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Tennessee Students Help Navy Research 3-D Print Materials' Properties

20 March 2018
University of Tennessee, Knoxville (UTK), students have partnered with Naval Surface Warfare Center, Carderock Division to study the material side of additive manufacturing (AM).
University of Tennessee, Knoxville (UTK), students have partnered with Naval Surface Warfare Center, Carderock Division to study the material side of additive manufacturing (AM).

Specifically, the team wants to better understand how printing parameters such as nozzle temperature, cooling, sample size and print time affects the mechanical properties of the material, with the ultimate goal of qualifying components made from these materials for use in shipboard applications.

The project is part of the Naval Engineering Education Consortium (NEEC), which is a program that provides research 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 skills.

Dr. Stephanie TerMaath, a professor at UTK, and doctoral student William Ferrell presented their NEEC project March 13 at Carderock's West Bethesda, Maryland, headquarters. They stayed for the week to print additional test coupons to further understand the variability of printing on one model of a machine to another in the Manufacturing, Knowledge and Education (MAKE) Lab. In addition, they also were able to use some Code 60 facilities to perform thermal and mechanical testing on polymer AM materials that they had printed at UTK.

The UTK students weren't the only ones gaining knowledge during the visit to Carderock. Ferrell said he was also able to help employees in Carderock's Advanced Materials and Structures Branch fabricate a composite laminate in Carderock's Composites Lab using the vacuum-assisted resin transfer molding (VARTM) process.

TerMaath said the technical objective of this NEEC project, which is in its second year, 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.

"Can we take the current building-block approach to material qualification and part certification and supplement that with computational simulation to explore customized materials prior to comprehensive testing, especially when inserting emerging materials," TerMaath said. "We are starting to build our own materials for additive manufacturing, actually making our own custom filaments. So, as you do that, we don't necessarily want to do a full building-block test program for every potential design, so can we take validated computational models, use them to explore the whole design space and then do the building-block approach and the comprehensive testing on the most promising designs."

Dr. Maureen Foley, a materials engineer in Carderock's Integrated Manufacturing and Project Management Office, is the program manager for the NEEC with UTK.

"The research we are doing with the University of Tennessee is extremely relevant to our needs for the Navy," Foley said. "As additive manufacturing becomes more mainstream, we absolutely need to find ways to better understand how the various materials are affected by the printing parameters that can be changed by the user of the 3-D printers in order to qualify components for use in shipboard applications safely and quickly. The whole point of AM is to provide an option to print a part to maintain mission readiness. If we don't understand the variability of the 3-D printing process, it will be difficult to understand the risk of transitioning more critical polymer AM parts in the long run. These students are working through ways that we might be able to better understand the variability of the materials and printers and developing computational tools that can be used to perform simulations to be able to predict crack behavior. And when they graduate, hopefully they will come work with us."

Ferrell, who is working on his Ph.D. in materials science engineering, is one of the primary researchers for this particular NEEC project. During this second year the students are performing comprehensive testing to investigate crack growth with the goal of developing multi-scaled computational models that capture the resulting observations.

Ferrell said the focus of the previous year was in material characterization and establishing test programs and performing the mechanical testing of the materials and the parts to understand why the material was behaving in a specific manner.

"We want to be more predictive and be able to have more efficient qualification of future materials under marine conditions. If we put an AM part on a ship, we need to be able to predict what's going to happen in order to design against failure from it being hot, wet and salty," Ferrell said.

For year three, Ferrell said the goal is to do a concept demonstration. Through the work they are currently doing, they want to be able to create a demonstration part, test it, and then predict and model the crack behavior at a stress concentration such as a corner.

"The idea is once we have a part, we're still using that building-block approach, supplemented with knowledge on the uncertainty in material behavior due to print process variables. And at this point, we will be able to say, because of all these steps that we have taken over the past two years to quantify atomistically, molecular dynamically, all the way through structural analysis validated by the testing, that we understand variability in structural performance," Ferrell said. "We're moving towards repeatability - that way, our defense, our Sailors, our workers can all rely on the parts that are being printed in the future."

While they are working toward that technical goal, the students involved are preparing themselves for a potential career with a Navy lab. TerMaath said the students have been very interactive with her and with Carderock, especially Foley.

"I can't thank Dr. Foley enough, she emails, she helps them with resumes, she gives them advice, talks to them on the phone," TerMaath said. "She's been phenomenal. We couldn't ask for a better program manager."

According to the Naval Sea Systems Command (NAVSEA) Warfare Centers NEEC information website, the program offers students who may be interested in pursuing civilian science and engineering careers with the Navy the opportunity to investigate real Navy challenges while working hand-in-hand with university faculty and Navy mentors.

Garth Jensen, Carderock's director of innovation and NEEC program manager, said Carderock currently has three NEEC projects going on. He said the program has produced some of the Navy's finest employees.

"As Carderock's NEEC program manager, I have been privileged to witness first hand the profound impact this program is having on attracting fresh, young faces and growing them into this nation's next generation of Navy scientists and engineers," Jensen said.

Carderock is hosting the mid-Atlantic NEEC annual conference April 11, where the UTK project, as well as projects from other Warfare Centers, will be highlighted. Jensen said there will also be time for career counseling for the students interested in working in Navy labs. The meeting will include representatives from NSWC Dahlgren Division, NSWC Indian Head Explosives Ordnance Technology Division, and NSWC Philadelphia Division. Scheduled speakers include Don McCormack, Warfare Center executive director, and Rear Adm. David Hahn, chief of naval research.

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, Virginia (Little Creek); Port Canaveral, Florida; Fort Lauderdale, Florida; Memphis, Tennessee; Bangor, Washington; Ketchikan, Alaska; and Bayview, Idaho.

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