Bending Strength of Douglas-Fir Veneer

Four factors which might permanently affect the bending strength of Douglas-fir veneers were investigated. These were: a) Four drying temperatures from 225? to 450? F, b) four drying times in dryer from just ovendry to O.D. plus 60 minutes, c) four veneer thicknesses from 0.025 to 0.140 inch, and d) seven trees. Veneers were re-humidified in an atmosphere of 70?F and 32 percent RH before testing. Specimens were tested in static bending. As measured by the modulus of rupture, strength loss at 375?F is negligible but can be serious at 450?F. Strength is also seriously reduced by oven-drying veneers at 450?F. Cells on the surface of the veneers are degraded up to 35 percent more than those in the center. Various graphs show the interaction of the test variables. It was noted that the data can be confounded by the variability of lathe checks from veneer to veneer. Specimens with abnormal checks should be eliminated from any analysis.

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