A team of researchers at Harvard University’s John A Paulson School of Engineering and Applied Sciences (SEAS) (
www.seas.harvard.edu) has demonstrated a novel 3-D printing method that gives “unprecedented control” over the arrangement of short fibres embedded in polymer matrices.
They used this additive-manufacturing technique to program fibre orientation within epoxy composites in specified locations, thereby creating structural materials that are optimised for strength, stiffness and ‘damage tolerance’.
The team’s method, referred to as “rotational 3-D printing,” could have broad-ranging applications.
Given the ‘modular nature’ of their ink compositions, many different filler and matrix combinations can be implemented to tailor electrical, optical or thermal properties of the printed objects.
The study’s senior author, Jennifer Lewis, said: “Being able to locally control fibre orientation within engineered composites has been a grand challenge.
“We can now pattern materials in a hierarchical manner, akin to the way that nature builds.”
The work was carried out in the Lewis lab at Harvard, with collaborators that included Brett Compton (now assistant professor in mechanical engineering at the University of Tennessee).
He said: “Rotational 3-D printing can be used to achieve optimal — or near-optimal — fibre arrangements at every location in the printed part, resulting in higher strength and stiffness with less material.
“Rather than using magnetic or electric fields to orient fibres, we control the flow of the viscous ink itself to impart the desired fibre orientation.”
Mr Compton also said that the team’s nozzle concept could be used on any material extrusion printing method, from fused filament fabrication to direct ink writing to large-scale thermoplastic additive manufacturing — and with any filler material, from carbon and glass fibres to metallic or ceramic whiskers and platelets.
Commenting on this work, Lorna Gibson, who is professor of materials science and engineering at MIT (and was not involved in the research), said: “Biological composite materials often have remarkable mechanical properties: high stiffness and strength per unit weight and high toughness.
“One of the outstanding challenges of designing engineering materials inspired by biological composites is control of fibre orientation at small length scales and at the local level.
“This work demonstrates a way of doing just that. It represents a huge leap forward in the design of bio-inspired composites.”