Yield and ultrasonic modulus of elasticity of red maple veneer.

摘要

The purpose of the study was to assess the potential for using red maple sawlogs to manufacture laminated veneer lumber (LVL). The primary objective was to determine the yield of ultrasonically graded veneer from red maple logs. A sample of 48 logs was obtained from six Eastern and Lake States in the United States. The logs were visually graded and shipped to a plywood manufacturing facility in northern Michigan where they were debarked, steamed for 72 hours, and then rotary peeled into nominal 1/8-inch-(standard 3-mm-) thick veneer. Special care was taken to ensure that each veneer sheet could be traced back to the log from which it came. The veneer sheets were dried to approximately 12 percent moisture content at the plywood mill, shipped to the USDA Forest Service, Forest Products Laboratory in Madison, Wisconsin, and nondestructively tested using a commercially available ultrasonic veneer grader. The average stress wave speed, obtained from the veneer grader, and the density of each sheet was used to compute its modulus of elasticity (MOE). Veneer yield and MOE were compared on the basis of geographical region of log origin: Lake States (Michigan and Wisconsin) and Eastern States (New York, Pennsylvania, Vermont, and West Virginia). Veneer yield was tabulated based on four categories: 54-inch-(137-cm-) wide sheets, 36-inch-(91-cm-) wide sheets, strips, and fishtails. The only major difference in yield between the two regions was observed in the No. 2 logs. The Eastern States' No. 2 logs yielded approximately 13 percent more of the original log volume as 54-inch (137-cm) sheets. The MOE comparisons were based on results from the 54-inch (137-cm) sheets because the yield of 36-inch (91-cm) sheets was low. When grouped, the yield of 54-inch (137-cm) veneer sheets was similar for the No. 1 and No. 2 logs, but lower from the No. 3 logs. Decreases in the total veneer yield corresponded with decreases in log quality. The MOE values of veneer from all logs had a mean value of 1.80x106 lb./in.2 (12.4 GPa) and a standard deviation of 0.33x106 lb./in.2 (2.3 GPa).