P U B L I S H E R ’ S D E S K A novel 3D printing method yields unprecedented control of the arrangement of short fibres embedded in polymer matrices. (Image courtesy of Lewis Lab/Harvard SEAS) HEADS UP: THE WORLD IS CHANGING, FAST Welcome to the first edition of Engineering News for 2018. We trust you’ve had a safe and relaxing Christmas period, and are now amped with renewed energy to put into the engineering industry and your businesses. I found myself gob-smacked by saying 2018… to me, for some underlying reason unknowingly engrained, it’s two years off what as a child I perceived as a far-away future, 2020. That childhood definition involving infinite possibilities is now here - for me - or at least what’s actually arrived is the realisation that what was a mystifying entity that seemed so far away isn’t just knocking on the door it’s about to step through. Every single day new innovation occurs. And, within nearly every sector. The components that make up the engineering industry are not immune to change, and the great engineering companies and manufacturers of the future will be those that embrace that change and search for innovative ways to collaborate with like-minded companies and people. The world of 3D printing is one area in which change is occurring on a daily basis. As we go to press for this first issue, I’m hearing out of Harvard that a new type of 3D printing isn’t just being worked on but has been achieved. According to researchers, 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. But 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 fibres embedded in polymer matrices. They used this additive manufacturing technique to program fibre orientation within epoxy composites in specified locations, enabling the creation of structural materials that are optimised 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 fibre orientation within engineered composites has been a grand challenge,” said the study’s senior author, Jennifer Lewis, “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 but with a host of contributing collaborators. “Rotational 3D 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.” 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. 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 fibres can be locally optimised 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. More control over structure means more control over the resulting properties, which vastly expands the design space that can be exploited to optimise properties further. Another example of the future here today. www.engineeringnews.co.nz 3
EN-Feb18-eMag
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