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The hot pressing process of oriented strand board:

Review of the modeling. The hot pressing process of oriented strand board:. Dr. Azzeddine OUDJEHANE. "Everything should be as simple as possible, but not simpler.". 2. Flakes are dried Adhesive applied. 3. Mats are formed. 5. Panels are trimmed to the final sizes.

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The hot pressing process of oriented strand board:

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  1. Review of the modeling. The hot pressing process of oriented strand board: Dr. Azzeddine OUDJEHANE

  2. "Everything should be as simple as possible, but not simpler."

  3. 2. Flakes are dried Adhesive applied 3. Mats are formed 5. Panels are trimmed to the final sizes 4. Mats are hot-pressed T=200oC Manufacturing process 1. Logs are flaked

  4. Hot pressing of wood mats Continuous press Multiple openings platen press

  5. Continuous press Cross section of a continuous press (H Thoemen 2000)

  6. Hot-pressing mechanisms • Rheology and mechanics Deformation under applied pressure • Thermodynamics Heat and mass transfer • Adhesion Resin cure

  7. Background review (1) • Modeling the continuous pressing process for wood based composites, by H. Thomen et al @ OSU

  8. Burger-Humphrey model used by H. Thomen et al for the continuous hot-pressing

  9. Background review (2) • A global model for the hot pressing of MDF, by Costa et al @ Porto U.

  10. Background review (3) • Viscoelastic behavior of wood fibers during the hot pressing of MDF, by J. Van Houts et al @ Auckland U.

  11. Background review (4) • Effect of panel moisture content and density on moisture movement, by A.Cloutier et al @ Laval U.

  12. Background review (5) • OSB preparation technology at high moisture content: Transfer mechanisms and pressing parameters, by A. Pizzi et al ENSTIB-HH U.- Siempelkamp

  13. Background review (6) • Hot pressing of OSB by step closure, by S.Wang, P.Winnistorfer et al @ UTK

  14. Density profile and consolidation during pressing by Siqun Wang et al

  15. Background review (7) • Simulation of the internal conditions during the hot pressing process, by Z. Ballazs, F. Kamke et al @ VTU

  16. Background review (8) • Mat formation and pressing models, by P.Hubert, C.Dai et al @ FORINTEK

  17. Flow chart for the model component with FEM solver, by P.Hubert et al Forintek

  18. Background review (9) • 3D heat and mass transfer during OSB hot pressing, by P. Garcia et al @ UBC

  19. Background review (10) • A continuum model of the interaction between manufacturing variables and consolidation of wood composite mats, by A. Oudjehane et al @ UBC

  20. Structure model Consolidation model Mechanical model Framework of Analysis Loose mat analysis End-product analysis

  21. Consolidation tensor C such that: in the mat / panel. in any location of the mat / panel. History of Deformation • accounts for the deformation process = consolidationof the mat into a panel ho hp a

  22. Forming process variables Raw material properties Hot-pressing parameters Panel density Strands’ thickness and density Density = F Number of deposited strands Panel thickness, mass transfer flux Panel consolidation Strands’ thickness and density tr C = F Number of deposited strands Panel thickness, mass transfer flux Properties of composite panels

  23. Stiffness - Compliance F (trC, q) oriented layout F (trC, q) oriented layout MOE = MOR= F (trC) randomly oriented layout F (trC) randomly oriented layout Strength Internal bond IB (internal Bond) = F (trC) Dimensional stability TS (thickness swell) = F (trC) Properties of composite panels

  24. tp ho a Consolidation Model • define the history of deformation induced by the manufacturing process.

  25. tp h1 ho a a tp= panel thickness h1=Nf.tf a Consolidation Model • define the deformation induced by the manufacturing process in any location of the mat. Consolidation = Elimination of voids + Compression of flakes With heat and mass transfer m(z)=mass transfer flux = function of moisture content CR= compression ratio=panel thickness/strand thickness

  26. Press closing Press opening mat initial thickness Press relaxation panel thickness t1 t2 t3 Consolidation Model Position control press Platen position Time

  27. Strain Pressure Time Time t1 t1 Constitutive Equation Strain rate Time s(t) = K . t (U(t) Stress = F (strain, strain rate) e (t) = ev + e c t1 Consolidation Model Hot-Press Closing

  28. h s s ss e 0 E L,N Viscoelastic strain ev Viscoplastic strain ec Rheological Model • Non-linear viscoelastic and viscoplastic

  29. Model vs. Experience Visco-elastic plastic with creep consolidation model by A.Oudjehane et al 1998

  30. Consolidation Model Hot-Press Relaxation Strain Time Pressure t1 t2 Time t1 t2 Constitutive Equation Strain = cte. Stress = F(Strain, Strain rate)

  31. Next step • Implement the heat and mass transfer into the consolidation model

  32. Forming process On-line measurement Hot-pressing On-line measurement Towards on-line evaluation of OSB Flaking Drying Blending Strands properties Moisture content Resin content Mat layout Mat thickness Panel thickness Pressing conditions Software MOE, MOR, Density TS, IB

  33. Je crois ce que je vois, Je vois ce que je regarde, et je regarde ce que je veux.Blaise Pascal I believe what I see, I see what I look at, I look at what I want.

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