, automotive, and sports products,” said Kun (Kelvin) Fu, “3D printing could reduce labour and tooling cost, and fabricate composite in a more energy-efficient, rapid, and reliable way with minimum defects.

The team developed an approach called localised in-plane thermal assisted (LITA) 3D printing, which allows the user to control the thickness and degree of curing of liquid polymer that solidifies into the desired shape.

In LITA 3D printing, the researchers carefully manipulate the temperature of the carbon fibers, aiding the flow of liquid polymers into channels between the carbon fibers. Then, the polymers are cured, solidifying into a three-dimensional structure. No post-curing is needed in LITA 3D printing, which could save a large amount of energy compared to the conventionally fabricated composites requiring tens of hours of post-curing.

The team developed a robotic system that includes a unique printing head and automated robot arm. This customized 3D printer allows the group to print a variety of shapes and structures.

LITA 3D printing could provide many industries with a rapid, energy-efficient method to make composite components in a variety of shapes using a variety of combinations of polymers and fibers.

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The bike’s unibody frame is made by 3D-printing one single continuous piece of carbon-fibre thermoplastic, which the company says is stronger than any traditional carbon fibre frame on the market today. The use of thermoplastic materials not only make the bikes stronger and more impact resistant but also lightweight with the Superstrata Terra weighing in at just 1.27 kgs while the e-bike Ion version weighs 10.98 kgs, depending on size.

While 3D printing can be a more costly process, Superstrata says it makes for a more bespoke design and will appeal to people willing to pay extra for a custom fit. Customers can send in their measurements, and Superstrata will 3D-print the bike down to the spokes. Each frame takes about 10 hours to create, and the company claims it can create up to 250,000 unique combinations.

The bikes are available for pre-order on Indegogo and are scheduled to ship in Q1 and Q2 of 2021 with special early bird pricing starting at $1,299 for the Terra and $1,799 for the Ion.

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Key to the strength and versatility of these hybrid, layered materials in high-performance applications is the orientation of fibres in each layer. Recent innovations in additive manufacturing (3D printing) have made it possible to finetune this factor, thanks to the ability to include within the CAD file discrete printer-head orientation instructions for each layer of the component being printed, thereby optimising strength, flexibility, and durability for specific uses of the part. These 3D-printing tool-paths (a series of coordinated locations a tool will follow) in CAD file instructions are therefore a valuable trade secret for the manufacturers. 

However, a team of researchers from NYU Tandon School of Engineering led by Nikhil Gupta, a professor in the Department of Mechanical and Aerospace Engineering showed that these tool-paths are also easy to reproduce — and therefore steal — with machine learning (ML) tools applied to the microstructures of the part obtained by a CT scan. 

Their research, Reverse engineering of additive manufactured composite part by toolpath reconstruction using imaging and machine learning, published in Composites Science and Technology, demonstrates this method of reverse engineering of a 3D-printed glass-fibre reinforced polymer filament that, when 3D-printed, has a dimensional accuracy within one-third of 1% of the original part.

The investigators, including NYU Tandon graduate students Kaushik Yanamandra, Guan Lin Chen, Xianbo Xu, and Gary Mac show that the printing direction used during the 3D-printing process can be captured from the printed part’s fibre orientation via micro-CT scan image. However, since the fibre direction is difficult to discern with the naked eye, the team used ML algorithms trained over thousands of micro CT scan images to predict the fibre orientation on any fibre-reinforced 3D-printed model. The team validated its ML algorithm results on cylinder- and square-shaped models finding less than 0.5° error.

Gupta said the study raises concerns for the security of intellectual property in 3D-printed composite parts, where significant effort is invested in development but modern ML methods can make it easy to replicate them at low cost and in a short time. 

Machine learning methods are being used in the design of complex parts but, as the study shows, they can be a double-edged sword, making reverse engineering also easier. The security concerns should also be a consideration during the design process and unclonable toolpaths should be developed in future research.

Nikhil Gupta, Professor in the Department of Mechanical and Aerospace Engineering

The study is supported by the National Science Foundation grant from the Secure and Trustworthy Computing program. 

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BMW first started the additive manufacturing of prototype parts back in 1991, for concept vehicles. By 2010, plastic-and metal-based processes were being rolled out, initially in smaller series, to produce items such as the additively manufactured water pump wheel in the DTM race cars. Further series production applications followed from 2012 on, with a range of components for the Rolls-Royce Phantom, BMW i8 Roadster (2017) and MINI John Cooper Works GP (2020), which contains no less than four 3D-printed components as standard.

Last year, the company produced about 300,000 parts by additive manufacturing. The Additive Manufacturing Campus currently employs up to 80 associates and operates about 50 industrial systems that work with metals and plastics. Another 50 systems are in operation at production sites around the world.

Access to the latest technologies is gained through long-standing partnerships with manufacturers and universities, and by successfully scouting for industry newcomers. Back in 2016, BMW i Ventures invested in the Silicon Valley-based company Carbon, whose Digital Light Synthesis technology achieved a breakthrough in planar processes, using a planar light projector to enable super-fast component production.

Further investments were made in 2017, when the company became involved with Desktop Metal, a start-up specialising in additive manufacturing of metal components and developing innovative, highly productive manufacturing procedures. Close collaborations with Desktop Metal continue. In the same year, BMW i Ventures invested in the US start-up Xometry, a platform for on-demand manufacturing.

The latest investment was in the German start-up ELISE, which allows engineers to produce component DNA containing all the technical requirements for the part, from load requirements and manufacturing restrictions to costs and potential optimisation parameters. ELISE then uses this DNA, along with established development tools, to automatically generate optimum components.

The pre-development unit of the Additive Manufacturing Campus optimises new technologies and materials for comprehensive use across the company. The main focus is on automating process chains that have previously required large amounts of manual work, to make 3D printing more economical and viable for use on an industrial scale over the longer term.

The Additive Manufacturing Campus is also making a contribution to series production of plastic parts. In the POLYLINE project, the focus is on aspects such as digitally linking process steps, and the development of a consistent quality assurance methodology for the entire process chain. The Additive Manufacturing Campus will provide the backdrop for the project’s consortium of 15 partners to develop and test a future-proof, fully linked, automated production line for plastic components. Findings from the project are expected to help reduce manufacturing costs by as much as 50 percent, making a vital contribution to series production. In addition, integrated quality assurance methods will increase the stability of technologies and make manufacturing more sustainable.

Along with component manufacturing, the team at the Campus provides personal consultations and training courses for BMW facilities around the world that all manufacture 3D-printing components already, be it for prototypes or production, or as country-specific parts for customers.

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Taller turbines can increase renewable energy production while lowering the cost of energy and optimising construction costs. The partners will produce a wind turbine prototype with a printed pedestal, and a production-ready printer and materials range to scale up production. The first prototype, a 10-meter high tower pedestal, was successfully printed in October 2019 in Copenhagen.

GE Renewable Energy will provide design, manufacture and commercialisation for the wind turbines, COBOD will focus on the robotics automation and 3D printing and LafargeHolcim will design the tailor-made concrete material, its processing and application.

Concrete 3D printing is a very promising technology for us, as its incredible design flexibility expands the realm of construction possibilities. Being both a user and promoter of clean energy, we are delighted to be putting our material and design expertise to work in this project.

Traditionally built in steel or precast concrete, wind turbine towers have typically been limited to a height of under 100 metres, as the width of the base cannot exceed the 4.5-meter diameter that can be transported by road, without excessive additional costs. Printing a variable height base directly on-site with 3D-printed concrete technology will enable the construction of towers up to 150 to 200 meters tall. Typically, a 5 MW turbine at 80 metres generates, yearly, 15.1 GWh. In comparison, the same turbine at 160 meters would generate 20.2 GWh, or more than 33% extra power.

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Self-sensing is the ability of a material to sense its own condition which means you don’t need an implanted or attached sensor system reducing costs while increasing durability and sensor coverage.

Polymer-matrix composites, containing continuous carbon fibre, are known materials that have self-sensing capabilities based on measurable changes in electrical resistance of the continuous fibres. For example, a self-sensing composite was used for damage detection in a cylinder made by filament winding. The practical importance of such products can potentially be found in structural health monitoring in aeroplanes or critical parts of constructions like bridges.

Brightlands Materials Center is combining the self-sensing properties of continuous fibre reinforced thermoplastics with fabrication by additive manufacturing. Additive manufacturing with continuous fibres enables very precise positioning and orientation of carbon fibres. The carbon fibres are placed at chosen locations inside the product that forms an integral part of the structure. That means that the carbon fibre “sensors” are located where they are needed, and multiple fibres could form a range of sensors throughout the part.

The concept was proven by Brightlands Materials Center by monitoring deformation in a simple bending beam and in a scale model of a pedestrian composite bridge. Both were printed with an Anisoprint A4 Composer which allows full freedom of the carbon fibre layout and material choice. This is specifically important for sensing because carbon fibre has to stick out of the part to be able to make connections to the monitoring electronic hardware.

Damage detection by self-sensing in 3D printed bike frame lugs is part of the “100% Limburg Bike” project in which the centre collaborates with amongst others Eurocarbon, CeraCarbon, Brightlands Chemelot Campus and Belgian Cycling Factory – known from racing bike brands like Ridley and Eddy Merkcx – and which is supported by the European Fund for Regional Development and the Province of Limburg in the OPZuid framework.

Self-sensing can also play a role in the design and prototype phase of new products or in replacing spare parts that are not available anymore. 3D printed self-sensing fibre reinforced thermoplastics can help to gather information about the real use circumstances. During a testing period, the self-sensing 3D printed part registers the real dynamics and forces that a product needs to withstand. This gives designers and engineers a clearer understanding of what requirements the 3D printed parts will have to meet. As a diagnosis tool, 3D printed self-sensing orthoses or protheses might guide patients and provide valuable information to doctors, regarding stress distribution and movement patterns.

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More than twenty 3D printers are working day and night. Hundreds of visors have already been produced and dispatched to hospitals close to the Airbus facilities in Spain. Airbus leverages a patented design to manufacture the visor frames, using PLA plastics. 

Overnight, we have gone from making aerospace concepts to medical equipment. This genuinely makes a difference in the fight against the pandemic and I couldn’t be prouder of our teams working day and night on this Airbus project.

Alvaro Jara, Head of Airbus Protospace, in Getafe, Madrid

Despite the pause of the majority of production at Airbus’ sites in Spain following the Royal Decree of 29 March, Airbus employees are allowed on site to continue with this essential activity. 

In addition, Airbus in Germany also joined the project. The Airbus Protospace Germany and the Airbus Composite Technology Centre (CTC) in Stade, together with the 3D-printing network named “Mobility goes Additive,” are now supporting this project in Spain, also coordinating the collection and transport of visors to the Madrid region. 

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Master’s student Leo Baumann, in collaboration with the ETH spin-off 9T Labs, investigated the possibility to 3D print lightweight and selectively compliant composite structures. With the supervision of the doctoral students Dominic Keidel and Urban Fasel, the team developed a wing with a continuous skin and a morphing structure, which has highly adaptive and aerodynamically efficient control surfaces reducing the aerodynamic drag.

To proof the structural performance of the morphing wing, and to analyse the flight characteristics of the aircraft, the team developed a morphing composite drone. To achieve the desired trade-off between stiffness and compliance, they used a 3D printer developed by 9T Labs, which enables the manufacturing of parts consisting of both plastics and carbon composites. All structural components of the drone were created using 3D printing technology, with the exception of the wing skin and electronics. The manufacturing process and the flight tests can be found in the Journal of “Manufacturing Letters”.

The advantage of the 3D printed manufacturing methods is that the carbon fibres can be aligned to achieve the desired characteristics of the part. By aligning the fibres with the load paths, the properties of the material are optimally exploited. By printing complex geometries with less waste material, the parts could be manufactured at a lower cost compared to conventional manufacturing methods. The printing process is repeatable and easily adaptable, which allows multiple iterations of a part and fast fabrication of spare components.

The drone was manufactured in individual components, with the main structural parts of the wing, fuselage and V-​Tail being printed on the 3D printer. The lattice structure of the wing was then covered with a thin skin. This combination of a load-​carrying internal structure and the aerodynamically smooth surface leads to an efficient, lightweight aircraft. Both the plastics and composite parts are based on thermoplastic materials, which enables the reheating and welding of the structure. This could be used to assembly the final structure without requiring any additional adhesive.

Both the wing and the V-​Tail relies on the same morphing concept to achieve control around the pitch, roll, and yaw axes. The control surfaces on the wing are actuated by eight servo motors, which enable a maximum trailing edge deflection of 48mm. By individually controlling the deflection of each motor, the lift along the span can be varied, reducing the structural loads and potentially increasing the efficiency of the drone.

A three-minute maiden flight showed ample control of the aircraft through morphing. Not only the main wing, but also the V-​tail performed excellently, achieving full control around the roll, pitch, and yaw axis. Different manoeuvres, including barrel rolls and loopings, could be flown, showcasing the versatility of the aircraft.

9TLabs has recently closed a seed financing round of $ 4.3 million to finish the development of their industrial 3D printing solution and scale-up the first mass manufacturing industrial use cases.

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The authority is involved in developing the next generation of magnetic confinement reactor called a tokamak at their site in Culham, Oxfordshire. Research is focussed on preparing for the international tokamak experiment at the International Thermonuclear Experimental Reactor (ITER) in Saint-Paul-lès-Durance in southern France and for the following machine that will demonstrate the generation of power from fusion.

Fusion occurs when two types of hydrogen atoms, tritium and deuterium, collide at enormously high speeds to create helium and release a high energy neutron. Once released, the neutron interacts with a much cooler breeder blanket to absorb the energy.

The breeder blanket must capture the energy of the neutrons to generate power, but also prevent the neutrons escaping and ‘breed’ more tritium through reactions with lithium contained in the blanket. Each blanket module typically measures ~1 x 1.5m and currently weighs up to 4.6 tonnes.

Engineers are proposing to make use of high-performance ceramic composite materials and to form a unitised 3D woven structure with additive manufacture components. The cooling tubes in the breeder blanket would be integrated into the material and 3D printed parts used to define features such as connectors and manifolds.

To achieve a lightweight, temperature resistant structure, a silicon carbide composite material was chosen for the breeder blanket, with the internal flow channels being created by forming the composite around a disposable core.

With a CAD model produced, a weave design was then created for the composite. The structure needed holes robust enough to include tubes and needed to maintain the preform shape without distortion. They then produced a 3D woven structure on the loom with pockets for the 3D-printed tubes which could be formed into a rigid component.

The next step for the AMRC project is to continue the silicon carbide composite development and build a demonstrator that can be tested inside a reactor test facility in order to understand how it performs and reacts to the environment

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Using the Lulzbot HS1.2 printer he shows how to make this unusually shaped skateboard and puts it to the test at a local skatepark.

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