In-Plane Permeability of Oriented Strand Lumber. Part II: Microscopic Investigation of Void Structure During Compression


  • Chao Zhang
  • Gregory D. Smith


Strands, wood composites, microscopic, voids, compression, vessel, fiber


This study investigated the changes of void structure in oriented strand lumber samples pressed to different densities using microscopic techniques. Specimens of five densities, 450, 550, 625, 700, and 800 kg/m3, were examined. A method for preparing a large sectional area of wood composites for examination in a light microscope was developed. It was able to retain the original void structure and to provide high-quality images for further investigation. Microscope slides mounted with thin cross-sections for each density were prepared and then examined using fluorescence microscopy. The size and quantity of interstrand voids decreased dramatically with increasing board density. The forming and deformation of interstrand and intrastrand (ie cell lumens) voids, including failure of cell walls and nonhomogeneous collapse of cells, were observed. Generally the vessels were compressed before fibers as a result of their difference in diameter and cell wall thickness. The variability of deformation between regions within a strand and between strands within a mat was high, due to differences in strand cutting orientation, heterogeneity of mat structure, and strand property variation created by its source in different positions on a tree stem and between trees.


Blair S, Berge P, Berryman J (1996) Using two-point correlation functions to characterize microgeometry and estimate permeabilities of sandstones and porous glass. J Geophys Res 101(B9):20359-20376.nBolton AJ, Humphrey PE (1994) The permeability of wood-based composite materials. Part 1. A review of the literature and some unpublished work. Holzforschung 48 (Suppl):95-100.nDai C, Steiner PR (1993) Compression behavior of randomlyformed wood flake mats. Wood Fiber Sci 25(4):349-358.nDai C, Yu C, Zhou X (2005) Heat and mass transfer in wood composite panels during hot pressing: Part II. Modeling void formation and mat permeability. Wood Fiber Sci 37(2):242-257.nFlannery BP, Deckman HW, Roberge WG, D'Amico KL (1987) Three-dimensional X-ray microtomography. Science 237(4821):1439-1444.nGeimer RL, Mahoney RJ, Loehnertz SP, Meyer RW (1985) Influence of processing-induced damage on strength of flakes and flakeboards. Paper 463. USDA Forest Products Laboratory, Madison, WI. 15 pp.nJana D (2006) Sample preparation techniques in petrographic examination of construction materials: A state of the art review. Pages 23-70 in Proc 28th Conference on Cement Microscopy, 30 April-4 May 2006, Denver, CO.nKostiainen K, Kaakinen S, Warsta E, Kubiske ME, Nelson ND, Sober J, Karnosky DF, Saranpaa P, Vapaavuori E (2008) Wood properties of trembling aspen and paper birch after 5 years of exposure to elevated concentrations of CO2 and CO3. Tree Physiol 28(5):805-813.nKultikova EV (1999) Structure and properties relationships of densified wood. MS thesis, Virginia Polytechnic Institute and State University, Blacksburg, VA. 136 pp.nLu S, Landis E, Keane D (2006) X-ray microtomographic studies of pore structure and permeability in Portland cement concrete. Mater Struct 39(6):611-620.nMüller U, Gindl W, Teischinger A (2003) Effects of cell anatomy on the plastic and elastic behavior of different wood species loaded perpendicular to grain. IAWA J 24(2): 117-128.nPanshin AJ, de Zeeuw C (1980) Textbook of wood technology. McGraw-Hill, New York, NY. 722 pp.nSchaap MG, Lebron I (2001) Using microscope observations of thin sections to estimate soil permeability with the Kozeny-Carman equation. J Hydrol 251(3-4): 186-201.nSiau JF (1995) Wood: Influence of moisture on physical properties. Dept. of Wood Science and Forest Products, Virginia Polytechnic Institute and State University, Blacksburg, VA. 227 pp.nSugimori M, Lam F (1999) Macro-void distribution analysis in strand-based wood composites using an X-ray computer tomography technique. J Wood Sci 45(3): 254-257.nTabarsa T, Chui YH (2000) Stress-strain response of wood under radial compression. Part I. Test method and influences of cellular properties. Wood Fiber Sci 32(2): 144-152.nTabarsa T, Chui YH (2001) Characterizing microscopic behavior of wood under transverse compression. Part II. Effect of species and loading direction. Wood Fiber Sci 33(2):223-232.nWood Handbook (1999) Wood as an engineering material. Gen Tech Rep FPL-GTR-113. USDA Forest Products Laboratory, Madison, WI. 463 pp.nZhang B, Wu Q, Wang L, Han G (2005) Characterization of internal void structure of strand-based wood composites using X-ray tomography and digital tools. Pages 1-5 in Proc McMat2005—The 2005 joint ASME/ASCE/SES Conference on Mechanics and Materials, 1-3 June 2005, Baton Rouge, LA.nZhang C (2009) Measurement and modeling of the in-plane permeability of oriented strand-based wood composites. MSc Thesis, University of British Columbia, Vancouver, BC. 89 pp.nZhang C, Smith GD (2010) In-plane permeability of oriented strand lumber Part I: The effects of mat density and flow direction. Wood Fiber Sci 42(1):99-106.n






Research Contributions