Effect of Various Proportions of Juvenile Wood on Laminated Veneer Lumber

摘要

To satisfy the increased demand for forest products while addressing environmental concerns, much of the future timber supply will be from managed plantations of rapidly grown trees. These trees will be harvested in short-rotation cycles and will contain large quantities of juvenile wood. The report discusses the influence that Douglas-fir and Southern Pine juvenile wood has on veneer grading and its implications on structural performance of laminated veneer lumber (LVL). Veneer blocks cut from fast-grown Douglas-fir and Southern Pine lumber were examined and divided into three zones based on age: mature, transition, and juvenile. Veneer peeled from these zones was tracked through the peeling, drying, and grading process. The LVL made ov various proportions of juvenile and mature veneer was tested in flatwise bending, edgewise bending, and tension. Results of the study suggest that two forms of nondestructive grading techniques are capable of placing juvenile material in a low-grade classification. Also, during veneer preparation, the low strength of juvenile wood veneer in both species led to a significant increase in breakage during handling when compared to normal veneer losses.