Tension-Perpendicular-to-Glueline Strength of Douglas-Fir Lumber Laminated at High Temperatures

J. C. Bohlen


Preheated Douglas-fir was laminated with high-temperature phenol-resorcinol and ureamelamine adhesives employing the residual heat in the wood to accelerate the cure. Tension specimens were prepared from these laminations, as well as from conventionally glued-laminated wood and wood that was not glued. Prior to testing, one-half of the specimens were conditioned at room temperature and the other half received a 24-hr cold water soak. All glued specimens were weaker than the solid-wood specimens. In the dry condition, the heat-treated material was comparable in strength to conventionally glued specimens. When tested wet (an estimate of durability), the strength reduction of the heat-treated wood glued with phenol-resorcinol ranged from 42% for treatments at 380 F (193 C) to 56% for treatments at 500 F (260 C). In contrast, the conventionally glued material was reduced in strength by only 8%, which compares with published values for solid wood. Thus, the heat-treated wood formed gluelines that are presumably less durable in tension than the conventionally glued-laminated wood.


<i>Pseudotsuga menziesii</i>;glued-laminated beams;tensile strength;glue-line durability;phenol resorcinol

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