WEST BETHESDA, Md. (NNS) -- University of Tennessee, Knoxville (UTK) doctoral student Will Ferrell and Dr. Stephanie TerMaath, professor of mechanical, aerospace and biomedical engineering, presented updated research on composite parts fabricated through polymer additive manufacturing as part of a collaboration with Naval Surface Warfare Center, Carderock Division (NSWCCD), Jan. 22.
For the past few years, the UTK team has been working alongside different branches at Carderock to better understand how printing parameters, such as nozzle temperatures, cooling, sample size and print time, affect the mechanical properties of the material. The ultimate goal is to qualify components made from these materials for use in shipboard applications.
This three-year project is part of the Naval Engineering Education Consortium (NEEC), which is a program that provides funding for relevant research at academic institutions and provides opportunities for students to participate in hands-on research during the academic year to develop their technical abilities. The educational objective is to prepare students for careers with the Navy, while accomplishing the technical objective. This program provides the students with daily hands-on technical training, interaction with Navy personnel and recruiters and helps them to develop a diverse, multi-disciplinary workforce. Currently, there are three NEEC projects funded at Carderock, overseen by Science, Technology, Engineering and Math (STEM) and Outreach Program Director Charlotte George.
The technical objective for the UTK NEEC contract, which ends in May, is to explore and demonstrate the potential of an integrated experimental and computational approach to the qualification process of composite parts fabricated with embedded fibers.
These UTK students have worked with Carderock employees in the Integrated Manufacturing and Project Management Office, as well as the Advanced Materials and Structures Branch, as TerMaath also had an Office of Naval Research Young Investigator Project (ONR YIP) on composite patches. Materials engineer Dr. Maureen Foley in Code 6102 is the technical point of contact for the NEEC with UTK. Originally working through the building-block approach through comprehensive testing, the UTK team found this to be cost-prohibitive due to the sheer number of tests needed. They instead have been operating on an integrated and automated simulation environment to supplement physical testing.
“What we’re looking at for additive manufacturing and composites is how can we make it so that we don’t have to test everything, and instead, we can look at new and emerging materials that have already been tested and proven to be effective," TerMaath said. "It would be the ideal case that someone could go into a database and look at all of the material choices, select the constituents and configuration, perform a multi-scale structural analysis through modeling and simulation, run some tests to evaluate reliability and optimize the design, and then in the end, come out with a new, reliable part.”
With this hybrid-structure database, the team would be able to test material properties, boundary conditions, probabilistic distributions, loading conditions, uncertainty and data quality information, loading conditions and analytical models. With this database, they would also have the opportunity to design guidelines and do results analysis. Allowing the user to first select their constituents and configuration has the benefit of allowing them to explore many different combinations. They would then be able to perform a multi-scale, structural analysis, varying the fidelity at each scale and investigating multiple loading conditions. Lastly, the database would allow for the evaluation of the material’s reliability and optimize its design. This would help to minimize the cost and weight of the material and maximize performance. This hybrid-structure database design would then allow the team to perform uncertainty quantification for design optimization on the new material.
While at Carderock, the UTK students leveraged the ONR YIP grant TerMaath had in the area of composite patches to extend the collaborative activities that could take place. The students have worked alongside aerospace engineer Daniel Hart in Carderock’s Structural Composites Branch in the lab, laying down the materials to create composite patches. It takes between 12 and 14 hours for a patch to be ready to be tested. Once those patches are created, they are put through tension and compression tests to evaluate how much the patch elongates and how strong it is before it breaks.
In the classification stage, they have concluded that specimen size affects strength and repeatability. Specific geometry and specification to the number of beads required in cross-sectioning those parts may be pertinent to achieve geometry independent properties. They also found that matching the specimen size and processing conditions is necessary for accurate qualification. In the processing stage, they concluded the layer time and process control can lead to stronger prints and less variable prints. Lastly, in the methodologies, they concluded that sequential prints could produce slightly weaker prints, but with increased repeatability and more prints per unit; cutting methods need to be reported for consistency; and printer variability exists and should be included in the variability processes where machines need to be qualified as well.
Ongoing work includes predicting fracture behavior of demonstration parts; informing finite element models using peridynamics results; and quantifying uncertainty using non-deterministic modeling, such as length, density, orientation, air voids and dimensional variation.
Naval Surface Warfare Center, Carderock Division, a part of Naval Sea Systems Command, leads the Navy in hull, mechanical and electrical engineering. Headquartered in West Bethesda, Maryland, Carderock Division employs approximately 2,000 scientists, engineers, technicians and support personnel and includes detachments in Norfolk (Little Creek); Port Canaveral, Florida; Fort Lauderdale, Florida; Memphis, Tennessee; Bangor, Washington; Ketchikan, Alaska; and Bayview, Idaho.
For more news from Naval Surface Warfare Center Carderock, visit www.navy.mil/local/nswcc/.