Orthotropic properties of loblolly pine (Pinus taeda) strands

Orthotropic properties of loblolly pine strands were measured from growth ring numbers 1-10 and 11-20 using digital image correlation (DIC). Eight elastic properties (E (L) , E (R) , E (T) , G (LR) , G (LT), upsilon(LR), upsilon(LT), and upsilon(RT)) and five strength values (sigma(L), sigma(R), sigma(T), tau(LR), and tau(LT)) of loblolly pine strands were measured. Compliance matrices were derived and used to calculate the maximum normal and shear strains. With the increment of growth ring number, elastic modulus and ultimate tensile strength (UTS) generally increased, whereas shear strength decreased. Statistical comparison showed that elastic moduli, Poisson's ratio, and UTS were highly dependent upon orientation of strands with loading direction. Only elastic modulus and UTS from the longitudinal-radial plane strands were significantly different by the two growth ring positions. More distinctive orthotropic properties of loblolly pine strands from growth ring numbers 11-20 were found associated with more consistent failure modes.