University of Delaware TuFF composite material shows high potential for UAM

High-performance, short-fiber composite offers aerospace-grade properties with the potential to offer costs and production rates similar to those found in the automotive industry.
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High-performance composite material, TuFF.

University of Delaware researchers have developed a new high-performance material, known as TuFF (Tailored Universal Feedstock for Forming), with properties equivalent to continuous fiber composites used in aerospace applications. Like sheet metal, TuFF can be stamped into complex shapes. Photo Credit: University of Delaware Center for Composite Materials.

According to research developers at the University of Delaware’s (UD) Center for Composite Materials (CCM), target applications for its high-performance, short-fiber composite material, TuFF (Tailored Universal Feedstock for Forming), may be far-reaching. High strength, ultra-lightweight and highly durably, UD says highly potential markets include defense, oil and gas and even electrical vertical take-off and landing (eVTOL) aircraft. 

Developed as part of a Defense Advanced Projects Agency (DARPA, Arlington, Va., U.S.) Defense Sciences Office program, TuFF is said to have properties equal to composites used in space and aerospace applications. And, according to CCM Director Jack Gillespie, the uses for TuFF are starting to take off.

Gillespie says in 2020 alone, the composite material led to nearly $20 million in federal funding to advance new applications for TuFF across four projects from the National Aeronautics and Space Administration (NASA), the Advanced Research Projects Agency-Energy (ARPA-E), the Office of Naval Research (ONR) and the Department of Energy (DOE).

CCM researchers are currently working on ways to apply this core technology, which has the potential to help enable high-speed composites manufacturing, play a role in eVTOL development, repair infrastructure and improve manufacturing capabilities to produce the ultra-lightweight material with aerospace properties at costs and production rates like those found in the automotive industry. Additional ongoing work is supported by more than $15 million in funding from DARPA to date.


Repairing natural gas pipelines

Much of the U.S. infrastructure that links natural gas production to consumers has been in place for half a century. Some of it is in serious need of repair, including steel pipelines that deliver natural gas to factories and homes. Current repair methods involve digging up and replacing the aging pipes, a costly and time-consuming process.

CCM researchers are devising a way to use TuFF as an internal wrap for rapidly repairing existing gas pipelines in place, armed with $5.9 million in ARPA-E funding. The proposed method involves building a composite pipe-within-a-pipe without shutting the gas service off. It will avoid costly shutdowns in service necessary with other repair techniques and mitigate the huge societal cost of bringing a downed system back online.

The method involves using robots to lay down the composite TuFF material inside the pipeline, using the existing steel tube as a mold, and then employing UV light to cure the material in place as the robot moves along. This approach will extend the distance over which repairs can be done at any one time, since there is no need to shut the pipeline down while the robots work. Such robots for this task are currently being built, and sensors, imaging technology and integrated systems necessary for the job are currently being designed and tested by the CCM team.

“The outside metal pipe can rust in place, leaving behind a structurally and functionally sound composite pipe in its place,” explains Gillespie.

When in use, an initial robot will enter the pipeline, scan and digitize the pipe’s specific geometry one section at a time, and send that information to a second robot standing ready to follow along behind and lay down the TuFF resin-impregnated, short-fiber material against the existing tube. Because it is stretchable, TuFF will conform to complex pipe geometry and can be compressed to remove potential material defects, resulting in high-quality material and material properties. The new TuFF pipe will be cured under UV lights tethered to the rear of the robot, eliminating the need to use high temperatures to harden the material and ensuring overall process safety.

“These pipelines have long sections of cylindrical pipe, but then you might have junctions, curves or places where the diameter of the pipe is reduced. This is where TuFF really shines, because it can stretch and accommodate irregular shapes, which currently isn’t possible with other methods,” says Gillespie.


eVTOL aircraft

As the emerging urban air mobility (UAM) market continues to grow, it will require ultra-lightweight materials typically used for aerospace applications. However, according to CCM, one barrier is that currently there is no continuous fiber manufacturing process in place to handle creating aerospace-grade hardware at speeds and costs of other automotive parts. The only things similar are processes for injection-molded automotive parts like dashboards, knobs and intake manifolds. But these injection-molded parts are heavy and have poor material properties, which isn’t acceptable for aircraft that are electric powered and have ultralight composite bodies.

“What they need are materials that have aerospace performance but can be formed at automotive rates. There’s no process in the world that allows you to achieve this production rate. NASA identified this as a problem — and CCM knew they had the perfect solution — TuFF,” Gillespie says.

TuFF materials, says CCM research developers, offer equivalent properties to their currently available composite counterparts. TuFF materials also retain control over the direction and properties of the fibers for design and optimization but can be stamped like metal within minutes into complex geometry parts. And because it can be made using any fiber and any resin, TuFF opens the door to exploring a wide range of materials and material combinations.

CCM researchers are currently focused on developing modeling and simulation tools to design the material, the manufacturing process and the parts using TuFF materials, through $5.9 million in project funding from NASA’s University leadership Initiative. The project, led at UD by Gillespie, leverages CCM’s 9,000 square-foot TuFF integrated pilot manufacturing facility and includes collaboration with industry partners Joby Aviation (Santa Cruz, Calif., U.S.) and Spirit AeroSystems (Wichita, Kan., U.S.), Advanced Thermoplastics Composites Manufacturing (Post Falls, Ida., U.S.), as well as with colleagues at Southern University in Baton Rouge, La., U.S..

So, where do you go for ideas to scale something that hasn’t been done before? Gillespie says CCM is reaching out to nontraditional manufacturing industries, like the nonwoven paper industry for solutions they can adapt.

While vastly different industries, paper and TuFF are both materials composed of many short fibers that are pressed together with added binders. The difference is that TuFF composites are made by taking short structural fibers and aligning them to perfection.

Gillespie and others in CCM are considering ways to adapt the paper production framework for composites by adding a plug-in module for the fiber-alignment process. The result would be the ability to create materials at a fraction of the current cost, at production rates high enough that it could be scaled for different markets. And while the method would require water resources, the water itself could be recycled, making the process green.

In a separate project with $5.4 million in Office of Naval Research (ONR) funding, CCM researchers are teaming up with Arkema (Cologne, Germany, and King of Prussia, Penn., U.S.) to integrate TuFF technology with high-performance thermoplastics to create small aircraft parts in a way that is safe, more affordable, repeatable and scalable. The project expands on CCM’s ongoing DARPA work to advance lightweight material technologies  for military platforms, such as fighter aircraft.


Speaking of recycling

CCM researchers also are exploring ways to reuse recycled composite material fibers. In one project, researchers are taking outdated airplane parts that have been chopped into short fibers and recombining them to make the same material (or a better one) again.

With TuFF, Gillespie says, it’s possible to take a product that is at the end of its material lifespan, break the material back down into its components, realign the carbon fibers and create the same material, with the same properties and the same — or better — value, and have better processing and the ability to make complex geometry parts at large cost-savings. From an energy perspective, the embodied energy cost of the material is dramatically reduced over its lifetime.

“It could mean premium materials at a fraction of the cost,” he says. “That would greatly reduce manufacturing process costs because of the ability to stamp-form the material like metal, instead of by hand, for aircraft and spacecraft applications. So, instead of taking a month to make a part, we could do it in minutes.”

In another project, CCM researchers will apply this same technique to tackle challenges in plastic waste with $2.49 million recently awarded as part of the U.S. Department of Energy (DOE) BOTTLE Consortium (Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment). Here, the research team plans to upcycle short recycled structural fibers with polymers from recycled plastic bottles or other bio-based polymers to create TuFF composites, increasing the value of both materials.

Gillespie calls TuFF a “great success story” for UD and for federally funded research, as all of these new projects have spun out of one core technology (TuFF) developed through high-risk, high-reward research funded in 2016 by DARPA. It also is a great example of interdisciplinary collaboration at work, since the project includes contributions from researchers with expertise in mechanical engineering, materials science and engineering, civil engineering, electrical and computer engineering and CCM professional staff.

And CCM researchers are just getting started.

“If you put it all together, we can create materials for all of these applications that are 10 times more affordable than current materials — all without sacrificing performance,” he says. “So, when I talk about changing the paradigm of composites in the world and taking over the world market, I’m serious.”

This article was provided by University of Delaware, and originally reported by Karen B. Roberts.