What do aeroplanes, bridges, and wind turbines have in common? They can all be made from lightweight, strong, composite materials made of polymers reinforced with strong carbon fibres.
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.