Mechanical properties of lodgepole pine containing beetle-transmitted blue stain

A study was conducted to compare the toughness, bending modulus of rupture (MOR), bending modulus of elasticity (MOE), and truss plate connector grip capacity in tension, between wood infected with blue stain transmitted by the mountain pine beetle and non-stained wood. The blue-stained and non-stained lumber samples used in the study were nominal 2- by 4-inch kiln-dried lodgepole pine obtained from 14 sawmills in British Columbia, Canada. Small, clear specimens were prepared from the lumber samples for testing. The data obtained were analyzed by the Student?s t-test and Mann-Whitney U-test to assess whether any significant differences in the above properties exist between the blue-stained and non-stained wood. Blue-stained and nonstained wood had comparable bending MOR, but the former had marginally greater mean bending MOE than the latter. Similarly, the blue-stained wood showed greater mean connector grip capacity compared to non-stained wood. Blue-stained wood showed marginally lower mean toughness compared to non-stained wood, but both had comparable toughness below the lowest quartile of the toughness distribution. The small differences observed associated with blue stain, i.e., 5 percent decrease in mean toughness, 1 percent increase in mean MOE, and 6 percent increase in mean connector grip capacity, are likely to be masked by differences in mechanical properties of the heartwood and sapwood, and by the presence of strength-reducing characteristics, such as knots and slope of grain, in full-size lumber. The MOR and MOE obtained in this study were greater than the published values. Overall, the blue stain did not have a negative effect on the mechanical properties of the wood.

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