MANUFACTURE OF CYLINDRICAL LVL BY SPIRAL- WINDING METHOD .1. EFFECT OF INTERLOCKED-PLIES ON THE TENSILE YOUNGS MODULUS

The fundamental characteristics of manufacturing cylindrical laminated veneer lumber (LVL) by a spiral winding method were studied. The mate rial made by this method has a grain sloped to the longitudinal axis o f the cylinder. To minimize the reduction of Young's modulus due to th e sloped grain and to reinforce the weakness of the splitting strength along the grain, the veneer tapes are wound in the clock-wise and cou nter clock-wise directions alternately resulting in an interlocked gra in of the cylinder wall. In the present paper, the effect of the inter locked grain structure of the LVL on Young's modulus was calculated th eoretically and was verified by experiments. In order to verify the re sults of calculations, the tensile Young's moduli of the veneer specim ens from spruce (Picea spp.), then those of the laminates with interlo cked grains made from the same specimens were measured. The tensile Yo ung's moduli of specimens with interlocked grain were greater than tho se of specimens without interlocked grain. When the angles between the interlocked grains were small, especially less than 10 degrees, the Y oung's moduli only decreased a little compared to 0 degrees. Because t he theoretical curves match the experimental values, the effect of the interlocked grain structure can be predicted from this theoretical cu rve.