Shear Properties of Components Used in Stressed-Skin Panels

Abstract

In this study, certain mechanical and rheological properties of structural 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 panels under load. Sixteen pieces of solid wood and 16 glued joints were evaluated in several test series in order to determine the desired properties. Wood modulus of rigidity was determined from the initial deformation recorded in long-term tests. The relative creep was also determined under constant environmental conditions (20°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. Analyses showed that the creep rate, relative creep, and joint variability 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 under constant loading. The power function with the exponential term was found to be the better predictor. However, both underestimated relative creep at longer load durations.