KISYI 07

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Structural Control Through Viscoelastic
Designer / Engineered Materials Harry H.
Hilton, Daniel H. Lee, Rahman A. El Fouly
Aerospace Engineering Department
(AE) National Center for Supercomputing
Applications (NCSA) Technology Research,
Education Commercialization Center (TRECC)
University of Illinois at UrbanaChampaign
Engineered Adaptive Structures VI Conference, Big
Sky, MT, July 20 - 25, 2008
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Supported by Grants from National Center for
Supercomputing Applications (NCSA) Technology
Research, Education and Commercialization Center
- ONR (TRECC) NASA Undergraduate Research
Opportunities Program (UROP) Harry H. Hilton,
Daniel H. Lee and Abdul Rahman A. El Fouly (2008)
General analysis of viscoelastic designer
functionally graded auxetic materials
engineered/tailored for specific task
performances, Mechanics of Time-Dependent
Materials 12151-178.
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OUTLINE Motivation Viscoelasticity Creep
buckling Auxetic materials Functionally graded
materials Failure probabilities Designer
materials Conclusions
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MOTIVATION 1 - The Problem How to minimize
failures, weight structural responses under
dynamic loads, thermal stresses, aero/hydro
noise, etc. 2 - A Solution Use the natural
damping properties of viscoelastic
materials 3 - Protocol Find optimum (a)
Viscoelastic designer material properties, i.
e. relaxation moduli, (b) Viscoelastic
functionally graded material (VFGM) Both
moduli VFGM are tailored / engineered to
produce favorable damping failure
probabilities
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• NEW RESULTS FOR VISCOELASTIC MATERIALS
• Integrated approach to optimum designer /
  engineered auxetic viscoelastic properties
  and distributed material
• non-homogeneities, i.e. functionally
• graded materials, for individual structural
  elements and/or the entire structure

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VISCOELASTICITY
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VISCOELASTIC MATERIALS POLYMERS, COMPOSITES,
RUBBERS, GLASS SOLID PROPELLANTS,
MATTRESSES, BONDING AGENTS ELECTRONIC CIRCUIT
BOARDS HIGH TEMPERATURE METALS CONCRETE,
ASPHALT, ROCK SALT, PAINT, ICE MOTION
SOUND DAMPERS FOOD CHEESE, PASTA, JELL-O,
etc. BIOLOGICAL GEOLOGICAL MATERIALS
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IMPORTANT MATERIAL PROPERTIES STABILITY
CONDITIONS CONSTITUTIVE RELATIONS (moduli,
relaxation creep functions) FAILURE
CRITERIA (aging, cracks, delamination,
etc.) STABILITY CRITERIA (creep buckling,
creep wing panel flutter)
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VISCOELASTIC CHARACTERISTICS TIME
DEPENDENT MEMORY ENERGY DISSIPATION
RELAXATION CREEP NO YIELD POINT
E
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• VISCOELASTIC PROBLEM DEFINITION
• MATERIALS CREEP IN TIME
• Increased applied bending moments
• Decreased moduli resisting moments
• RESULT
• Panel creep buckling creep flutter
  Instability (tcr tf)
• Large deflections ? Failure (td)
• FAILURE STRESSES DEGRADE IN TIME
• RESULT Shorter survival times (tult ?
  tcr ? tf ? td)

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M
VISCOELASTIC BEAM DEFLECTION CONTROLLED ONLY
THROUGH TEMPERATURE DEPENDENT MATERIAL
DAMPING PROPERTIES
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Control is due solely to viscoelastic material
properties. Similar action can be achieved with
piezo MR devices
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VISCOELASTIC DESIGNER MATERIALS
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Need for Designer Materials The purpose is
not to build a better mouse trap, but to
make one by analytically creating
(tailoring or engineering) materials with
appropriate properties instead of using off
the shelf items. (Manufacturing processes
of materials are not considered here.)
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DESIGNER MATERIALS For specific
conditions, (1) viscoelastic properties in the
form of relaxation/creep responses are
analytically tailored to provide best
performance in terms of failure stresses,
deformations, minimum structural weight,
survival times, cost, etc. (2) VFGM need to be
strategically placed. Harry H. Hilton and Sung
Yi (1992) Analytical formulation of optimum
material properties for viscoelastic damping,
Journal of Smart Materials and Structures,
1113-122. Cristina E. Beldica and Harry H.
Hilton (2003) Analytical simulations of optimum
anisotropic linear viscoelastic damping
properties, J. of Reinforced Plastics and
Composites, 181658-1676, 1999. Harry H. Hilton
(2003) Optimum viscoelastic designer materials
for minimizing failure probabilities during
composite cure, Journal of Thermal Stresses,
26547-557. Harry H. Hilton (2005) Optimum
linear nonlinear viscoelastic designer
functionally graded materials characterization
and analysis, Composites A Applied Science
Manufacturing,361329-1334. Harry H. Hilton and
Abdul Rahman A. El Fouly (2007) Designer auxetic
viscoelastic sandwich columns tailored to
minimize creep buckling failure probabilities and
prolong survival times, Proc. 48th
AIAA/ASME/ASCE/AHS SDM Conference,
AIAA-2007-2400.
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DESIGNER MATERIALS - SENSITIVITY ANALYSIS
Dissipative energy is most influenced by
Region C and by ratio E0 / E8
E0
E8
Harry H. Hilton and Sung Yi (1992) Analytical
formulation of optimum material properties for
viscoelastic damping, Journal of Smart Materials
and Structures, 1113-122.
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INPUT Loads geometry OUTPUT Deflections
QUESTION What material properties and
their spatial distributions are needed to
produce desired deflections?
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DESIGNER MATERIALS With direct or
inverse protocols find optimum tailored /
engineered relaxation moduli through best
combination of designer viscoelastic
material parameters VFGM(x) for
prescribed service conditions. Nijkl Eijkl(x,t)
Eijkl8(x) ? Eijkln(x) exp- t /
tijkln(x) n1
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• ROAD MAP FOR DESIGNER
• VISCOELASTIC FGM
• Create tailored non-homogeneities through
• 1. Spatial temperature gradients
• Different materials composite fibers,
• particles, nano-materials, fluid mixtures, etc.
• 3. Provide control with material damping
  piezoelectric, magnetic, SMA properties, etc.

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FUNCTIONALLY GRADED MATERIALS
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NONHOMOGENEITIES ANISOTROPY ARE DUE
TO Functionally graded materials Temperature
gradients Composite fibers Multiple dissimilar
materials Nano material inclusions Fluid
mixtures
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• ROAD MAP for DESIGNER VFGM
• Create tailored non-homogeneities through
• 1. Spatial temperature gradients
• Different materials composite fibers,
• particles, nano-materials, fluid mixtures, etc.

5-layer functionally graded ZrO2 / Ni Co Cr
AlY coating http//www.ntu.edu.sg/mae/research/pr
ogrammes/adv_materials/FGM.htm
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DESIGNER MATERIALS For specific loading
and boundary conditions 1 - Viscoelastic
properties, i.e. relaxation moduli, are
analytically tailored to provide best
performances in terms of failure
probabilities, deformations, min. weight,
survival times, etc. 2 - VFGM properties are
strategically distributed and result in
non-homogeneous materials Protocol Material
properties not structures are being designed
/ engineered.
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AUXETIC MATERIALS
Roderic S. Lakes (1987) Foam structures with a
negative Poissons ratio, Science
23510381040. E. A. Friis, Roderick S. Lakes
and J. B. Parks (1988) Negative Poissons ratio
polymeric and metallic foams, Journal of
Material Science 2344064414.
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SANDWICH COLUMN or PLATE Sandwich
construction with foam, honeycomb, rubber,
etc. cores
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AUXETIC MATERIALS ELASTIC MATERIALS Poissons
Ratio -1 ?E 0 Shear Modulus GE gtgt
Youngs Modulus EE VISCOELASTIC
MATERIALS Poissons Ratio is NOT A
CRITERION! Shear Modulus G(t) gtgt Youngs
Modulus E(t)
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Auxetic Elastic Materials

Auxetic Viscoelastic Materials

There are no other limits on viscoelastic
?ij(t) for t gt 0!
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ELASTIC MATERIALS
VISCOELASTIC MATERIALS
No integral elastic-viscoelastic
correspondence principle for Poisson ratios,
only for moduli!
Harry H. Hilton (2001) Implications and
constraints of time independent Poisson ratios in
linear isotropic and anisotropic
viscoelasticity, Journal of Elasticity,
63221-251.
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• Shtark, H. Grosbein, G. Sameach and H. H. Hilton
  (2007) An alternate protocol for determining
  visco-
• elastic material properties based on tensile
  tests without use of Poisson ratios, Proceedings
  
• International Mechanical Engineering Congress and
  Exposition. ASME Paper IMECE2007-41068. Seattle,
  WA.

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CREEP BUCKLING
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Creep buckling delamination
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DETERMINISTIC or STOCHASTIC UNIAXIAL
MULTIAXIAL FAILURE ANALYSIS H. H. Hilton and
S. T. Ariaratnam (1994) Invariant anisotropic
large deformation deterministic and stochastic
combined load failure criteria, International
Journal of Solids and Structures, 313285-3293.
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Note different experimental tension
shear delamination stresses the moisture
influence
D. A. Dillard H.F. Brinson (1983) A
numerical procedure for predicting and delayed
failures in laminated composites, Long Term
Behavior of Composites, ASTM STP813, 23-37.
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DISTINCT LOADING PATTERNS WILL RESULT
IN DIFFERENT FAILURE CONDITIONS
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WEIBULL DISTRIBUTION PROBABILITY OF
FAILURE P(u) 1 - exp-(u/ß)?
C.C. Hiel, M. Sumich D.P. Chappell (1991) A
curved beam test specimen for determining the
interlaminar tensile strength of a laminated
composite, Journal of Composite Materials,
25854-868.
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A material failure surface based on stress
invariants
DETERMINISTIC FAILURE SURFACE
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VISCOELASTIC DESIGNER MATERIALS
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Relaxation Modulus
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Viscoelastic Functionally Graded Material
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Viscoelastic Constitutive Relations
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Constraints
Constraints creep buckling, flutter, failure
probability, life time, cost, composites no.
orientation of plies
Governing Equations
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Analytical Solution Protocols Eliminate
x-dependence through Galerkin approach - leaves
algebraic relations in unknown parameters
time Collocation Least Squares Calculus of
Variations Lagrangean Multipliers Inverse Trial
Error
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Number of Unknown Parameters Each structural
element 30 1,260 material parameters 5 20
constraint parameters Entire flight vehicle
structure 50 3,000 major elements 1,750
3,840,000 unknown parameters and simultaneous
equations (With aerodynamics,
aero-viscoelasticity, morphing, stability,
control, etc. multiply by 150)
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• ISSUES
• IntegralDifferential Equations
• Evaluation of Time Integrals
• Evaluation of Material Property
• Other Unknown Parameters
• Solution on Massively Parallel HPCs such
  as NCSA-IBM Blue Waters Petascale System -
  Operational in 2011
• http//www.ncsa.uiuc.edu/BlueWaters/

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A FEW RESULTS Single
elements Creep buckling Aerodynamic noise
attenuation
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Failure Probabilities for Wing Panel Exposed
to Aerodynamic Noise
Lowest failure probabilities longest survival
times are obtained by optimizing relaxation
moduli distributing nonhomogeneous properties
in both in plan directions (green curve)
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DESIGNER MATERIALS INVESTIGATED PROBLEMS Large
deformations of beams, columns, plates
shells Aero-acoustic noise attenuation Tempera
ture, piezo-electric, MR, SM servo
controls Wing shape camber line morphing
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CONCLUSIONS (The end is near!!)
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• CONCLUSIONS
• INCREASES IN TEMPERATURE ?
• Decrease times to creep buckling
• Induce thermal stresses expansions
• Increase dissipation rates
• May stabilize or destabilize panel

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CAVEAT IN SELF EXCITED SYSTEMS (buckling,
aeroelasticity, etc.) ANY CHANGE INCLUDING
DAMPING MAY STABILIZE OR DESTABILIZE
MOTION STABILITY IS A FUNCTION OF PHASE
RELATIONS
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FUTURE PLANS INCORPORATE AERODYNAMICS, STABIL
ITY CONTROL, FLIGHT PERFORMANCE, PROPULSI
ON, ETC. IN ORDER TO ANALYZE ENTIRE
VEHICLE
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• APPLICATIONS of VISCOELASTIC
• DESIGNER MATERIALS
• Airplanes, UAVs, MAVs, missiles, space
  vehicles, satellites, deployable gossamer
  structures, antenna dishes, space suits,
  body armor, solar sails,
• circuit boards, etc.
• Ground transportation automotive,
• tanks, railroads, cargo containers
• Submarines and other navy ships

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ADDITIONAL INFORMATION VOICE 217-333-2653 /
840-1116 FAX [phone] h-hilton _at_
uiuc.edu csm.ncsa.uiuc.edu https//netfiles.uiu
c.edu/h-hilton/www/hilton.html
www.trecc.org/features/USSAshville/ THANK YOU.
QUESTIONS?