SMASH Alloys Being Designed to Improve Aerospace Safety Margins
Posted: 2013-9-21
By:
Bob Granath
Source:
NASA's Kennedy Space Center, Fla.
A future spacecraft landing on a distant planet may have an improved margin of
safety due to innovative metal alloys being developed at NASA's Kennedy Space
Center in Florida. Called "SMASH," Shape Memory Alloy Self-Healing is a
technology that creates metals that, when damaged, can repair themselves.
Aircraft and spacecraft can be subject to material fatigue, the progressive and
localized structural damage that occurs when a material is subjected to repetitive
stress.
"This technology could be used on deep-space missions to destinations such as
Mars or for high-performance aircraft," said Clara Wright, a materials engineer in
NASA's Engineering and Technology Directorate and the principal investigator for
the project.
Earlier this year, the NASA Aeronautics Research Institute (NARI) awarded an 18-
month, $275,000 follow-on Phase II seedling funding award to continue research
and development of the alloy that can self-repair fatigue damage in metallic
structures of aerospace vehicles using liquid-assisted shape memory metals.
NARI is part of the agency's Aeronautics Research Mission Directorate (ARMD)
and was established to invest in innovative, early-stage and potentially
revolutionary aviation concepts and technologies.
This is the first time that a Kennedy-led team has been selected for both the
Phase I and Phase II seedling award in this type of project. The NARI Seedling
Fund provides NASA civil servants the opportunity to perform research, analysis
and proof-of-concept development of ideas that have the potential to meet
national aeronautics needs.
Phase I of the project began in June of last year, as part of a collaborative
research effort with Michele Manuel, Ph. D., professor of Materials Science and
Engineering at the University of Florida.
"We have been working with Dr. Manuel in applied failure analysis, mentoring
and outreach activities for years," Wright said. "She had a proof-of-concept,
non-structural material for self-repairing metal structures and was looking for
potential applications. We had the opportunity to further the work and find
aeronautical and aerospace applications. That's how we at Kennedy became
involved."
Wright works in Kennedy's Materials and Process Engineering Branch and within
the failure analysis laboratory where experts determine why structures break
down and how to avoid future malfunctions.
"Much of the work is to make sure that when we're designing hardware, we're
using the right materials for the right applications," Wright said.
During Phase I, and leveraging a NASA Early Career Faculty Award, the SMASH
team developed structural alloys that could self-repair fatigue cracks.
The Phase II SMASH team researchers include Catherine Brinson, Ph. D.,
professor and chair of Mechanical Engineering at Northwestern University in
Illinois, and Terryl Wallace, Ph. D., of Structural Materials Engineering at NASA's
Langley Research Center in Virginia. For Phase II, Northwestern will be using
finite element modeling to determine the best alloy reinforcement, while Langley
will be supporting fabrication and potential applications for both aeronautical
vehicles and spacecraft.
"The alloys being developed are to be used in critical locations where fatigue
crack propagation fractures would likely occur," Wright said. "We'd use them in
areas where we can predict stress localization that might cause fatigue on
aircraft structural parts, such as where the wings attach to the fuselage or areas
that involve repetitive motion such as the landing gear."
Wright points out that for spacecraft traveling far from Earth, a repair shop would
not be an option.
"This is all about finding ways to mitigate potential damage from stress and
coming up with a good answer to that problem," she said. "Once a spacecraft is
well beyond Earth, anything we can do to stop crack propagation and prevent a
failure will improve our safety margins."
The SMASH technology begins with adding to metal alloys "shape-memory wire,"
similar to that used in dental braces.
"Once shaped, memory wire will want to return to its original form," said Wright,
"so if stress bends a metal component out of its designed shape, it will want to
return to its proper form."
The key to shape memory wire returning to its designed shape is heat.
"In the case of dental braces, the heat in the person's mouth keeps the braces in
the correct shape, pulling the teeth in the desired position," she said. "For the
SMASH aerospace alloys, if a fatigue crack begins, the shape memory alloys
reinforcements will stretch across the crack. Heating the wires will pull the metal
crack surfaces back together and the elevated temperatures also will cause low
melting phase in the alloy to become liquefied to fill in any gaps."
SMASH technology researchers are now testing three different types of aluminum
alloys newly developed at the University of Florida: aluminum-silicon, aluminum-
copper, and aluminum with both silicon and copper.
"Much of our testing has focused on which alloy works best," Wright said. "So far,
our research indicates that all the alloys retain about 90 percent of the strength
after repair. Our next steps are to determine what an alloy's fatigue life and
reliability is once it has been repaired."
Wright noted researchers will soon begin developing larger-scale samples,
different reinforcement architectures, as well as testing and using non-
destructive evaluations to confirm that the concepts work.
"We also want to determine how to best fabricate the metal and then test it," she
said.
Advanced analysis may take place on the International Space Station.
"We want to expose the materials to atomic oxygen and the microgravity
environment of both inside and outside of the space station," Wright said. "We'd
probably leave the samples up there for between six months to a year to
determine any effects of the space environment on the repair capacity of the
alloys."
Wright explains that putting the technology to work in actual aircraft or
spacecraft is still about eight to 10 years away.
"We've come a long way in the time since the project began last year," she said.
"We have until February of 2015 to complete the work under phase two (of the
NARI award). In the Failure Analysis Lab, we are usually trying to figure out why
something failed. The SMASH Project is giving us an opportunity to determine
how to prevent failures in the first place."
safety due to innovative metal alloys being developed at NASA's Kennedy Space
Center in Florida. Called "SMASH," Shape Memory Alloy Self-Healing is a
technology that creates metals that, when damaged, can repair themselves.
Aircraft and spacecraft can be subject to material fatigue, the progressive and
localized structural damage that occurs when a material is subjected to repetitive
stress.
"This technology could be used on deep-space missions to destinations such as
Mars or for high-performance aircraft," said Clara Wright, a materials engineer in
NASA's Engineering and Technology Directorate and the principal investigator for
the project.
Earlier this year, the NASA Aeronautics Research Institute (NARI) awarded an 18-
month, $275,000 follow-on Phase II seedling funding award to continue research
and development of the alloy that can self-repair fatigue damage in metallic
structures of aerospace vehicles using liquid-assisted shape memory metals.
NARI is part of the agency's Aeronautics Research Mission Directorate (ARMD)
and was established to invest in innovative, early-stage and potentially
revolutionary aviation concepts and technologies.
This is the first time that a Kennedy-led team has been selected for both the
Phase I and Phase II seedling award in this type of project. The NARI Seedling
Fund provides NASA civil servants the opportunity to perform research, analysis
and proof-of-concept development of ideas that have the potential to meet
national aeronautics needs.
Phase I of the project began in June of last year, as part of a collaborative
research effort with Michele Manuel, Ph. D., professor of Materials Science and
Engineering at the University of Florida.
"We have been working with Dr. Manuel in applied failure analysis, mentoring
and outreach activities for years," Wright said. "She had a proof-of-concept,
non-structural material for self-repairing metal structures and was looking for
potential applications. We had the opportunity to further the work and find
aeronautical and aerospace applications. That's how we at Kennedy became
involved."
Wright works in Kennedy's Materials and Process Engineering Branch and within
the failure analysis laboratory where experts determine why structures break
down and how to avoid future malfunctions.
"Much of the work is to make sure that when we're designing hardware, we're
using the right materials for the right applications," Wright said.
During Phase I, and leveraging a NASA Early Career Faculty Award, the SMASH
team developed structural alloys that could self-repair fatigue cracks.
The Phase II SMASH team researchers include Catherine Brinson, Ph. D.,
professor and chair of Mechanical Engineering at Northwestern University in
Illinois, and Terryl Wallace, Ph. D., of Structural Materials Engineering at NASA's
Langley Research Center in Virginia. For Phase II, Northwestern will be using
finite element modeling to determine the best alloy reinforcement, while Langley
will be supporting fabrication and potential applications for both aeronautical
vehicles and spacecraft.
"The alloys being developed are to be used in critical locations where fatigue
crack propagation fractures would likely occur," Wright said. "We'd use them in
areas where we can predict stress localization that might cause fatigue on
aircraft structural parts, such as where the wings attach to the fuselage or areas
that involve repetitive motion such as the landing gear."
Wright points out that for spacecraft traveling far from Earth, a repair shop would
not be an option.
"This is all about finding ways to mitigate potential damage from stress and
coming up with a good answer to that problem," she said. "Once a spacecraft is
well beyond Earth, anything we can do to stop crack propagation and prevent a
failure will improve our safety margins."
The SMASH technology begins with adding to metal alloys "shape-memory wire,"
similar to that used in dental braces.
"Once shaped, memory wire will want to return to its original form," said Wright,
"so if stress bends a metal component out of its designed shape, it will want to
return to its proper form."
The key to shape memory wire returning to its designed shape is heat.
"In the case of dental braces, the heat in the person's mouth keeps the braces in
the correct shape, pulling the teeth in the desired position," she said. "For the
SMASH aerospace alloys, if a fatigue crack begins, the shape memory alloys
reinforcements will stretch across the crack. Heating the wires will pull the metal
crack surfaces back together and the elevated temperatures also will cause low
melting phase in the alloy to become liquefied to fill in any gaps."
SMASH technology researchers are now testing three different types of aluminum
alloys newly developed at the University of Florida: aluminum-silicon, aluminum-
copper, and aluminum with both silicon and copper.
"Much of our testing has focused on which alloy works best," Wright said. "So far,
our research indicates that all the alloys retain about 90 percent of the strength
after repair. Our next steps are to determine what an alloy's fatigue life and
reliability is once it has been repaired."
Wright noted researchers will soon begin developing larger-scale samples,
different reinforcement architectures, as well as testing and using non-
destructive evaluations to confirm that the concepts work.
"We also want to determine how to best fabricate the metal and then test it," she
said.
Advanced analysis may take place on the International Space Station.
"We want to expose the materials to atomic oxygen and the microgravity
environment of both inside and outside of the space station," Wright said. "We'd
probably leave the samples up there for between six months to a year to
determine any effects of the space environment on the repair capacity of the
alloys."
Wright explains that putting the technology to work in actual aircraft or
spacecraft is still about eight to 10 years away.
"We've come a long way in the time since the project began last year," she said.
"We have until February of 2015 to complete the work under phase two (of the
NARI award). In the Failure Analysis Lab, we are usually trying to figure out why
something failed. The SMASH Project is giving us an opportunity to determine
how to prevent failures in the first place."
