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Mechanical Characterization of Particulate Filled Vinyl-Ester Composite Steven Taylor The University of Tulsa Under the direction of: Dr. Michael A. DeBolt, Ford Motor Company Dr. John M. Henshaw, the University of Tulsa

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Overview Introduction / Background Materials and Molding Process –Calcium Carbonate –Hollow Glass Spheres –Polymeric Microspheres Modeling and Analysis –Theoretical Models –Semi-Empirical Models –Finite Element Analysis Testing Results –Mechanical Testing –Microstructure and Fracture Surface Analysis Summary and Conclusions

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Introduction Sheet Molding Compound (SMC) –Used in a variety of applications –Automotive Industry Structural components Body Panel –Composite Base Resin Filler Fiber reinforcement –Advantages Cost effective Light weight Formability Applied Composites Corp www.Hostdub.com Lorenz Kunststofftechnik GmbH

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Introduction Fillers –Traditionally Calcium Carbonate (CaCO 3 ) Inexpensive (ρ = 2.74 g/ cm 3 ) –Lightweight Filler Hollow Glass Spheres (ρ ≈ 0.3 g/ cm 3 ) Polymeric Micro spheres (ρ ≈ 0.13 g/ cm 3 )

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Background Literature search on lightweight filled materials Models which predict material properties of filled resin systems Tests and procedures used to qualify new materials Results and conclusions found in previous work

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Background Specific Properties and Fracture Toughness of Syntactic Foam: Effect of Foam Microstructures Wouterson, Boey, Hu, Wong –Epicote 1006 epoxy resin system –3M glass bubbles K 15 and K46 and Phenoset BJO-093 as filler –Mechanical test data were normalized and presented as specific mechanical and fracture properties –An increase in specific tensile strength and decrease in flexural strength with larger volume percents –Plastic deformation of the epoxy and debonding of microspheres

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Background On the Modulus of Three-Component Particulate-Filled Composites Dickie –Polymethyl methacrylate (PMMA) –Glass beads and dispersed rubber as filler –Performed tensile test to determine the modulus of the material –Kerner model was an inappropriate fit for modulus –Modulus may be dependent on size distribution, filler particle deformability and filler to matrix modulus ratios

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Background Two-Step Approach to Prediction of Asphalt Concrete Modulus from Two-Phase Micromechanical Models Li, Metcalf –Several material models to predict the modulus of asphalt concrete –Rule of mixtures, Hirsh, Hashin composite spheres, and Christensen Lo models –Young’s modulus, Poisson’s ratio, and volume fractions all had known material properties –Assumed isotropic material –Christensen Lo models gave reasonable predictions –Differences could be attributed to large sized aggregate and bond strength between the filler and binder.

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Background Elastic Modulus of Two-Phase Materials Hsieh, Tuan –Aluminum oxide containing 0 to 100% volume percentage of nickel aluminide –Compared 12 different theoretical models to experimental results –Reuss and Hashin-Shtrikman lower bond equations gave the best predications of modulus out of 12 models

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Problem Statement Compare lightweight filler to traditional filler in absence of fiber reinforcement Determine the ‘effective modulus’ of light weight filler Find effects of incremental amount of filler on material properties such as density, shrinkage, tensile and flexural strength, and thermal expansion Determine which material models most accurately predict material trends

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Materials and Molding Process Introduction & Background Materials & Molding Process Modeling & Analysis Testing Results Summary & Conclusions

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Materials and Molding Process Base Resin –Ashland Arotech Q6055 resin –Luperox DDM-9 catalyst –Westdry Cobalt 6% and Aldrich N, N-Dimethylaniline Fillers –Calcium Carbonate –Hollow Glass spheres –Polymeric microspheres

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Materials and Molding Process Molding Apparatus 1 Compressed Air Line 2 Pressure Pot 3 Resin Flow Valve 4 Resin Inlet Tube 5 Resin Inlet Tube Clamp 6 Mold Surface 7 Resin Out / Vacuum Tube 8 Resin Out Tube Clamp 9 Mold Heaters 4 6 1 3 8 2 5 7 9

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Modeling and Analysis Introduction & Background Materials & Molding Process Modeling & Analysis Testing Results Summary & Conclusions

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Material Modeling Modeling to predict material properties –Reduces costly experiments –Allows faster development of new materials Theoretical and Empirical Models –Rule of Mixtures Parallel and Series –Reuss Model –Voigt Model –Halphin-Tsai –Hashin-Strikman Bounds –Kerner Model –Paul Model –Differenital Effective Medium Theory Finite Element Analysis (FEA) –ANSYS and ABAQUS

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Material Modeling Base Resin Filler Base Resin Filler Series Model Parallel Model

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Material Modeling Reuss Model Voigt Model

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Material Modeling Hashin-Strikman Bounds

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Material Modeling Halphin-Tsai

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Kerner Model Paul Model

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Material Modeling Differential Effective Medium Theory

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Material Modeling Results Paul, Kerner and Hashin-Strikman lower Bounds models most accurately predicts the modulus of plaques containing calcium carbonate Parallel model best fits density, tensile and flexural UTS, and thermal expansion test data

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Material Models Finite Element Analysis Modeled one-quarter of the cross section of a unit cell. Set the properties of the matrix equal that of the vinyl-ester resin Created a thin walled shell and ‘glued’ the surfaces of the shell to the resin Substituted the hollow glass sphere of the hollow sphere with a solid spherical particle with unknown mechanical properties

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Material Models Finite Element Results Control Stress Contour PlotControl Strain Contour Plot

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Material Models Finite Element Results Control Stress Contour Plot ∞ 3X

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Material Models Finite Element Results 3M-S22 Axisymmetric Stress Contour Plot 2D Simplified Stress Contour Plot

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Material Models Finite Element Results 3M-S22 Axisymmetric Strain Contour Plot 2D Simplified Strain Contour Plot

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Material Models Finite Element Results Glass Spheres will carry most of the load around the air pocket with “perfect” bond strength. The resin has the greatest strains at 45° from direction of applied load. High stress concentration for polymeric microspheres. Unable to find an ‘effective’ modulus and Poisson's ratio.

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Introduction & Background Materials & Molding Process Modeling & Analysis Testing Results Summary & Conclusions Percent Shrinkage Density Tensile Flexural Microstructure Analysis Fracture Surface Analysis Testing Results

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Percent Shrinkage Measured test plaques as molded than took additional measurements after post cure Insignificant changes between as molded and post cured results

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Percent Shrinkage ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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Percent Shrinkage ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres

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Percent Shrinkage ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, O 3M-K37 & ▲ 3M-K46 Hollow Glass Spheres

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Percent Shrinkage ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Hollow Polymeric Spheres

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Percent Shrinkage Large amount of scatter –Inaccurate measuring techniques Decreasing trend in maximum percent shrinkage with increase in volume percent Insignificant changes between as molded and post cured results

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Density Test Apparatus Test performed per ASTM 792-00 1. Weighing pan of Mettler Toledo balance 2. Bracket attached to weighing pan 3. Bracket to pan attachment screws 4. Beaker Bridge 5. 250ml Beaker 6. Sinker and test specimen 7. Sinker and test specimen holder 8. Thermometer

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Density ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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Density ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres

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Density ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, O 3M-K37 & ▲ 3M-K46 Hollow Glass Spheres

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Density ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres

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Density Test Results Small amount of scatter Parallel model best predicted test results –Linear Increase in density with increase in calcium carbonate –Linear decrease in density with increase in leightweight filler

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Uni-axial Tensile Test Results Young’s Modulus –Compared results with theoretical material models. Ultimate Tensile Stress Maximum Strain to Failure Testing performed in accordance with ASTM D638 80 mm 13 mm 20 mm 45 mm 3.3 mm 12.7 mm 23 mm

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Tensile Test Results Young’s Modulus ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate Parallel Paul Series Hashin-Shtrikman Kerner

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Tensile Test Results Young’s Modulus ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres Kerner Paul Hashin-Shtrikman Series Parallel

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Tensile Test Results Young’s Modulus ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, O 3M-K37 & ▲ 3M-K46 Hollow Glass Spheres Paul Hashin-Shtrikman Series Parallel

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Tensile Test Results Young’s Modulus ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres Kerner Paul Hashin-Shtrikman Series Parallel

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Tensile Test Results Ultimate Tensile Strength ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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Tensile Test Results Ultimate Tensile Strength ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres

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Tensile Test Results Ultimate Tensile Strength ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, O 3M-K37 & ▲ 3M-K46 Hollow Glass Spheres

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Tensile Test Results Ultimate Tensile Strength ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres

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Tensile Test Results Maximum Strain to Failure ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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Tensile Test Results Maximum Strain to Failure ▲Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres

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Tensile Test Results Maximum Strain to Failure ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, ● 3M-K37 & ▲ 3M-K37 Hollow Glass Spheres

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Tensile Test Results Maximum Strain to Failure ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres

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Tensile Test Results Paul and Kerner model best predicts the modulus of palques containing calcium carbonate The ‘effective modulus’ of both the hollow glass and polymeric microspheres is equal to ~3450 Mpa Ultimate tensile strength is independent of filler type and had a linear decrease with increased filler percentage Decrease in maximum strain to failure with larger volume percents of filler Insignificant differences between 4 different series of hollow glass spheres

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Flexural Test Results Flexural Modulus Flexural Strength Maximum Flexural Strain to Failure Test performed in accordance to ASTM 6272- 02 Specimen Size of 80mm X 13mm X 3mm P TEST SPECIMEN

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Flexural Test Results Flexural Modulus ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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Flexural Test Results Flexural Modulus ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres

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Flexural Test Results Flexural Modulus ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, ● 3M-K37 & ▲ 3M-K37 Hollow Glass Spheres

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Flexural Test Results Flexural Modulus ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres

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Flexural Test Results Ultimate Flexural Stress ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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Flexural Test Results Ultimate Flexural Stress ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres

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Flexural Test Results Ultimate Flexural Stress ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, ● 3M-K37 & ▲ 3M-K37 Hollow Glass Spheres

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Flexural Test Results Ultimate Flexural Stress ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres

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Flexural Test Results Ultimate Flexural Strain to Failure ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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Flexural Test Results Ultimate Flexural Strain to Failure ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres

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Flexural Test Results Ultimate Flexural Strain to Failure ▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, ● 3M-K37 & ▲ 3M-K37 Hollow Glass Spheres

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Flexural Test Results Ultimate Flexural Strain to Failure ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres

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Coefficient of Thermal Expansion Coefficient of Linear Thermal Expansion –30°C to 150°C –Ramp 0.5°C / min –50.0 mm rod of NIST standard fused silica 739 –Test Specimens 50 mm X 8 mm X 3 mm

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CLTE Test Results ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate

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▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ■ 3M-S32 Hollow Glass Spheres CLTE Test Results

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▲Neat Vinyl-Ester Resin, ● 3M-S22, ■ 3M-S32, ● 3M-K37 & ▲ 3M-K46 Hollow Glass Spheres

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CLTE Test Results ▲ Neat Vinyl-Ester Resin ♦ Calcium Carbonate ♦ Polymeric Microspheres

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Thermal Expansion Test Results Model hollow glass particulate filler as solid particulate filler with same value for thermal expansion Parallel model does good job in predicting downward trend of test data

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Microstructure Analysis Conducted microstructure analysis to see distribution of spheres Used Image-J software to get an approximate value of volume percent filler for samples containing polymeric micropsheres SEM images to determine failure mode Fracture surface of 40 percent filler for each material.

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Microstructure Analysis 10% Filler Hollow Glass Spheres Calcium Carbonate Polymeric Microspheres No Image Available

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Microstructure Analysis 20% Filler Hollow Glass Spheres Calcium Carbonate Polymeric Microspheres

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Microstructure Analysis 30% Filler Hollow Glass Spheres Calcium Carbonate Polymeric Microspheres

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Microstructure Analysis 40% Filler Hollow Glass Spheres Calcium Carbonate Polymeric Microspheres

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Microstructure Analysis 50% Filler Hollow Glass Spheres Calcium Carbonate Polymeric Microspheres

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Fracture Surface Analysis 40% Filler By Volume Hollow Glass Spheres 40% Filler By Volume Polymeric Microspheres

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Fracture Surface Analysis 40% Filler By Volume Hollow Glass Spheres 40% Filler By Volume Polymeric Microspheres

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Microstructure Analysis Results Lack of polymeric microspheres for all volume fractions Good distribution of calcium carbonate Hollow glass spheres are grouped together at lower volume fractions Debonding between filler and matrix Small amounts of Plastic Yielding in resin

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Introduction & Background Materials & Molding Process Modeling & Analysis Testing Results Summary & Conclusions Summary and Conclusions

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The elastic modulus of resin containing calcium carbonate is higher than the resin containing lightweight filler of equal volume percentages The Paul theoretical model does best in fitting both the calcium carbonate and hollow glass and polymeric microspheres data for elastic modulus Insignificant differences between the 4 different series of 3M spheres for tensile, flexural and thermal expansion test data The effective modulus of the hollow glass and polymeric microspheres is equal to that of the vinyl ester with a value of ~3450Mpa.

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Summary and Conclusions Adding filler to the vinyl ester creates a decrease in strength of the material, which is independent of filler type. The strains to failure of the materials filled with calcium carbonate are lower than those filled with the hollow glass and polymeric microspheres with equal filler content. Scatter in percent shrinkage measurements may be caused by inadequate measuring techniques. Debonding of the resin from lightweight fillers and breakage of the spheres was observed in the failed samples.

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Recommendations Further investigation should be performed to explain the large amount of scatter in the percent shrinkage of plaques containing no filler. Further testing should be performed to fully explain the lower than expected percentage of polymeric microspheres in molded plaques for all volume fractions. Sizing effects should be investigated to create a greater bond strength between filler and resin to increase the ultimate tensile strength of the material. Expand on finite element models of lightweight to incorporate bond strength, predict compressive effects

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Acknowledgments Dr. John M. Henshaw Dr. Michael A. Debolt Dr. Winton Cornell Angela Marshall Ron Cooper Dan Houston Greg Baxter

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Questions

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