Physical and bending properties of beech laminated veneer lumber reinforced with carbon fiber fabric

Nine-layer laminated veneer lumber (LVL) 1300 by 850 mm, in nominal thickness of 20 mm, was produced using beech veneer and reinforced LVL (RLVL), by inserting carbon fiber fabric between the veneer sheets. The research aimed to assess the enhancement of flexural properties, both in edgewise and flatwise bending, of beech LVL reinforced with carbon fiber fabric. Two types of reinforcements were made, using two types of adhesives: phenol-formaldehyde (PF) and polyurethane (PUR), in the industrial conditions. In the first group of samples (K1), the reinforcements were placed further from the neutral axis, and in the second group (K2) closer to the neutral axis. These groups were compared to the unreinforced control sample (K). Some physical properties, bending behavior parallel to the grain, and failure mode were determined and analyzed. Edgewise bending strength of the RLVL was about 11% higher than the control in the case of PF adhesive, while flatwise bending strength was about 40% lower than the control in the case of PUR adhesive. The experimental data were verified using the ANOVA model. The most important results of the study define different behavior and fracture mechanisms for each reinforcement and adhesive, highlighting the potential of RLVL for structural applications.