Finite element analysis of flexural strengthening of timber beams with Carbon Fibre-Reinforced Polymers

Abstract

This study focuses on the flexural behaviour of timber beams externally reinforced using Carbon Fibre-Reinforced Plastics (CFRP). A non-linear finite element analysis was proposed, and was validated with respect to experimental tests carried out on seven beams. All the beams had the same square cross-section geometry and were loaded under four-point bending, but had different numbers of CFRP layers. The Abaqus software was used, and different material models were evaluated with respect to their ability to describe the behaviour of the solid timber beams. Elasto-plastic behaviour with damage effect was assumed for the timber material, linear elastic isotropic model was used for the CFRP, and a cohesive model was used to represent the interaction between two adherent surfaces (CFRP and timber). These two surfaces were paired and, taking into account the presence of an adhesive layer, one of them was defined as the master surface whilst the other was the slave surface. Predicted and measured load–mid-span deflection responses and failure modes were compared. The increases of flexural strength for the two different reinforcement schemes with 2 and 3 layers of CFRP composite sheets were 41.82% and 60.24%, respectively, with respect to the unreinforced timber beams. The maximal difference between calculated and experimental ultimate load-bearing capacity for reinforced solid timber beams with 2-layers of CFRP was around 1.2%.