Metals and plastics are the most common 3D-printed materials, but a new technique could allow 3D-printed composite materials to become much more common.

Researchers have demonstrated that ultrasonic waves can create composites with complex microstructures using an off-the-shelf 3D printer.

3D Printing with Ultrasonic Waves

The team used ultrasonic waves to position millions of tiny reinforcement fibers as part of the 3D printing process. These fibers form a microscopic framework that reinforces the material and increases its strength. The microstructure is set using a focused laser to locally cure the epoxy resin and print the object. The fibers’ orientation can be controlled by adjusting the ultrasonic standing wave pattern in mid-print.

Check out the video below to see the zoomed-in formation of the reinforcement pattern:

Tiny glass fibers form into a reinforcement pattern under the action of ultrasonic waves. (Video courtesy of Tom Llewellyn-Jones, Bruce Drinkwater and Richard Trask.)

What’s notable about this technique is the simplicity of its implementation: the research team mounted a switchable, focused laser module onto the carriage of a standard three-axis 3D printing stage above their ultrasonic alignment apparatus.

“We have demonstrated that our ultrasonic system can be added cheaply to an off-the-shelf 3D printer, which then turns it into a composite printer,” said Tom Llewellyn-Jones, an engineering PhD student at the University of Bristol who developed the system.

Using this technique, the team was able to achieve a print speed of 20mm/s, which is close to the average speed of a conventional 3D printer.

Applications for 3D-Printed Composite Materials

According to mechanical engineering professor Bruce Drinkwater, “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.”

“This orientation control gives us the ability to produce printed parts with tailored material properties, all without compromising the printing,” Drinkwater concluded.

His colleague, aerospace engineer Richard Trask added, "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."

For more information, see the open-access study published in Smart Materials and Structures.