SHEAR PROPERTIES OF COMPONENTS USED IN STRESSED-SKIN PANELS

In this study, certain mechanical and rheological properties of struct ural lumber subjected to shear stresses and the long-term lateral load -slip behavior of silicone elastomeric and polyvinyl-acetate adhesives (PVA) with an isocyanide hardener were evaluated as part of a larger project designed to predict the long-term behavior of stressed-skin pa nels under load. Sixteen pieces of solid wood and 16 glued joints were evaluated in: several test series in order to determine the desired p roperties. Wood modulus of rigidity was determined from the initial de formation recorded in long-term tests. The relative creep was also det ermined under constant environmental conditions (20 degrees C, 65% RH) . Four combinations of long-term tests on glued joints were conducted on wood-chipboard and wood-steel connections with the two adhesives. A nalyses showed that the creep rate, relative creep, and joint variabil ity were greatest for the silicone adhesive. Two mathematical models ( power functions with and without exponential terms) were evaluated as predictors of the deformation-time relationship for the PVA joints und er constant loading. The power function with the exponential term was found to be the better predictor. However, both underestimated relativ e creep at longer load durations.