Tag Archives: carbon fibres

Let’s make our turbine blades really big (greater than 75 metres) with new nanocomposite

The is a story about balsa wood, wind farms, turbine blades, and nanocomposites according to a June 25, 2014 news item on ScienceDaily,

In wind farms across North America and Europe, sleek turbines equipped with state-of-the-art technology convert wind energy into electric power. But tucked inside the blades of these feats of modern engineering is a decidedly low-tech core material: balsa wood.

Like other manufactured products that use sandwich panel construction to achieve a combination of light weight and strength, turbine blades contain carefully arrayed strips of balsa wood from Ecuador, which provides 95 percent of the world’s supply.

For centuries, the fast-growing balsa tree has been prized for its light weight and stiffness relative to density. But balsa wood is expensive and natural variations in the grain can be an impediment to achieving the increasingly precise performance requirements of turbine blades and other sophisticated applications.

As turbine makers produce ever-larger blades — the longest now measure 75 meters, almost matching the wingspan of an Airbus A380 jetliner — they must be engineered to operate virtually maintenance-free for decades. In order to meet more demanding specifications for precision, weight, and quality consistency, manufacturers are searching for new sandwich construction material options.

Now, using a cocktail of fiber-reinforced epoxy-based thermosetting resins and 3D extrusion printing techniques, materials scientists at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering have developed cellular composite materials of unprecedented light weight and stiffness.

A June 25, 2014 Harvard University news release (also on EurekAlert), which originated the news item, goes on to describe the new technology in more detail while throwing 3D printing into the mix,

Until now, 3D printing has been developed for thermo plastics and UV-curable resins—materials that are not typically considered as engineering solutions for structural applications. “By moving into new classes of materials like epoxies, we open up new avenues for using 3D printing to construct lightweight architectures,” says principal investigator Jennifer A. Lewis, the Hansjörg Wyss Professor of Biologically Inspired Engineering at Harvard SEAS. “Essentially, we are broadening the materials palate for 3D printing.”

“Balsa wood has a cellular architecture that minimizes its weight since most of the space is empty and only the cell walls carry the load. It therefore has a high specific stiffness and strength,” explains Lewis, who in addition to her role at Harvard SEAS is also a Core Faculty Member at the Wyss Institute. “We’ve borrowed this design concept and mimicked it in an engineered composite.”

Lewis and Brett G. Compton, a former postdoctoral fellow in her group, developed inks of epoxy resins, spiked with viscosity-enhancing nanoclay platelets and a compound called dimethyl methylphosphonate, and then added two types of fillers: tiny silicon carbide “whiskers” and discrete carbon fibers. Key to the versatility of the resulting fiber-filled inks is the ability to control the orientation of the fillers.

The direction that the fillers are deposited controls the strength of the materials (think of the ease of splitting a piece of firewood lengthwise versus the relative difficulty of chopping on the perpendicular against the grain).

Lewis and Compton have shown that their technique yields cellular composites that are as stiff as wood, 10 to 20 times stiffer than commercial 3D-printed polymers, and twice as strong as the best printed polymer composites. The ability to control the alignment of the fillers means that fabricators can digitally integrate the composition, stiffness, and toughness of an object with its design.

“This paper demonstrates, for the first time, 3D printing of honeycombs with fiber-reinforced cell walls,” said Lorna Gibson, a professor of materials science and mechanical engineering at the Massachusetts Institute of Technology and one of world’s leading experts in cellular composites, who was not involved in this research. “Of particular significance is the way that the fibers can be aligned, through control of the fiber aspect ratio—the length relative to the diameter—and the nozzle diameter. This marks an important step forward in designing engineering materials that mimic wood, long known for its remarkable mechanical properties for its weight.”

“As we gain additional levels of control in filler alignment and learn how to better integrate that orientation into component design, we can further optimize component design and improve materials efficiency,” adds Compton, who is now a staff scientist in additive manufacturing at Oak Ridge National Laboratory. “Eventually, we will be able to use 3D printing technology to change the degree of fiber filler alignment and local composition on the fly.”

The work could have applications in many fields, including the automotive industry where lighter materials hold the key to achieving aggressive government-mandated fuel economy standards. According to one estimate, shedding 110 pounds from each of the 1 billion cars on the road worldwide could produce $40 billion in annual fuel savings.

3D printing has the potential to radically change manufacturing in other ways too. Lewis says the next step will be to test the use of thermosetting resins to create different kinds of architectures, especially by exploiting the technique of blending fillers and precisely aligning them. This could lead to advances not only in structural materials, but also in conductive composites.

Previously, Lewis has conducted groundbreaking research in the 3D printing of tissue constructs with vasculature and lithium-ion microbatteries.

Here’s a link to and citation for the paper,

3D-Printing of Lightweight Cellular Composites by Brett G. Compton and Jennifer A. Lewis. Advanced Materials DOI: 10.1002/adma.201401804 Article first published online: 18 JUN 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Lighter, tougher gas tanks (to transport more natural gas) coming from 3M and Chesapeake Energy

They certainly have given the news of their (3M and Chesapeake Energy’s, that is) collaboration with an upbeat yet deeply concerned (about breaking the “foreign stranglehold” on energy imports) tone. From the Feb. 28, 2012 news item on Nanowerk,

“3M believes in the potential of natural gas, and this agreement illustrates our commitment to the industry,” said George Buckley, Chairman, President and Chief Executive Officer of 3M. “We are excited about this collaboration to speed the development and adoption of natural gas-powered vehicles.” [emphasis mine]

Increased political support and private investment have made natural gas a viable automotive fuel alternative with large growth potential. With more than a 100-year supply of natural gas in the United States and an average price per gasoline gallon equivalent of $1.00 to $2.00, the fuel is plentiful, affordable and domestic. [emphasis mine] The fuel also burns more cleanly than gasoline, cutting greenhouse gas emissions by 30 percent and particulate matter by 95 percent.

“This partnership brings together two leading companies from different sectors, both committed to advancing the natural gas transportation fuel market,” said Aubrey K. McClendon, Chesapeake’s Chief Executive Officer. “We applaud 3M for recognizing the future of natural gas as a low-cost, cleaner alternative to gasoline, and for creating innovative tank technology that will make natural gas vehicles more affordable and accessible to fleets and individual consumers nationwide. Our country needs a solution to break the foreign stranglehold on our fuels market, and today’s announcement is another step to transition our nation away from costly imports.” [emphasis mine]

The companies will be using a nanotechnology-enabled solution to making the tanks, which hold the natural gas, stronger and lighter. From the 3M/Chesapeake Energy Feb. 21, 2012 press release,

3M’s CNG [compressed natural gas] tank solution combines the company’s proprietary liner advancements, thermoplastic materials, barrier films and coatings, and damage-resistant films to transform the pressure vessel industry. Using nanoparticle-enhanced resin technology, 3M™ Matrix Resin for Pressure Vessels, 3M will create CNG tanks that are 10 to 20 percent lighter with 10 to 20 percent greater capacity, all at a lower cost than standard vessels. In addition to these benefits, the 3M technology produces safer and more durable tanks than those currently on the market. This tank innovation builds on 3M’s proven history of developing and introducing pioneering technologies to the market.

I’m wondering how the estimate for that “100 year supply of natural gas  in the US” was derived. It stands to reason that if you make natural gas an attractive alternative to current fuels that its use will increase, perhaps exponentially, should more uses for natural gas be discovered than simply as a ‘replacement’ for current fuels.

I did check out Chesapeake Energy, a company based in Oklahoma City, Oklahoma, and not in a New England state (I think Chesapeake Bay is in Massachusetts) as I was expecting. Here’s an excerpt from the company’s home page,

We’re the second-largest producer of natural gas, a Top 15 producer of oil and natural gas liquids and the most active driller of new wells in the U.S. Headquartered in Oklahoma City, the company’s operations are focused on discovering and developing unconventional natural gas and oil fields onshore in the U.S. Chesapeake owns leading positions in the Barnett, Haynesville, Bossier, Marcellus and Pearsall natural gas shale plays and in the Granite Wash, Cleveland, Tonkawa, Mississippi Lime, Bone Spring, Avalon, Wolfcamp, Wolfberry, Eagle Ford, Niobrara and Utica unconventional liquids plays.

I also found out a little more about the technology that 3M will be incorporating in the new gas tanks (from the 3M™ Matrix Resin Technology page),

Carbon fiber composite products are limited by their compression strength. Under compressive loading, carbon fibers can micro-buckle (like a small wrinkle) resulting in breaking or failure of the composite product.

Creating a resin with a high concentration of uniformly dispersed nanoparticles makes a stronger composite. These nanoparticles are so tiny, they can uniformly surround and support the carbon fibers, significantly increasing the shear modulus of the resin, and effectively delaying the micro-buckling of the carbon fibers. The greater the nanoparticle loading, the stiffer the support of the carbon fiber. Where other nanotechnologies (like carbon nano tubes) deliver <3% nanoparticles loading, 3M’s proprietary technology uniquely enables loadings of >40% of uniformly dispersed nanoparticles.

3M’s ability to significantly increase resin shear modulus is a game changer in and of itself. But 3M’s technology truly bends the rules by simultaneously increasing fracture toughness. In the past, attempts to increase resin stiffness resulted in a significant decrease in fracture toughness, producing very brittle materials. 3M’s proprietary nanoparticles technology creates such a strong bond between the particle and the resin, that energy is dissipated when the composite is stressed, preventing crack propagation.

I am curious as to exactly what those nanoparticles might be made of but I gather that is proprietary information