MULTI-SCALE MODELING OFSTRAND-BASED WOOD COMPOSITES        FPS 65th International Convention       June 19-21, 2011, Portl...
UBC Composites Group• 2 Departments: Civil Engineering & Materials Engineering• Group exists since the early 1980‘s• Proje...
Outline• Motivation• Multi-Scale Approach• Partial Resin Coverage• Results  – Mesoscale  – Macroscale• Conclusions        ...
Motivation• Strand-based wood composites frequently used as  construction materials in residential and other buildings• Ce...
Multi-Scale ApproachMacroscale        x3PSL beam                x2                         x1                       Strand...
Multi-Scale Approach (cont.)                             Macroscopic Element                  Unit Cell                   ...
Multi-Scale Approach (cont.)                PSL                                            Dimensions:Macroscale          ...
Multi-Scale Approach (cont.)                PSL                                  • Randomly distributing                 q...
Partial Resin CoverageWhy not a full resin coverage?• In manufacturing process of strand-based composites, strands  are no...
Partial Resin Coverage (cont.)                                     Full resin coverage                                    ...
Partial Resin Coverage (cont.)                                       Scenario A                                           ...
Partial Resin Coverage (cont.) • Introducing void elements for partial coverage   simulations   Resin                     ...
Results (Mesoscale) • Comparison with full coverage caseS23                            S23      3          2 1            ...
Results (Mesoscale)           13.00                                                                                       ...
Results (Mesoscale)• Scenario A   – For a constant resin area coverage, as the resin thickness     decreases, resin conten...
Results (Macroscale)                                                                                                      ...
Conclusions• The concept of resin area coverage has been incorporated into  the multi-scale model.• A series of codes were...
Acknowledgements• Benjamin Tressou, ENSMA, France• Dr. Carole Nadot-Martin, ENSMA, France• Sardar Malekmohammadi, UBC• Dr....
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Session 29 ic2011 gereke

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Session 29 ic2011 gereke

  1. 1. MULTI-SCALE MODELING OFSTRAND-BASED WOOD COMPOSITES FPS 65th International Convention June 19-21, 2011, Portland, OR, USAT. Gereke, S. Malekmohammadi, C. Nadot-Martin, C. Dai, F. Ellyin, and R. Vaziri CIVIL ENGINEERING AND MATERIALS ENGINEERING COMPOSITES GROUP
  2. 2. UBC Composites Group• 2 Departments: Civil Engineering & Materials Engineering• Group exists since the early 1980‘s• Projects: – Processing for Dimensional Control – Development of an Integrated Process Model for Composite Structures – Tool-part interaction - Experiments and modeling – Viscoelaticity and residual stress generation – Characterization of damage in impact of composite structures – Damage and strain-softening characterization – Observation of fracture in-situ inside an SEM: aerospace and biomaterial applications – Multi-scale modelling of wood composite products www.composites.ubc.ca 2
  3. 3. Outline• Motivation• Multi-Scale Approach• Partial Resin Coverage• Results – Mesoscale – Macroscale• Conclusions 3
  4. 4. Motivation• Strand-based wood composites frequently used as construction materials in residential and other buildings• Certain requirements on their mechanical properties such as stiffness and strength• Realistic modeling as a viable alternative to time consuming and costly experiments• Goal: development of a numerical model that can serve as a tool to control the properties of the constituents in order to optimize the macroscopic material behavior 4
  5. 5. Multi-Scale ApproachMacroscale x3PSL beam x2 x1 Strand VoidMesoscale Resin x2Resin coveredstrand x1 x3 Resin InterfaceMicroscale WoodWood cells Courtesy of Hass et al., Wood Sc Tech, 2011 5
  6. 6. Multi-Scale Approach (cont.) Macroscopic Element Unit Cell y2Macroscale y1 Wood y3PSL beam Structure q Resin Effective composite propertiesMesoscaleResin coveredstrand x2 x1 x3 Real Mesostructure Idealized Mesostructure 6
  7. 7. Multi-Scale Approach (cont.) PSL Dimensions:Macroscale X2 • X1 = 380 mmPSL beam • X2 = 39 mm + 6tR X1 x2 • X3 = 40 mm + 16tR x1 X3 x3Mesoscale Unit Cell • Y1 = 600 mm + 2tRResin covered Resin • Y2 = 13 mm + 2tR Wood Y2strand • Y3 = 5 mm + 2tR Y1 y 2 y1 Y3 y3 tR, resin thickness 7
  8. 8. Multi-Scale Approach (cont.) PSL • Randomly distributing q=0°Macroscale q=5° Load maximum grain angle (distribution accordingPSL beam q=10° q=20° to Clouston, 2007*) x2 1500 1301 Frequency x1 1000 x3 340 403 500 116 0 0 5 10 20 Maximum grain angle, q (°)Mesoscale Unit Cell • Calculation of effectiveResin covered elastic properties bystrand applying periodic boundary conditions to the unit cell y2 y1 y3 *Clouston, P., Holzforschung 61:394-399, 2007 8
  9. 9. Partial Resin CoverageWhy not a full resin coverage?• In manufacturing process of strand-based composites, strands are not fully covered by the resin.• Resin distribution should be considered in the modeling approach.• Voids are distributed randomly through a typical wood composite (PSL). 0.6 0.5 Micro- Macro- Relative frequency 0.4 voids voids 0.3 0.2 0.1 10 cm × 10 cm 0.0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 Void size (%) 9
  10. 10. Partial Resin Coverage (cont.) Full resin coverage Partial resin coverage • Linear relation between • Resin area coverage (RA) resin content (RC) and resin increases as more resin is thickness (tR) used in the manufacturing • No resin penetration process • No voids in the • No resin penetration microstructure • Two scenarios considered: 0.30 100% A. RA increases with RCResin thickness, tR (mm) Resin area coverage, RA 0.25 80% uniformly at a constant tR 0.20 60% B. Both RA and tR increase with RC (Dai’s model*) 0.15 40% 0.10 20% 0.05 0.00 0% 0% 2% 4% 6% 8% Resin content by volume, RC *Dai, C. et al., Wood and Fiber Science 39:56-70, 2007 10
  11. 11. Partial Resin Coverage (cont.) Scenario A Scenario B RA increases with RC Both, RA and tR increase uniformly at a constant tR with resin content 100% 0.30 100% 0.30 Resin thickness, tR (mm) 0.25 0.25 Resin area coverage, RA Resin thickness, tR (mm)Resin area coverage, RA 80% 80% 0.20 0.20 60% 60% 0.15 0.15 40% 40% 0.10 0.10 20% 20% 0.05 0.05 0% 0.00 0% 0.00 0% 1% 2% 3% 4% 5% 6% 7% 8% 0% 1% 2% 3% 4% 5% 6% 7% 8% Resin content by volume, RC Resin content by volume, RC Dai et al. (2007):   s RC  RA  1  exp   21  MC   R    r r solids  11
  12. 12. Partial Resin Coverage (cont.) • Introducing void elements for partial coverage simulations Resin Void elements are distributed Elements by replacing some resin elements in the original full coverage discretized FE model Wood Elements RA = 60%.Discretized FullCoverage FE model Discretized Partial Void Coverage FE model Elements 12
  13. 13. Results (Mesoscale) • Comparison with full coverage caseS23 S23 3 2 1 Full coverage Partial coverage E1 = 12.64 GPa E1 = 12.41 GPa RA = 100% RA = 60% 13
  14. 14. Results (Mesoscale) 13.00 13.00 tR variable tR variable 12.80 12.80 12.60 tR = 0.08 mm 12.60 tR = 0.08 mmE1 (GPa) E1 (GPa) 12.40 12.40 12.20 tR = 0.28 mm 12.20 tR = 0.28 mm 12.00 12.00 11.80 11.80 11.60 n=10 11.60 n=10 11.40 11.40 0% 2% 4% 6% 8% 0% 20% 40% 60% 80% 100% Resin content by volume, RC Resin area coverage, RA 100% tR variable Resin area coverage, RA 80% tR = 0.08 mm 60% tR = 0.28 mm 40% 20% Scenario A 0% Scenario B 0% 2% 4% 6% 8% Resin content by volume, RC 14
  15. 15. Results (Mesoscale)• Scenario A – For a constant resin area coverage, as the resin thickness decreases, resin content decreases while E1 increases – E1 increases with resin area coverage• Scenario B – By adding more resin, E1 increases until RA ≈ 80% then it drops, since E of the resin is lower than EL of the wood• Resin thickness and resin area coverage could significantly alter the properties of the unit cell. 15
  16. 16. Results (Macroscale) Scenario A • Prediction of bending MOE Scenario B 11 11 tR = 0.08 mm tR variable tRtR variable = 0.08 mm 10 Bending MOE (GPa) 10Bending MOE (GPa) tR = 0.28 mm tR = 0.28 mm 9 9 8 8 n=250 n=250 7 7 0% 2% 4% 6% 8% 0% 20% 40% 60% 80% 100% Resin content by volume, RC Resin area coverage, RA MOE highly depends on resin thickness and then resin area coverage as the resin thickness increases. 16
  17. 17. Conclusions• The concept of resin area coverage has been incorporated into the multi-scale model.• A series of codes were developed to distribute void elements randomly and analyze results both at meso- and macroscale.• Stochastic simulation shows that MOE could vary between 8 to 10 GPa depending on the resin thickness and resin area coverage.• Establishing a realistic relation between RC and RA could help predicting the macroscopic properties of wood composites more accurately within a large range of RC.• Incorporation of resin penetration and strand compaction will improve the model in the future (microscale) 17
  18. 18. Acknowledgements• Benjamin Tressou, ENSMA, France• Dr. Carole Nadot-Martin, ENSMA, France• Sardar Malekmohammadi, UBC• Dr. Chunping Dai, FPInnovations• Mr. Gregoire Chateauvieux and Mr. Xavier Mulet, ENSAM, France• Financial support: Natural Sciences and Engineering Research Council of Canada (NSERC) 18
  19. 19. Questions?

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