Mechanical Properties Of Individual Southern Pine Fibers. Part II. Comparison Of Earlywood And Latewood Fibers With Respect To Tree Height And Juvenility
Keywords:Loblolly pine, stiffness, strength, microfibril angle, modulus of elasticity, ultimate tensile stress, whole tree variation, juvenile wood
AbstractThis paper reports variations in mechanical properties of individual southern pine fibers and compares engineering properties of earlywood and latewood tracheids with respect to tree height and juvenility. Results indicate that latewood fibers exhibit greater strength and stiffness than earlywood fibers irrespective of tree height or juvenility. Average earlywood loblolly pine fibers had modulus of elasticity and ultimate tensile stress values of 14.8 GPa and 604 MPa, respectively. Corresponding latewood fibers had modulus of elasticity and ultimate tensile stress values that were, respectively, 33 and 73% higher. These differences are attributable to microfibril angles and pitting. Juvenility as defined by the mechanical properties of individual wood fibers is not a cylindrical cone surrounding the pith but appears to be biconical, tapering from the base to below the live crown and then again from the live crown to the apex.
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