Orthotropic Strength and Elasticity of Hardwoods in Relation to Composite Manufacture Part III: Orthotropic Elasticity of Structural Veneers
Keywords:
Orthotropy, hardwood, tensile MOEAbstract
Structural veneers approximately 3.2 mm (1/8 in.) in thickness are widely used as basic constituents in structural composites such as plywood, laminated veneer lumber (LVL), and parallel strand lumber (PSL). The veneer processing operation (peeling) may adversely alter the mechanical properties of the wood substance by introducing compression-set, cracks, and splits, etc. The modulus of elasticity (MOE) in tension of five hardwood species, which are potential raw materials for composite manufacture, was investigated in veneer form. The experimental work included dynamic MOE determination using ultrasound stress wave timing and static MOE measurements for comparison purposes. The orthotropy of MOE in the longitudinal-tangential (LT) plane was also a target of the investigation. Theoretical models were fitted to experimental data that may predict the MOE of the constituents according to their position within the consolidated composites. Experimental and analytical results indicated that a combined model including the Hankinson's formula and an orthotropic tensorial approach is the best estimator for MOE of veneers having inclined grain orientation. Furthermore, the relationship between static and dynamic MOE values may be obtained by second-order polynomial models.References
American Society for Testing and Materials (ASTM). 1996a. Standard Methods of Testing Small Clear Specimens of Timber ASTM D 143-94. ASTM, West Conshohocken, PA.nAmerican Society for Testing and Materials (ASTM). 1996b. Standard Test Methods for Specific Gravity of Wood and Wood-base Materials ASTM D 2395-93. ASTM, West Conshohocken, PA.nAmerican Society for Testing and Materials (ASTM). 1996c. Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-base Materials ASTM D 4442-92. ASTM, West Conshohocken, PA.nDivos, F., and T. Tanaka. 2000. Effect of creep on modulus of elasticity determination of wood. ASME J. Vibration Acoust.122(1):90-92.nDivos, F., I. Daniel, and L. Bejo. 2000. Defect detection in timber by stress wave technique. In Proc. Int. Conf. on Wood and Wood Fiber Composites, 13-15 April, 2000, Stuttgart, Germany.nGerhards, G. C. 1988. Effect of slope of grain on tensile strength. Forest Prod. J.38(7/8):39-40.nHankinson, R. L. 1921. Investigation of crushing strength of spruce at varying angles of grain. Air Service Information Circular No. 259, U.S. Air Service, 1921.nHunt, M. O., M. H. Triche, G. P. McCabe, and W. L. Hoover. 1989. Tensile properties of yellow-poplar veneer strands. Forest Prod. J.39(9):31-33.nJung, J. 1979. Stress-wave grading techniques on veneer sheets. Gen. Tech. Rep. FPL-GTR-22. USDA Forest Serv., Forest Prod. Lab., Madison, WI.nJung, J. 1982. Properties of parallel-laminated veneer lumber from stress-wave-tested veneers. Forest Prod. J.32(7):30-35.nKaiserlik, J. H., and R. F. Pellerin. 1977. Stress-wave attenuation as an indicator of lumber strength. Forest Prod. J.27(6):39-43.nKimmell, J. D., and J. J. Janiowak. 1995. Red maple and yellow-poplar LVL from ultrasonically rated veneer. Forest Prod. J.45(7/8):54-58.nKoch, P., and G. E. Woodson. 1968. Laminating butt-jointed, log-run southern pine veneers into long beams of uniform high strength. Forest Prod. J.18(10):45-51.nKollman, F. P. P., and W. A. Côté, Jr. 1968. Principles of wood science and technology, I. Springer-Verlag, New York, NY.nLang, E. M., L. Bejo, J. Szalai, and Z. Kovacs. 2001. Orthotropic strength and elasticity of hardwoods in relation to composite manufacture. Part I. Orthotropy of shear strength. Wood Fiber Sci.32(4):502-519.nLang, E. M., L. Bejo, J. Szalai, and Z. Kovacs., and R. B. Anderson. 2002. Orthotropic strength and elasticity of hardwoods in relation to composite manufacture. Part II. Orthotropy of compression strength and elasticity. Wood Fiber Sci.34(2):350-365.nPellerin, R. F. 1965. Vibrational approach to nondestructive testing of structural lumber. Forest Prod. J.15(3): 93-101.nPu, J., and R. C. Tang. 1997. Nondestructive evaluation of modulus of elasticity of southern pine LVL: Effect of veneer grade and relative humidity. Wood Fiber Sci.29(3):249-263.nPugel, A. D. 1990. Angle-to-grain tensile strength specimen for thin wood samples. Forest Prod. J.40(2):49-51.nRiccati, J. 1747. Verae et Germanae virim elasticarum leges ex phaenumenis demonstratae. De Bononiensi Schientarium Academia Commentarii 1:523. Bogona.nRippy, R. C., F. G. Wagner, T. M. Gorman, H. D. Layton, and T. Bodenheimer. 2000. Stress-wave analysis of Douglas-fir logs for veneer properties. Forest Prod. J.50(4):49-52.nRoss, R. J., S. W. Willits, W. von Segen, T. Black, B. K. Brashaw, and R. F. Pellerin. 1999. A stress wave based approach to NDE of logs for assessing potential veneer quality. Part 1. Small diameter ponderosa pine. Forest Prod. J.49(11/12):60-62.nSharp, D. J. 1985. Non-destructive techniques for manufacturing LVL and predicting performance. Pages 100-108 in Proc. Fifth Symp. on Nondestructive Testing of Wood, Washington State Univ., Pullman, WA.nShuppe, T. F., C. Y. Hse, L. H. Groom, and E. T. Choong. 1997. Effect of silvicultural practice and veneer grade layup on some mechanical properties of loblolly pine LVL. Forest Prod. J.47(9):63-69.nSzalai, J. 1994. Anisotropic strength and elasticity of wood and wood based composites. Private ed. Sopron, Hungary. (in Hungarian.)nWang, J., J. M. Biernacki, and F. Lam. 2001. Nonde-structive evaluation of veneer quality using acoustic wave measurements. Wood Sci. Technol.34(2001):505-516.nWoodward, C. B., and J. Minor. 1988. Failure theories for Douglas-fir in tension. J. Struct. Eng.114(12):2808-2813.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.
