Strength Properties of Tension Wood and Typical Wood in a Leaning Eastern Cottonwood Tree

Shear parallel to the grain and tension perpendicular to the grain of tension wood and typical wood in eastern cotton wood (Populus deltoides Bartr.) were analyzed. The adhesive bonding characteristics of cottonwood tension wood were also investigated. For this, the standard ASTM block-shear specimen and a newer ASTM cross-lap specimen were used to evaluate shear parallel to the grain and tension perpendicular to the grain, respectively. The three room-temperature-setting adhesives used included resorcinol formaldehyde, urea formaldehyde, and polyvinyl resin. A detailed description of the preparation of testing of specimens is presented. Results indicated that in specimens containing tension wood bonded to typical wood, the tension wood appeared to fail more readily than typical wood when stressed in tension perpendicular to the grain. However, typical wood appears to fail more readily than tension wood when tested in shear. Failing strength and wood failures did not differ significantly between tension wood and typical wood for either type of specimen.

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