Jan 19, 2016 | By Benedict

3D printing with multiple extruders and materials is a relatively new phenomenon within the 3D printing world. Makers and manufacturers are now able to create single 3D prints containing several materials, a development which has opened up a world of 3D printing possibilities. Now, a team of engineers from the University of Bristol, United Kingdom, has gone one step further down the combined materials road, by developed a novel method for 3D printing composite materials.

In this unique 3D printing process, ultrasonic waves are used to position millions of tiny reinforcement fibers, which are formed into a microscopic reinforcement framework, giving the material significant strength. This microstructure is then set in place with a focused laser beam, which cures the epoxy resin.

“The breakthrough was based on the simple idea of printing using a liquid polymer mixed with millions of tiny fibers,” explained Tom Llewellyn-Jones, the PhD student who developed the system. “This makes a readily printable material that can, for example, be pushed through a tiny nozzle into the desired location. The final object can then be printed layer by layer, as with many other 3D printing processes.”

The biggest challenge for the engineers was finding a way to manipulate the tiny fibers into the correct patterns, in order for them to provide the superior strength generally offered by composite materials. In the end, they found that ultrasonic waves could be used to arrange the fibers into appropriate patterns within the polymer. The precise orientation of each fiber could then be controlled by switching the ultrasonic standing wave pattern during the printing process.

“The ultrasound effectively creates a patterned force field in the liquid plastic and the fibers move to and align with low pressure regions in the field called nodes,” Llewellyn-Jones explained. “The fibers are then fixed in place using a tightly focused laser beam that cures (sets) the polymer.

Using a switchable, focused laser module mounted directly onto an off-the-shelf 3D printer, The team was able to reach print speeds of 20mm/s on its modified machine, a rate comparable to that of conventional 3D printers. The process could have great flexibility, and be used to create patterns not possible with traditional methods. Almost any type, size or shape of fiber can be used within the novel system, which gives product designers new possibilities within the realm of smart materials.

“Our work has shown the first example of 3D printing with real-time control over the distribution of an internal microstructure and it demonstrates the potential to produce rapid prototypes with complex microstructural arrangements,” said Bruce Drinkwater, Professor of Ultrasonics in the Department of Mechanical Engineering. “This orientation control gives us the ability to produce printed parts with tailored material properties, all without compromising the printing.”

“As well as offering reinforcement and improved strength, our method will be useful for a range of smart materials applications, such as printing resin-filled capsules for self-healing materials or piezoelectric particles for energy harvesting,” added Dr Richard Trask, Reader in Multifunctional Materials in the Department of Aerospace Engineering.

The team’s research paper, “3D printed components with ultrasonically arranged microscale structure”, was published today in Smart Materials and Structures. Although Llewellyn-Jones does not expect the technique to be adopted by major 3D printing companies in the immediate future, it could certainly be adopted by manufacturers after further testing and development.



Posted in 3D Printing Technology



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