California-based Lawrence Livermore National Laboratory (LLNL) has a 60-year history of applying technology and science to make the world a safer place, and has a vision to be the premier destination for America’s best engineers and scientists. The researchers at LLNL have worked on all kinds of cutting-edge 3D printing technology, including the development graphene bio-inks, material strength testing, nanotechnology, and even 4D printing. LLNL has now announced that its researchers are the first to 3D print high-performance, aerospace-grade carbon fiber composites, which is a big foot in the door to optimization and greater control of the strong but lightweight material.LLNL’s study was funded by the Laboratory Directed Research and Development program, and was recently published online in Nature Science Reports; authors on the paper included lead author James Lewicki and co-authors Jennifer Rodriguez, Cheng Zhu, Marcus Worsley, Amanda Wu, John Horn, Jason Ortega, William Elmer, Ryan Hensleigh, Ryan Fellini, and Michael King. The research team explained that their work epitomizes a major advance in developing 3D printing micro-extrusion techniques for carbon fiber, which is actually stronger than steel. The stiff but light material has a high resistance to temperature, which makes it a popular choice in the automotive, aerospace, and defense industries, as well as in motorcycle racing and surfing.
Principal Investigator Jim Lewicki, LLNL Staff Scientist in the Materials Science Division, said, “The mantra is ‘if you could make everything out of carbon fiber, you would’ – it’s potentially the ultimate material. It’s been waiting in the wings for years because it’s so difficult to make in complex shapes. But with 3D printing, you could potentially make anything out of carbon fiber.”
There are two common ways that scientists generally fabricate carbon fiber composites. The first is physically winding the filaments around a mandrel, or weaving them together, kind of like you’re making a basket. According to Lewicki, this results in completed products that are only either cylindrical or flat. Also, the parts tend to wind up being more expensive, heavier, and more wasteful, because fabricators with concerns about performance have a tendency to overcompensate with the material.LLNL tackled this carbon fiber material overcompensation problem, and researchers reported that they were able to use a modified Direct Ink Writing (DIW) 3D printing process to create several complex 3D structures. Lewicki and the rest of the team were also able to develop a new chemistry, which they’ve now patented, that’s able to cure the material extremely fast – what used to take hours now only takes seconds with this new chemistry. The team developed accurate models of carbon fiber filament flow, thanks to LLNL’s “high performance computing capabilities.”
A team of engineers, using the LLNL supercomputers, completed the computational modeling Lewicki referenced. In order to determine how to best align the carbon fibers during the process, the engineers actually had to simulate thousands of these fibers as they came out of the ink nozzle.
Lewicki explained, “How we got past the clogging was through simulation. This has been successful in large part because of the computational models.”
Fluid analyst Yuliya Kanarska said, “We developed a numerical code to simulate a non-Newtonian liquid polymer resin with a dispersion of carbon fibers. With this code, we can simulate evolution of the fiber orientations in 3D under different printing conditions. We were able to find the optimal fiber length and optimal performance, but it’s still a work in progress. Ongoing efforts are related to achieving even better alignment of the fibers by applying magnetic forces to stabilize them.”
The researchers said that 3D printing is able to afford them more freedom for handling the carbon fiber material, and gives them more control over the mesostructure of the parts they are creating. The conductive material also allows for directed thermal channeling within a structure, which could be used to fabricate high-performance airplane wings, wearables that are able to draw body heat without allowing it in, and satellite components that are insulated on just one side, negating rotation in the vacuum of space.
The process of DIW also allows the researchers to 3D print parts which outperform similar materials created using other methods, because direct ink writing makes it possible for the carbon fibers to all go in the same direction, instead of being randomly aligned. This way, two-third less carbon fiber is used, cutting back on material waste, and still lets the finished part get the same material properties. Take a look at LLNL’s short video, to see a computer animation that simulates how the carbon fibers align and extrude through a 3D printing nozzle:
“A big breakthrough for this technology is the development of custom carbon fiber-filled inks with thermoset matrix materials. For example, epoxy and cyanate ester are carefully designed for our printing process, yet also provide enhanced mechanical and thermal performance compared to thermoplastic counterparts that are found in some commercially available carbon fiber 3D printing technologies, such as nylon and ABS (a common thermoplastic). This advance will enable a broad range of applications in aerospace, transportation and defense,” explained LLNL materials and advanced manufacturing researcher Eric Duoss.
The next step for the LLNL carbon fiber research team will be optimizing the process, and determining the best places to lay down the material in order to get the best possible performance. The team has also been in discussions with possible aerospace, commercial, and defense partners, in order to continue developing the technology in the future. Discuss in the LLNL forum at 3DPB.com.[Source: LLNL]