Measuring Shear Moduli in Wood with Small Tension and Compression Samples


  • Wenjie Zhang
  • Alan Sliker


Shear modulus, modulus of rigidity, wood, tension test, compression test


Shear moduli in wood were measured on tension and compression specimens by means of rosettes of specially made bonded resistance strain gages. Angle α between the load axis and the longitudinal, L, direction for matched specimens were 10, 20, and 45 degrees. Better results were achieved with the tension specimens than with the compression specimens probably because of end restraint of the compression specimens. Although there were only small differences among shear moduli measured at angles α of 10, 20, and 45 degrees, the 20-degree specimens usually had shear moduli values that were closest to those from plate specimens. The maximum strain in each test specimen was not parallel to the load axis: for most specimens it was calculated by strain gage rosette analysis to be at an angle between 20 and 30 degrees to the load axis. Although instrumentation with strain gages is time-consuming, the specimens are easier to cut accurately from wood than are the plate specimens that are sometimes used.


American Society for Testing and Materials. 1989 (also 1978). Standard method of test for shear modulus of wood. ASTM D 3044-76, Philadelphia, PA.nEbrahimi, G. 1979. Measuring Young's moduli, shear moduli, and Poisson's ratios for wood by a tension test. Ph.D. thesis, Dept. of Forestry, Michigan State Univ., E. Lansing, MI.nEbrahimi, G., and A. Sliker. 1981. Measurement of shear modulus in wood by a tension test. Wood Science 13(3):171-176.nGreszczuk, L. B. 1966. New test technique for shear modulus and other elastic constants of filamentary composites. Douglas Paper No. 3670. Douglas Aircraft Co. Inc., Santa Monica, CA. (Available from National Technical Information Service, Springfield, VA.)nGreszczuk, L. B. 1969. Shear-modulus determination of isotropic and composite materials. In Composite materials: Testing and design. ASTM STP460.nNorris, C. B. 1955. Strength of orthotropic materials subject to combined stresses. U.S. For. Prod. Lab. Report 1816.nPerry, C. C., and H. R. Lissner. 1962. The strain gage primer. McGraw-Hill, New York.nRadcliffe, B. M. 1955. Determining elastic constants of wood by electric resistance strain gages. Forest Prod. J. 5(1):77-80.nSchuldt, J. P. 1972. Unified testing procedure for determining the elastic parameters of wood. Ph.D. thesis, Colorado State University, Fort Collins, CO.nSliker, A. 1967. Making bonded wire electrical resistance strain gages for use on wood. Forest Prod. J. 17(4):53-55.nSliker, A. 1989. Measurement of the smaller Poisson's ratios and related compliances for wood. Wood Fiber Sci. 21(3):252-262.nU.S. Forest Products Laboratory. 1987. Wood handbook: Wood as an engineering material. (USDA Agri. Handb. 72 rev.) U.S. Gov. Print. Off., Washington, DC.n






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