Mechanical Properties of Small Clear Specimens and Visually Graded Lumber from Living and Spruce Budworm-Killed Balsam Fir

Small clear specimens from living balsam fir and from spruce budworm-killed balsam fir dead 3 months, 12 months, and 22 months were tested in bending and compression perpendicular to the grain. Results indicated that modulus of rupture (MOR) of specimens from budworm-killed trees dead 3 months or more was significantly lower than MOR of specimens from living trees. Modulus of elasticity (MOE) appeared to be less sensitive to changes in budworm-killed material than MOR. Stress at the proportional limit for compression perpendicular to the grain was significantly lower for specimens from trees dead 22 months than for specimens from living trees. Both MOE and MOR in bending were determined for visually graded nominal 2- by 4-inch lumber from living and spruce budworm-killed balsam fir dead 12 months and 22 months. Average MOE values for living balsam fir were 1.274 x 106 psi, 1.217 x 106 psi, and 1.175 x 106 psi for Construction, Standard and Utility grades, respectively. Average MOR values for the same grades of living material were 4,699 psi, 4,684 psi, and 4,352 psi, respectively. Average MOE and MOR for Utility grade lumber from both spruce budworm-killed categories were not significantly different from the average MOE and MOR for living balsam fir. Statistical analyses of the MOE and MOR data for Construction and Standard grades of budworm-killed lumber were not performed due to the small sample sizes