Modeling Moisture Content-Mechanical Property Relationships For Clear Southern Pine
Keywords:Moisture content, specific gravity, clear wood, tension, bending, compression, shear, stress intensity factor, Poisson's ratio, southern pine, empirical models, dimension lumber, drying
AbstractThe objective of this study was to determine the effect of moisture content on a wide range of clear wood properties. Specimens were cut from commercially dried 38- by 140-mm (nominal 2- by 6-in.), southern pine lumber and sorted, based on specific gravity, into five matched moisture groups of approximately 40 specimens each. Empirical models are presented for predicting the effect of moisture content on strength and stiffness for the various test properties. Results indicate that tensile stress parallel- and perpendicular-to-grain and both Mode I and Mode II stress intensity factors for fracture toughness increase with decreasing moisture content from green to a peak between 7% and 13% moisture content. Upon additional drying, these properties decrease. Maximum fiber stress in bending, compression parallel- and perpendicular-to-grain, shear parallel-to-grain, and all elastic modulii increase with decreasing moisture content from green to 4% moisture content. For some of these properties, the increase is not linear at lower moisture content levels. Because specific gravity is known to affect clear wood properties, models were also developed to account for using moisture content and specific gravity. Theoretical approaches to moisture absorption that may explain experimental results are discussed.
American Society For Testing and Materials (ASTM). 1993. Annual book of standards, vol. 04.09. Standard test methods for specific gravity of wood and wood-base materials (D 2395-93). Standard methods of testing small clear specimens of timber (D 143-83). ASTM, Philadelphia, PA.nBarrett, J. D., and W. Lau. 1991. Bending strength adjustment for moisture content for structural lumber. Wood Sci. Technol. 25(6):433-447.nCaulfield, D. 1990. Effect of moisture content and temperature on the mechanical properties of paper. Pages 50-62 Proc. in Solid Mechanics Advances in Paper Related Industries, Natural Science Foundation Workshop. Aug. 13-15, 1986, Syracuse University. Syracuse, NY.nCramer, S. M., and K. A. McDonald. 1989. Predicting lumber tensile stiffness and strength with local grain angle measurements and failure analysis. Wood Fiber Sci. 21(4):393-410.nEskelsen, V., W. L. Galligan, B. Shelley, and J. Peterson. 1993. Exploring the effects of further drying on the tensile capacity of kiln-dried lumber. Forest Prod. J. 43(1):25-32.nForest Products Laboratory (FPL). 1987. Wood handbook: Wood as an engineering material. Agric. Handb. 72 (Rev.) U.S. Department of Agriculture, Washington, DC 466 pp.nGreen, D. W. 1983. In-grade testing: Impetus for change in the utilization of structural lumber. In Proc. From Stump through Mill: Recent Advancements in Spruce-Fir Utilization Technology. Aug. 17-19, 1983, University of Maine, Orono, ME.nGreen, D. W., and J. W. Evans. 1989. Moisture content and the mechanical properties of lumber: Decision for the future: Proc. In-grade Testing of Structural Lumber. June 25-29, 1988, Forest Products Laboratory, Madison, WI. Proc. 47363, Forest Products Research Society, Madison, WI.nGreen, D. W., and D. E. Kretschmann. 1994. Moisture content and the properties of clear southern pine. Res. Pap. FPL-RP-531. USDA Forest Serv. Forest Prod. Lab., Madison, WI.nGreen, D. W., R. Pellerin, J. W. Evans, and D. E. Kretschmann. 1990. Moisture content and tensile strength of Douglas fir dimension lumber. Res. Pap. FPL-RP-497. USDA Forest Serv., Forest Prod. Lab., Madison, WI.nHartley, I. D., and F. A. Kamke. 1992. Cluster theory for water sorption in wood. Wood Sci. Technol. 26:83-99.nHui, Zhou, and I. Smith. 1991. Influences of drying treatments on bending properties of plantation grown white spruce. Forest Prod. J. 41(2):8-14.nMark, R. E. 1967. Cell wall mechanics of tracheids. Yale University Press, New Haven, CT and London, UK.nNissan, A. H. 1977. Lectures on fiber science in paper, pulp and paper technology series. The Joint Textbook Committee of the Paper Industry. Canadian Pulp and Paper Association. 149. pp.nSkaar, C. 1972. Water in wood. Syracuse University Press, Syracuse, NY. 218 pp.nSPIB. 1977. Grading rules. Southern Pine Inspection Bureau, Pensacola, FL.nStamm, A. J. 1964. Wood and cellulose science. The Ronald Press Co., New York, NY. 549. pp.nWilson, T. R. C. 1932. Strength moisture relations for wood. Tech. Bull. 282. U.S. Department of Agriculture, Washington, DC.n
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