Influence of face grain angle, size, and moisture content on the edgewise bending strength and stiffness of birch plywood

Abstract

Birch plywood exhibits outstanding mechanical properties with regards to tensile, compressive, and shear behaviors, making this engineered wood product promising in timber connection applications. However, the edgewise bending strength and stiffness, which are often critical for the design of gusset plates, have not been investigated thoroughly. Moreover, in engineering applications, the size and moisture content of the plywood plate are in general very different from those adopted in laboratory testing according to current standards. This paper aims to investigate the influence of face grain angle, size, and moisture content on the edgewise bending strength and stiffness of birch plywood. In total, 288 birch plywood specimens were tested in three-point bending at five different face grain angles to the beam longitudinal axis (from 0° (parallel) to 90° (perpendicular), with an angle step of 22.5°), with four different sizes (with the nominal depth of 20 mm, 30 mm, 40 mm, and 50 mm) and three different moisture contents (7.2 %, 11.9 %, and 21.8 %). Analytical and numerical models, both taking non-linear elasto-plastic compressive behaviors into account, were developed for the prediction of the ultimate moment capacity based on different failure definitions. Lastly, the relationships between the bending strength and elastic modulus were analyzed.

Keywords

• Birch plywood
• Edgewise bending
• Face grain angle
• Size effect
• Property-moisture relationships