Stiffness , lumber

Figure 5.11. Mean whole-tree values of stiffness and density for hardwoods and softwoods. Superimposed is the range in values expected of lumber from Firms radiata and Eucalyptus nitens. Variations within species are greater than differences between mean values for species.

Figure 6.11. Comparison between the velocity of sound along a loblolly pine log and the mean stiffness of all lumber cut from that log (US Patent 6,006,689, 2000 filed by Weyerhaeuser).

Lindstrom H, Harris P, Sorensson CT and Evans R (2004) Stiffness and wood variation in 3-year old Pinus radiata clones. Wood Science and Technology, 38 579-97 Lindstrom T (1986) The concept and measurement of fiber swelling. In Bristow AJ and Kolsseth P (eds), Paper structure and properties. Marcel Dekker, New York, 75-97 Littleford TW (1978) Flexural properties of dimension lumber from western Canada. VP-X-179. Environment Canada, Forestry Directorate and Western Forest Products Laboratory, Vancouver, BC... 

Pressure-treated lumber has a significantly higher static coefficient of friction compared with WPCs. This is a remarkable feature of wood, along with it unsurpassable strength and stiffness compared to WPG materials. If not a relatively low durability of wood, its sensitivity to biodegradation, and an increasing scarcity of wood of a good quality, appropriate for deck materials, composite materials would hardly be competitive to real wood. 

Sparks, K. Stiff Competition Plastic Lumber Makers Shape the Market, Resource Recycling, May 1999, pp. 33-38. 

Wood composite products are conventionally manufactured from wood materials having various geometries (eg, fibers, particles, strands, flakes, veneers, and lumber) combined with a thermoset resin and bonded in a press (4). The press applies heat (if needed) and pressme to activate (cross-link) the adhesive resin and bond the wood material into a sohd panel, lumber, or beam having good mechanical (strength and stiffness) and physical (form, dimensional stabihty, etc) properties. 

---