Thermal Expansion Of Moist Wood
Keywords:
Betula alleghaniensis, Quercus rubra, Pscudotsuga menziesii, Sequoia sempervireus, plywood, thermal expansion coefficients, internal drying, shrinkageAbstract
Linear thermal expansion of wood, as measured with sealed cylindrical specimens at constant moisture content, generally increased with the amount of bound water. This could be expected on the basis of the low stiffness of moist wood. Near the fiber saturation point and above, shrinkage from internal drying was superimposed on true thermal expansion. At temperatures above 0 C during heating, water migrated out of fiber-saturated cell walls; the resulting shrinkage reduced the expansion significantly and between 20 and 70 C even led to contraction. At freezing temperatures during cooling, moisture diffused out of the saturated cell walls and condensed as ice crystals in the cell cavities; the resulting shrinkage supplemented true thermal contraction and caused large coefficients of thermal expansion in a broad sense.
Thermal expansion was largest tangentially and smallest in the longitudinal direction. Tangential coefficients of thermal expansion at 12% moisture content and room temperature averaged 53 X 10-1 mm/(mm C) for redwood, 70 X 10-6 mm/(mm C) for northern red oak, 38 X 10-6 mm/(mm C) for Douglas-fir and yellow birch. Coefficients in the longitudinal direction and for plywood were below 10 X 10-6 mm/(mm C) on the average.
References
Forsatth, C. C. 1946. Page 76 in L. E. Wise, Wood chemistry, 1st ed. Reinhold Publ. Corp., New York.nGlatzel, P. 1877. Neue Versuche über die Ausdehnung von Körpern durch die Wärme. Ann. Phys. Chem. 160(4):497-514.nHedlin, C. P. 1967. Sorption isotherms of twelve woods at sub-freezing temperatures. For. Prod. J. 17(12): 43-48.nHedlin, C. P. 1969. Relative humidities for Douglas-fir wood between 10 and 70 F. Wood Sci. 2(2):125-128A.nHendershot, O. P. 1924. Thermal expansion of wood. Science 60(1559):456-457.nInternational Critical Tables. 1927 and 1928. 2:469 and 4:21. McGraw-Hill, New York.nKollmann, F. P. 1968. Pages 193-194 in F. P. Kollmann and W. A. Côté, Jr., eds. Principles of wood science and technology—solid wood. Springer-Verlag, Berlin—Heidelberg—New York.nKübler, H. 1959. Längenänderungen bei der Wärmebehandlung frischen Holzes. Holz Roh-Werkst. 17(3):77-86.nKübler, H. 1962. Schwinden und Quellen des Holzes durch Kälte. Holz Roh- Werkst. 20(9):364-368.nKubler, H. 1973. Role of moisture in hygro-thermal recovery of wood. Wood Sci. 5(3): 198-204.nNikolov, S., and A. Rajčev. 1967. Thermal expansions of beech wood (in Bulgarian). Vissh Lesotekhnicheski Institut, Nauchni Trudove 14, Seria Mehanichna Tekhnologija Na D'rvesinata. Zemizdat, Sofia, p. 79-87.nOgarkova, T. V. 1961. Zavisimost' koefficienta linejnogo rasshirenija drevesiny ot ee vlazhnosti. Izv. Vyssh. Ucheb. Zaved. Lesnoj Zhurnal 4(4): 106-110.nPerkitny, T., and L. Helińska-Raczkowska. 1966. Über den Einfluss von Wachstums-spannungen auf die durch Temperatur- und Feuchtigkeitsänderung ausgelösten Verformun-gen kleiner Holzproben. Holz Roh- Werkst. 24(10):481-486.nSchirp, M., and H. Kübler. 1968. Untersuchungen über die kältebedingten Längenänderungen kleiner Holzproben. Holz Roh- Werkst. 26(9):335-341.nStevens, W. C. 1960. The thermal expansion of wood. Wood (London) 25(8):328-329.nStruve, W. 1855. Über die Ausdehnung des Eises. Fortschritte der Physik in den Jahren 1850 und 1851 6:48-52.nVillari, E. 1868. Experimental-Untersuchungen über einige Eigenschaften des mit seinen Fasern parallel oder transversal durchschnit-tenen Holzes. Ann. Phys. Chem. 133(3): 400-429.nWangaard, F. F. 1957. A new approach to the determination of fiber saturation point from mechanical tests. For. Prod. J. 7(11):410-416.nWeatherwax, R. C., and A. J. Stamm. 1946. The coefficients of thermal expansion of wood and wood products. Rep. R 1487 U.S. For. Prod. Lab., Madison.nYates, B. 1972. Thermal expansion. Plenum Press, New York—London.nYokota, T., and H. Tarkow. 1962. Changes in dimension on heating green wood. For. Prod. J. 12(1):43-45.n
Downloads
Published
Issue
Section
License
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.
