Contribution factor of wood properties of three poplar clones to strength of laminated veneer lumber

The term "Contribution Factor" (C-f) was introduced in this paper to indica te the contribution ratio of solid wood properties to laminated veneer lumb er (LVL) strength. Three poplar (Populus sp.) clones were studied, and the results showed that poplar with good solid wood properties has high Contrib ution Factor. The average Contribution Factor of Poplar 69 (Populus deltoid es cv. I-69/55), Poplar 72 (P. euramericana cv. I-72/58), and Poplar 63 (P. deltoides cv.I-63-51) was 76.2%, 68.6%, and 66.1%, respectively. The avera ge Contribution Factor of the three clones for shear strength, modulus of e lasticity (MOE), and impact toughness was approximately 80%, which is highe r than that for modulus of rupture (MOR), compressive strength, and hardnes s. The average Contribution Factor of the six properties tested was highest in Poplar 69 (76.2%) and the lowest in Poplar 63 (66.1%), indicating that the Contribution Factor is positively affected by solid wood properties. De nsification also significantly affects LVL MOE in Poplar 72, as compared to that of Poplar 69. Poplar 63, however, showed highest improvement in MOR s trength from solid wood to LVL and also highest specific LVL MOR, even thou gh it has the lowest solid wood MOR among the three clones.