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Team
UAH says, "We rely on 'STARS'
(Strategically Tuned Absolutely Resilient Structures)."
Our boat is a Strategically Tuned
Absolutely Resilient Structure (STARS) that acts as an energy storage device.
"STARS"
are unique in that their component materials are purposefully stressed and
deformed to the largest extent possible to store the maximum amount of potential
energy. They are designed based on
the strength, stiffness, and the position of the component materials in the
composite section and are therefore more complex and versatile compared to
simple energy storage devices such as springs.
The
ability of STARS to store and release energy depends upon a complex interaction
between the shape, modal response, and the forcing function applied to drive the
structure.
STARS
have captured the attention of the U.S. Congress, NASA, and the DoD.
Faculty at UAH have secured funding to build facilities and exploit the
underlying technology. A STARS class was offered at UAH this past semester
and efforts initiated there spawned a new corporate start, called Optechnology,
Inc., via the U.S. Army’s Small Business Innovative Research program.
Kirk
Biszick, Optechnology's director of engineering, remarked, "In
general, component materials that have very large differences in stiffness
characterize STARS and research conducted by Team UAH has shown that this attribute
offers structural engineers more design flexibility than traditional advanced
aerospace composites fabricated from materials, such as graphite or Kevlar® and
epoxy. The stiffness ratio
associated with these common composite structures is typically one hundred
whereas this ratio may be orders of magnitude higher in STARS."
According
to Team UAH's faculty advisors John Gilbert and Houssam Toutanji, "Cementitious
composites may someday replace advanced aerospace composites and we have high
hopes of using these materials to support telescopes in space, for rocket
fuselages, to build a lunar colony, or low-cost emergency shelters on
Earth. The U.S. Congress and the DoD are supporting our efforts
and Team UAH is using the U.S. Army’s state-of-the-art Remote Readiness Asset
Prognostic and Diagnostic System to quantify the dynamic characteristics of
their canoe."
According
to Jim Holeman, president of Holeman Scientific, "We're designing wireless communication links
and sensors that are specially tailored for the team's use." When asked to comment about UAH's
competition strategy Annette Wilson-Fisher, UAH ASCE Student Chapter president
and Full Spectrum project manager replied, "We tried to cover all of our bases
this year and
incorporated new developments in "STARS" technology in an effort to
enhance our boat's swimming motion."
Roy Berryman, Full
Spectrum's project engineer, commented on the boat's dynamic performance: "The first mode is anti-symmetrical
torsion and the second mode is flutter bending. When they combine as shown
in the animation, the boat acts like a fish swimming along with its paddlers to
increase their input efficiency."
Wilson added, "The
hull shapes of the winning entries at nationals are designed to satisfy
conflicting requirements and trade-offs must be made between speed, tracking,
and maneuverability. Because all of the major competitors have similar
goals, their boats have begun to look amazingly similar in shape... but
looks can be deceiving,"
Gilbert
elaborated, "Boats
of similar shape and weight are not equally efficient because their dynamic
response and modal parameters depend on the density, stiffness, and position of
the materials employed during fabrication, as well as the physical constraints
imposed by structural members and boundary conditions encountered while
racing."
Wilson and Berryman plan to elaborate
along with fellow teammates when Team UAH delivers their oral
presentation at the 2006 National Concrete Canoe Competition to be held June 15th trough
17th in Stillwater, Oklahoma.
The dynamic tuning of cementitious "STARS" is also discussed in:
Gilbert, J.A., Ooi, T.K.,
Engberg, R.C., "Modal analysis of a
lightweight concrete canoe," Concrete
Canoe Magazine, 1(1): 27-32 (2006).
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