CVG 2141 Lecture Notes - Lecture 8: Lignin, Elastic Modulus, Astm International

• School: University of Ottawa
• Department: Civil Engineering
• Course: CVG 2141
• Professor: Abdulridha Alaa

Document Summary

Controlled drying of lumber by air drying or kiln drying. Overall, mechanical properties increase (linear) as density increases. Mechanical decrease as mc increases until fsp is reached. When fsp is reached, the mechanical properties become constant (mechanical properties become independent of mc) Strongest in the longitudinal direction and weakest n the radial direction. Tension parallel to the grain is brittle with higher strength (2-4x of strength in compression ||) Compression parallel is ductile with low strength: both have linear elastic behaviour. Failure is caused by transverse rupture of cell wall. Strength can be reduced by discontinuities in the grain (knots) Perpendicular to grain: very small strength, caused by separation of cells (failure of lignin). Reduced by imperfections in wood (knots, shakes, checks) Parallel to grain has a higher strength than perpendicular (12-18% of parallel)to grain. Broom and end rolling caused by improper cutting. Valuable materials should have good bending strength and lightweight.