Performance and Interfacial Stresses in the Polymer Wear SurfaceFRP Deck Bond Due to Thermal Loading

1
Performance and Interfacial Stresses in the
Polymer Wear Surface/FRP Deck Bond Due to Thermal
Loading

• D.C. Haeberle, J.L. Senne, J.J. Lesko,
• and T.E. Cousins
• Materials Response Group
• Virginia Tech

2
Project Description

• Evaluation of the effects of sample variables on
  the properties of a polymer wear surface produced
  on a pultruded glass-reinforced isophthalic
  polyester surface for bridge deck applications.

Properties
Sample Variables
strain-to-failure tensile rupture puncture
resistance durability peel
resin type aggregate size distribution surface
thickness treatments to the composite surface
temperature
3
Polymer Wear Surface Construction
1. Silica or Basalt Cleaned Aggregate 2. Derakane
8084 Toughened Vinyl Ester Resin 3. Pultruded
Isophthalic Polyester/Glass Composite Surface
4
Strain-to-Failure Test

• ASTM D-790 4-point bend test
• Wear surface on the tensile side
• Strain measured with an extensometer mounted to
  wear surface
• gt0.2 strain-to-failure desired
• Tested at -40 oC, 25 oC, and 60 oC

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Strain-to-Failure Results Temperature Comparison
Bottom Layer Gap-Graded Quartz Top Layer Fine
Quartz Resin Toughened Vinyl Ester
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Vinyl Ester DMA Results

• Tg gt 60 C, maximum test temperature
• Vinyl Ester modulus decreases with increasing
  temperature, affecting the mechanics of the
  problem

7
Tensile Bond Strength Test

• VTRC standard test method
• Modified improved for Instron Testing
• 1.38 MPa (200 psi) strength desired

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Tensile Bond Strength Results
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Bending Effects from DT E1ltE2 a1gta2
Temperature Increase
Temperature Decrease
1
1
2

• Wear Surface Contraction Restricted by FRP plate
• Tensile Peel Stress At Free Edge

2

• Wear Surface Expansion Restricted by FRP plate
• Compressive Peel Stress At Free Edge

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Finite Element Analysis
Perfectly Bonded Interface

• 2-D Plain Strain Model
• Isotropic Material Properties
• No Property Temperature Dependence

Symmetry Condition
Wear Surface
Composite Substrate
Free Edge
Fixed Point
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DT -33 C Results
y
Maximum Peel Stress 1.2 MPa Wear Surface
Mechanical Strain -273 me
x
Compressive surface strains should mechanically
improve performance at lower temperatures,
opposite of experimental results
12
DT -33 C with Constrained Surface Results
y
Maximum Peel Stress 2.5 MPa Wear Surface
Mechanical Strain 179 me
x
Fixed in the y-direction
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Analytical Stress Predictions

• Elasticity
• Solution
• p(x)max at Free Edge
• t(l )0
• t(x)max is at 3.3 in
• Peel solution at h/l not stable

• Simplified Elasticity Solution
• p(x)max at Free Edge
• t(l )? 0
• t(x)max at Free Edge
• Shear stress free edge condition invalid

Shear Stress Solution
Peel Stress Solution
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Thermal Induced Stress Predictions DT -33 oC
Acetone prepared surface bond strength 690 kPa
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Experimental Work

• Gages on the FRP Plate, concentrated at the free
  edge
• Thermocouples were placed on the sample to
  determine thermal equilibrium
• Temperature Cycle 15C / -17.8C DT33C (based
  on ASTM C666)

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Thermally Induced Mechanical Strain
Results/Prediction
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Conclusions

• The temperature dependence of the
  strain-to-failure results is not dominated by the
  mechanics associated with thermally induced
  stresses from the bi-material bond, but more
  likely dominated by changes in fracture behavior
  and thermal effects in the particulate composite
• The closed form solution provides reasonable
  results as compared to the finite element
  solution, but evaluation of this method must be
  further evaluated and confirmed
• The analytical approach is a great tool for
  quickly determining the effects of changes in
  modulus and geometry of the system on thermally
  induced stresses and strains
• Residual stresses do exist and any reduction in
  these stresses is a benefit for the system

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Future Work and Recommendations

• Utilize the analytical solution to evaluate the
  stresses and strains in the wear surface under
  the constrained condition
• Expand solutions to include temperature dependent
  properties
• Include wear surface in bridge deck finite
  element model to predict the effects of combined
  thermal and mechanical loading
• Peel stresses are significant, and therefore,
  adequate surface preparation to the bridge deck
  must be applied to prevent low tensile bond
  strength, such as those seen with the acetone
  washed surface

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Acknowledgements

• Virginia Transportation Research Council
• Strongwell Corporation
• Landford Brothers Contractors
• Dow Chemical
• Materials Response Group
• Center for Adhesive and Sealant Science (CASS)
• Adhesive and Sealant Council Education Foundation