A model of the effect of strand angle and grain angle on the strength properties of oriented veneer and strand wood composites

摘要

A model has been developed of the effect of grain and strand angles, parallel and cross oriented veneer and strand layers, and veneer and strand thickness, on the strength properties of oriented veneer and strand products such as laminated veneer lumber, oriented strandboard, and oriented strand lumber. Cross oriented strands and veneers in oriented strand and veneer products reduce the rate at which strength is reduced with increasing strand and grain angle over the range 0 to 30 degrees. This reduction, in rate of decrease, is directly related to the proportion of cross oriented layers and inversely related to the strand thickness. The failure mode between cross oriented strands and veneers is primarily interlaminar shear and it is postulated that the net perpendicular strength per unit thickness is a function of the proportions of contiguous layers in opposing angular quadrants and contiguous layers in the same angular quadrant. Use of the net perpendicular strength per unit thickness in the Hankinson equation predicts that decreasing the thickness of cross oriented strands will decrease the rate of strength reduction with increasing strand angle and will increase the strength properties attained for any mean strand angle.