Novel 3-D printing technique yields high-performance composites
by Staff Writers
Boston MA (SPX) Jan 16, 2018
Nature has produced exquisite composite materials - wood, bone, teeth, and shells, for example - that combine light weight and density with desirable mechanical properties such as stiffness, strength and damage tolerance.
Since ancient civilizations first combined straw and mud to form bricks, people have fabricated engineered composites of increasing performance and complexity. But reproducing the exceptional mechanical properties and complex microstructures found in nature has been challenging.
Now, a team of researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has demonstrated a novel 3D printing method that yields unprecedented control of the arrangement of short fibers embedded in polymer matrices.
They used this additive manufacturing technique to program fiber orientation within epoxy composites in specified locations, enabling the creation of structural materials that are optimized for strength, stiffness, and damage tolerance.
Their method, referred to as "rotational 3D printing," could have broad ranging applications. Given the modular nature of their ink designs, many different filler and matrix combinations can be implemented to tailor electrical, optical, or thermal properties of the printed objects.
"Being able to locally control fiber orientation within engineered composites has been a grand challenge," said the study's senior author, Jennifer A. Lewis, Hansjorg Wyss Professor of Biologically Inspired Engineering at Harvard SEAS.
"We can now pattern materials in a hierarchical manner, akin to the way that nature builds." Lewis is also a Core Faculty Member of the Wyss Institute for Biologically Inspired Engineering at Harvard.
The work, described in the journal PNAS, was carried out in the Lewis lab at Harvard. Collaborators included then-postdoctoral fellows Brett Compton (now Assistant Professor in Mechanical Engineering at the University of Tennessee, Knoxville), and Jordan Raney (now Assistant Professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania); and visiting PhD student Jochen Mueller from Prof. Kristina Shea's lab at ETH Zurich.
The key to their approach is to precisely choreograph the speed and rotation of a 3D printer nozzle to program the arrangement of embedded fibers in polymer matrices. This is achieved by equipping a rotational printhead system with a stepper motor to guide the angular velocity of the rotating nozzle as the ink is extruded.
"Rotational 3D printing can be used to achieve optimal, or near optimal, fiber arrangements at every location in the printed part, resulting in higher strength and stiffness with less material," Compton said.
"Rather than using magnetic or electric fields to orient fibers, we control the flow of the viscous ink itself to impart the desired fiber orientation."
Compton noted 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 fibers to metallic or ceramic whiskers and platelets.
The technique allows for the 3D printing of engineered materials that can be spatially programmed to achieve specific performance goals. For example, the orientation of the fibers can be locally optimized to increase the damage tolerance at locations that would be expected to undergo the highest stress during loading, hardening potential failure points.
"One of the exciting things about this work is that it offers a new avenue to produce complex microstructures, and to controllably vary the microstructure from region to region," Raney said.
"More control over structure means more control over the resulting properties, which vastly expands the design space that can be exploited to optimize properties further."
"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 fiber orientation at small length scales and at the local level," said Lorna J. Gibson, Professor of Materials Science and Engineering at MIT, who was not involved in the research.
"This remarkable paper from the Lewis group demonstrates a way of doing just that. This represents a huge leap forward in the design of bio-inspired composites."
London, UK (SPX) Jan 11, 2018
A new 3D printing technique allows researchers to replicate biological structures, which could be used for tissue regeneration and replica organs. Imperial College London researchers have developed a new method for creating 3D structures using cryogenics (freezing) and 3D printing techniques. This builds on previous research, but is the first to create structures that are soft enough ... read more
Harvard School of Engineering and Applied Sciences
Space Technology News - Applications and Research
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.