Effect of double-density incising on bending strength of lumber

An experimental study has been conducted to evaluate the effect of a double-density incising method and chromated copper arsenate (CCA) pressure treatment on the bending strength and modulus of elasticity (MOE) of No. 2 and better nominal 2- by 4-inch (38- by 89-mm) Spruce-Pine-Fir lumber. The double-density incising method, developed by Forintek Canada Corp., involved using a system of synchronized pairs of incising rollers with thin sharp teeth to lay down two superimposed patterns of incisions on lumber in the green condition. An incision density of 1,090/square ft. (11,720/m2) was achieved, which allowed white spruce, lodgepole pine, and alpine fir to achieve equivalent penetration with CCA by pressure treatment. Approximately 2,000 specimens were sorted into 8 matched groups according to their average flatwise MOE values and were tested in third-point bending. The eight groups were then given various combinations of incising patterns and pressure treatment level. The results indicate that the fifth percentile bending strength was reduced by 25 percent and the mean MOE was reduced by 6 percent in double-density incised and pressure-treated lumber compared to unincised and untreated lumber.

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