Screw withdrawal strength of heat-treated and laminated veneer lumber reinforced with carbon and glass fibers

Abstract

The strength of a structural system often depends on the interconnections between the components of the structure. Screws are one of the most widely used fasteners in construction. In this study, the screw withdrawal strength of heat-treated scotch pine (Pinus sylvestris L.) samples reinforced with glass and carbon fibers via Desmodur-vinyl trie ketonol acetate adhesive was investigated. Before manufacturing the laminated veneer lumber, the wood samples were subjected to heat treatment at a temperature of 150 °C, 170 °C, 190 °C, and 210 °C for 2 h. Test results showed that the reinforcement fiber type and heat treatment temperatures had a considerable effect on the screw withdrawal strength. Heat treatment reduced the screw withdrawal strength, while the samples reinforced with both fibers had higher screw withdrawal strengths than those without reinforcement. Reinforcement with glass and carbon fibers increased the screw withdrawal strength up to 38% and 49% in the tangential, 13% and 20% in the radial, and 17% and 25% in the axial direction, respectively, compared to solid wood. In addition, the laminated veneer lumber samples reinforced with carbon fiber had a considerable increase in the screw withdrawal strength compared with the solid wood and glass fiber reinforced samples.