CIVL439/WO0D476 Wood Anatomy Cell Wall Cell Wall Structure Drink Straw Analogy -Grain direction. Species and Temperature -Load Duration Directional Elastic Properties of Wood E:E:E,s20:16:1 GuR:Gur:Gar=10:9.4:1 E:G=14:1 8 CIVL439/WOOD476 8 Wood Anatomy Cell Wall Cell Wall Layer Thickness Percentage Orientation angle to the longitudinal axis P 5% Random S 9% 50° t 70° Cell Wall Structure S1 9% 50° to 70° S2 85% 10° to 30° S3 1% 60° to 90° Drink Straw Analogy • Wood is an anisotropic material with its mechanical properties dependent – Grain direction. –Species – Moisture and Temperature – Size – Load Duration Directional Elastic Properties of Wood EL : ER : ET ≈ 20 : 1.6 : 1 GLR : GLT : GRT ≈ 10 : 9.4 : 1 EL : GLR ≈ 14 : 1 Moisture Effects on Clear Wood Strengths 30 40 50 60 70 ve Strength (MPa) ×100% − = Oven dried Weight of Wood Weight of Waterin Wood MC 0 10 20 0 20 40 60 80 100 120 MC (%) Compressiv