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Session 29 ic2011 schwarzkopf
The document discusses techniques for measuring the tensile properties of individual wood flour particles embedded in a polymer matrix. Specifically, it examines applying short fiber composite theory to wood-plastic composites. The key points covered include: 1) Preparing wood-plastic composite samples with wood flour particles and measuring their strain distribution using optical methods and modeling. 2) Comparing the strain measurements around embedded particles to predictions from short fiber composite theory and morphology-based material point modeling. 3) Troubleshooting challenges with the optical strain measurements, such as apparent negative strains, and exploring using 3D digital image correlation to directly measure strain on individual wood particles.
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Session 29 ic2011 schwarzkopf
- 1. Tensile Properties ofIndividual Wood Flour Particles Department of Wood Science and Engineering
- 2. Introduction Wood Plastic Composites Composition: oWood Particles oThermoplastics oPS, PE, HDPE, PP, PVC oAdditives composites.wsu.edu/ navy/Navy1/materials.html Use: outdoor decking, railings, fencing, landscaping http://www.appropedia.org/File:Wood_Plastic_Composite.jpg timbers, highway infrastructure applications, etc. Known limitations: o durability o significant creep o thermo-expansion o weight/strength o… Klyosov 2008
- 3. Motivation Space forimprovement o Durability Issues o Markets Improvement strategies o Trial and Error Need more $$ Need more time o Virtual Prototyping Need better fundamental understanding – Component properties – Load transfer between components Would existing short fiber composite theory (SFCT) be sufficient to do this?
- 4. Background Short Fiber Composite Theory http://t2.gstatic.com/images?q=tbn:ANd9GcQRuVQHT1F2XZ5_l3Biw http://www.hindawi.com/journals/jnm/2010/453420/fig1/ GMSgzqaiBTXhakgfKOOtB6gB7itCUqCRZ722N11 http://urbana.mie.uc.edu/yliu/Images/short_fiber_composites.jpg Assumptions Short Fiber Theory Wood Plastic Composites Well Defined Geometry Non-Porous Well Defined Interface – Predictable Bonding
- 5. Background Short Fiber Composite Theory measured particle sizes 0.8 Measurements Particles: 0.6 A B C width, mm D 0.4 0.2 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 length, mm O’Dell (1997) Wang (2007) Hussain (2009) Assumptions Short Fiber Theory Wood Plastic Composites Well Defined Geometry Non-Porous Well Defined Interface – Predictable Bonding
- 6. Background Short Fiber Composite Theory Can we apply the theory to WPC’s? Assumptions Short Fiber Theory Wood Plastic Composites Well Defined Geometry Non-Porous Well Defined Interface – Predictable Bonding
- 7. Objectives and Approach Objectives Characterize load transfer between wood particles and the polymer matrix Verify the applicability of SFCT to WPCs Approach Measure deformation and strain distribution in and around wood particles embedded in a polymer matrix Simulate the load transfer with morphology-based material point method modeling (MPM) Compare the measurements with MPM and SFTC predictions
- 8. Strain distribution ofembedded wood particles Specimen preparation Wood flour added at a 0.25% (OD Compressed in a steel mold to the weight) loading rate thickness of ~0.6 mm Pressing temperature (150°C) Reference: 1.0 mm sections of 0.2 mm copper wire added at the same rate Compounded in Brabender Plasticoder Hot pressing @ ~150°C Unit Copper Wire - Reference Wood Particle
- 9. Strain distribution ofembedded wood particles Testing Method Stereo Microscope ε Analysis Software Stepper Motor F Field of view ~ 3 mm x 4 mm Optical resolution ~ 2 μm/ pixel Load Cell
- 10. Strain distribution ofembedded wood particles Strain Measurements – Various Angles Oriented 0° to the σ11 σ11 direction of loading Oriented 45° to the σ11 σ11 direction of loading Oriented 90° to the σ11 σ11 direction of loading
- 11. Strain distribution ofembedded wood particles Strain Measurements – Multiple Particle Interaction σ11 σ11 Various Particle-to-Particle Interactions σ11 σ11 σ11 σ11
- 12. Strain distribution ofembedded wood particles Strain Measurements - Analysis εxx 0.10 σ11 σ11 0.05 Stress-Strain Wire 0 25.00 20.00 Nominal Stress (MPa) 15.00 10.00 Exx 5.00 0.00 0.00 0.0% 2.0% 4.0% 6.0% 8.0% Strain
- 13. Strain distribution ofembedded wood particles Strain Measurements - Analysis εxx 0.10 σ11 σ11 0.05 Stress-Strain Wire 0 25.00 20.00 Nominal Stress (MPa) 15.00 10.00 Exx 5.00 0.00 0.00 0.0% 2.0% 4.0% 6.0% 8.0% Strain
- 14. Strain distribution ofembedded wood particles Strain Measurements - Analysis εxx 0.10 σ11 σ11 0.05 Stress-Strain Wire 0 25.00 20.00 Nominal Stress (MPa) 15.00 10.00 Exx 5.00 0.00 0.00 0.0% 2.0% 4.0% 6.0% 8.0% Strain
- 15. Strain distribution ofembedded wood particles Strain Measurements - Analysis εxx 0.10 σ11 σ11 0.05 Stress-Strain Wire 0 25.00 20.00 Nominal Stress (MPa) 15.00 10.00 Exx 5.00 0.00 0.00 0.0% 2.0% 4.0% 6.0% 8.0% Strain
- 16. Strain distribution ofembedded wood particles Strain Measurements - Analysis εxx 0.10 σ11 σ11 0.05 Stress-Strain Wire 0 25.00 20.00 Nominal Stress (MPa) 15.00 10.00 Exx 5.00 0.00 0.00 0.0% 2.0% 4.0% 6.0% 8.0% Strain
- 17. Strain distribution ofembedded wood particles Strain Measurements – Analysis SFCT Wire Particle Similar? Bonded Length of the Fiber Wood Particle
- 18. Strain distribution ofembedded wood particles Strain Measurements – Analysis Optical Measurement Short Fiber Theory MPM Simulation ε E σ τ 100 90 90 80 80 70 Bonded Length of the Fiber 70 60 60 50 50 40 40 30 30 20 20 10 20 40 60 80 100 120 140 20 40 60 80 100 120 140
- 19. Strain distribution ofembedded wood particles Strain Measurements – Troubleshooting Film Thickness Artifact 100 90 80 70 Optical Measurement 60 50 40 30 20 10 20 40 60 80 100 120 140 90 80 70 MPM Modeling 60 50 40 30 20 20 40 60 80 100 120 140
- 20. Strain measurement ofindividual wood particles Sample Preparation ≈ 1.0mm Adhesive ≈ 0.2mm Bridge Wood Particle Front Profile Dimensions recorded for nominal stress calculation
- 21. Strain measurement ofindividual wood particles Testing - Method F F Wood Particle Testing in Tension Optical Measurement
- 22. Strain measurement ofindividual wood particles Analysis 225.00 Stress (MPa) 150.00 75.00 (εxx) 0.00 0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7% Strain 100 80 Stress (MPa) 60 40 (εxx) 20 0 -0.5% -0.4% -0.3% -0.2% -0.1% 0.0% -20 Strain
- 23. Strain measurement ofindividual wood particles Troubleshooting 0.0006 0.0004 Apparent Negative Strain in Tension 0.0002 Strain 0 100 -0.0002 80 -0.0004 Stress (MPa) 60 Wood particle strain under no loading 40 (εxx) 20 0 -0.5% -0.4% -0.3% -0.2% -0.1% 0.0% -20 Strain Out of plane movement
- 24. Strain measurement ofindividual wood particles Troubleshooting 3D DIC Measurement Catadioptric System Wood particle Right angled Light path mirror 25 mm Planar mirror Camera 1
- 25. Strain measurement ofindividual wood particles Troubleshooting “Left” View “Right” View
- 26. Strain measurement ofindividual wood particles Troubleshooting
- 27. Conclusions Good qualitative agreementof strain patterns around the embedded particle obtained comparing: • Optical measurements • MPM modeling • Short fiber theory 3D DIC of single wood particles is possible • Single wood particle strain values can be obtained and the modulus of these particles can be determined. • Refinement of sample preparation and testing
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