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Title: Influence of juvenile wood content on shear parallel, compression, and tension transverse to grain strength and mode I fracture toughness for loblolly pine

Source: Research Paper FPL-RP-647. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 25 pages.

Author(s)Kretschmann, David E.

Publication Year: 2008  View PDF »

Category: Research Papers
Associated Research Project(s):   FPL-4714-1A

Abstract: To satisfy the increased demand for forest products, much of future timber supply is expected to be from improved trees grown on managed plantations. This fast growth resource will tend to be harvested in short-age rotations and will contain higher proportions of juvenile wood than those of current harvests. In anticipation of this resource, definitive information is needed about the influence of juvenile wood on lumber properties so that grading rules or the associated allowable design stresses can be modified as needed. Most information developed to date has concentrated on ultimate tensile stress, modulus of rupture, and modulus of elasticity. This paper reports test results for shear stress parallel-to-grain, compression and tension-stress perpendicular-to- grain, and mode I fracture toughness for various percentages of juvenile wood content and ring orientations. The clear wood properties were measured on over 340 specimens from a 28-year-old fast-grown plantation of loblolly pine (Pinus taeda L.) in North Carolina. The average value of all properties decreased with increasing amounts of juvenile wood in the cross section by as much as 30%. Shear strength was insensitive to annual ring orientation and seemed to be strongly dependent on just the reductions in density. Compression and tension perpendicular-to-grain strength and mode I fracture toughness were very sensitive to annual ring orientation. The results are of significance to all producers of the plantation-grown product because of the concern that fast-grown lumber from plantations may have lower allowable design stresses than those currently published for visually graded lumber.

Keywords: juvenile wood, ring orientation, tension perpendicular-to-grain, compression perpendicular-to-grain, modulus of elasticity, loblolly pine, Southern Pine.

File size: 3 kb(s)

This publication is also viewable on Treesearch:  view
RITS Product ID: 26122
Current FPL Scientist associated with this product
Kretschmann, David E.
Research General Engineer
  

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