Characterization Methods for Elastic Properties of Wood Fibers from Mats for Composite Materials


  • R. Cristian Neagu
  • E. Kristofer Gamstedt
  • Mikael Lindström


Wood fiber, stiffness, fiber mat, test methods, composites


Wood fibers offer excellent specific properties at low cost and are of interest as reinforcement in composites. This work compares two alternative test methods to determine the stiffness of wood fibers from simple macroscopic tests on fiber mats. One method is compression of the fiber mat in the thickness direction, which uses a statistical micromechanical model based on first-order beam theory to describe the deformation. The other method is tensile testing of fiber mats and back calculation of the fiber stiffness with a laminate model. Experiments include compression tests and tensile stiffness index tests as well as determination of fiber content, orientation, and dimensional distribution. For mats with unbleached softwood kraft fibers, an effective value of the Young's modulus of 20.1 GPa determined by the compression method can be compared with values of 17.4-19.0 GPa obtained from tensile tests. These are in agreement with values for similar cellulosic fibers found in literature. The compression method is more appropriate for low-density fiber mats, while the tensile test works better for well-consolidated high-density fiber mats. The two methods have different ranges of applicability and are complementary to one another. Limitations of the methods are also discussed. The main advantage of the methods is that they are quantitative. The potential as stiffening reinforcement of various types of fibers can be systematically investigated, even if the fiber mat microstructures are different.


Alkhagen, M. I. 2002. Nonlinear elasticity of fiber masses. Doctoral Thesis, Department of Applied Mechanics, Chalmers University of Technology, Göteborg, Sweden.nAntoine, C., P. Nygård, Ø. W. Gregersen, R. Holmstad, T. Weitkamp, and C. Rau. 2002. 3D images of paper obtained by phase-contrast X-ray microtomography: Image quality and binarisation. Nucl. Instrum. Meth. A490(1-2):392-402.nBergander, A., and L. Salmén. 2000. The transverse elastic modulus of the native wood fibre wall. J. Pulp Pap. Sci.26(6):234-238.nBury, K. 1998. Statistical distributions in engineering. Cambridge University Press, Cambridge, UK. 362 pp.nCichocki Jr., F. R., and J. L. Thomason. 2002. Thermoelastic anisotropy of a natural fiber. Compos. Sci. Technol.62(5):669-678.nCox, H. L. 1952. The elasticity and strength of paper and other fibrous materials. Br. J. Appl. Phys.3:72-79.nEhrnrooth, E. M. L., and P. Kolseth. 1984. The tensile testing of single wood pulp fibers in air and in water. Wood Fiber Sci.16(4):549-566.nFellers, C., H. Andersson, and H. Hollmark. 1986. The definition measurement of thickness and density, Pages 151-167 in J. A. Bristow, and P. Kolseth, eds. Paper Structure and Properties. Marcel Dekker, New York, NY.nGamstedt, E. K., E. Sjöholm, C. Neagu, F. Berthold, and M. Lindström. 2002. Effects of fibre bleaching and earlywood-latewood fractions on tensile properties of wood-fibre reinforced vinyl ester. Pages 185-196 in H. Lilholt, B. Madsen, H. L. Toftegaard, E. Cendre, M. Megnis, L. P. Mikkelsen, and B. F. Sørensen, eds. Proc. 23rd Risø International Symposium on Sustainable and Natural Polymeric Composites—Science and Technology, Risø National Laboratory, Denmark.nHaygreen, J. G., and J. L. Bowyer. 1982. Forest products and wood science. The Iowa State University Press, Ames, Iowa, IA. 495 pp.nJaklic, A., and F. Solina. 2003. Moments of superellipsoids and their application to range image registration. IEEE T. Syst. Man Cy. B33(4):648-657.nJones, R. L. 1963. The effect of fiber structural properties on compression response of fiber beds. TAPPI46(1):20-28.nKajanto, I., J. Laamanen, and M. Kainulainen. 1998. Paper bulk and surface, Pages 89-115 in K. Niskanen, ed. Paper Physics. Fapet Oy, Helsinki, Finland.nKeckes, J., I. Burgert, K. Fruhmann, M. Muller, K. Kolln, M. Hamilton, M. Burghammer, S. V. Roth, S. Stanzl-Tschegg, and P. Fratzl. 2003. Cell-wall recovery after irreversible deformation of wood. Nat. Mater.2(12):810-814.nKomori, T., and K. Makishima. 1977. Number of fiber-to-fiber contacts in general fiber assemblies. Text. Res. J.47(1):13-17.nLeopold, B. 1966. Effect of pulp processing on individual fibre strength. TAPPI49(7):315-318.nLu, W., and L. A. Carlsson. 1996. Micro-model of paper. Part 2: Statistical analysis of the paper structure. TAPPI79(1):203-210.nLu, W., L. A. Carlsson., and Y. Andersson. 1995. Micro-model of paper. Part 1: Bounds on elastic properties. TAPPI78(12):155-164.nLu, W., L. A. Carlsson., and A. De Ruvo. 1996. Micro-model of paper. Part 3: Mosaic model. TAPPI79(2):197-205.nLundquist, L., F. Willi, Y. Leterrier, and J.-A. E. Månson. 2004. Compression behavior of pulp fiber networks. Polym. Eng. Sci.44(1):45-55.nMadsen, B., and H. Lilholt. 2002. Compaction of plant fibre assemblies in relation to composite fabrication. Pages 239-250 in H. Lilholt, B. Madsen, H. L. Toftegaard, E. Cendre, M. Megnis, L. P. Mikkelsen, and B. F. Sørensen, eds. Proc. 23rd Risø International Symposium, Risø, Denmark.nMoss, P. A., E. Retulainen, H. Paulapuro, and P. Aaltonen. 1993. Taking a new look at pulp and paper: Applications of confocal laser scanning microscopy (CLSM) to pulp and paper research. Pap. Puu-Pap. Tim.75(1-2): 74-79.nNeagu, R. C., E. K. Gamstedt, and M. Lindström. 2005. Influence of wood-fibre hygroexpansion on the dimensional instability of fibre mats and composites. Compos. Part A-Appl. S.36(6):772-788. (In press).nNordin, L.-O. 2004. Wood fiber composites: From processing and structure to mechanical performance. Doctoral Thesis, Department of Applied Physics and Mechanical Engineering, Luleå University of Technology, Luleå, Sweden.nPage, D. H., and R. S. Seth. 1980. The elastic modulus of paper II. The importance of fiber modulus, bonding, and fiber length. TAPPI63(6):113-116.nPage, D. H., F. El-Hosseiny, and K. Winkler. 1971. Behaviour of single wood fibres under axial tensile strain. Nature229(5282):252-253.nPage, D. H., F. El-Hosseiny, K. Winkler, and A. P. S. Lancaster. 1977. Elastic modulus of single wood pulp fibres. TAPPI60(4):114-117.nProvatas, N., and T. Uesaka. 2003. Modelling paper structure and paper-press interactions. J. Pulp Pap. Sci.29(10): 332-340.nReme, P. A., P. O. Johnsen, and T. Helle. 1999. Changes induced in early- and latewood fibres by mechanical pulp refining. Nord. Pulp Paper Res.14(3):256-262.nSampson, W. W. 2003. The statistical geometry of fractional contact area in random fibre networks. J. Pulp Pap. Sci.29(12):412-416.nSchulgasser, K., and D. H. Page. 1988. The influence of transverse fibre properties on the in-plane elastic behaviour of paper. Compos. Sci. Technol.32(4):279-292.nServais, C., V. Michaud, and J.-A. E. Månson. 2001. The packing stress of impregnated fiber mats. Polym. Comp.22(2):298-311.nToll, S. 1993. Note: On the tube model for fiber suspensions. J. Rheol.37(1):123-125.nToll, S. 1998. Packing mechanics of fiber reinforcement. Polym. Eng. Sci.38(8):1337-1350.nToll, S., and J.-A. E. Månson. 1995. Elastic compression of a fiber network. J. Appl. Mech.-T. ASME62(1):223-226.nTsai, S. W., and H. T. Hahn. 1980. Introduction to Composite Materials. Technomic Publishing, Westport, CT.nUesaka, T. 2002. Dimensional stability and environmental effects on paper properties, Pages 115-171 in R. E. Mark, ed. Handbook of Physical and Mechanical Testing of Paper and Paperboard. Marcel Dekker, New York, NY.nZhu, S., H. Pelton, and K. Collver. 1995. Mechanistic modelling of fluid permeation through compressible fibre beds. Chem. Eng. Sci.50(22):3557-3572.n






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