Digital image correlation (DIC) application to evaluate bending performance of timber beams strengthened with NSM-CFRP plate

Abstract

This study presents the use of open-source digital image correlation (DIC), an advanced non-contact optical technique for measuring strain and deformation, to evaluate the bending performance of strengthened laminated veneer lumber (LVL) timber beams under a four-point bending test. The beams were strengthened with a carbon fibre-reinforced polymer (CFRP) plate mounted near the compression side, known as near-surface mounted (NSM). The effect of the reinforcement ratio on the compression zone was experimentally investigated for the strengthened beams. Open-source Ncorr software was employed to track surface patterns and measure full-field displacement and strain. This study demonstrated that DIC techniques provided accurate strain measurements and displacement analysis that closely matched experimental values, confirming the reliability of this open-source DIC system. DIC also revealed strain fields developing before and after the onset of cracking, providing insight into the contour failure of the timber beam. The strain fields obtained from DIC were found to be in excellent agreement with the crack pattern from the experimental results. Additionally, DIC results for displacement analysis and elastic stiffness were in good accord with experimental observations and beam theory for displacement calculation, further confirming the reliability and effectiveness of DIC as an analytical technique. The results of this study also have practical implications by highlighting the potential of open-source DIC techniques in the same way as commercial DIC software for ensuring accuracy and efficiency in materials testing and analysis for structural applications, particularly in timber composite materials.