Analysis of poplar timber finger joints by means of Digital Image Correlation (DIC) and finite element simulation subjected to tension loading

Due to the strong demand for wood, and the need to reduce the carbon footprint in construction, fast-growing low-graded planted species like poplar are promising wood for the supply chain in the context of engineered wood products, EWPs. Finger joints constitute a key technology for the manufacture of long structural elements of EWPs. Thus, evaluation of the mechanical properties of finger joints is important when designing these structural members. This paper shows the results of mechanical behaviour in tension of poplar timber of the I-214 cultivar, for specimens with and without finger joints, using experiments monitored by DIC (Digital Image Correlation) and simulated by the Finite Element Method. For moderate and intermediate loads, the samples with finger joints showed behaviour similar to those without joints. However, the presence of the fingers decreased the mechanical properties of the modulus of elasticity in the longitudinal direction anywhere from 7.7 to 23.7%; and there was a decrease of around 27.5% in tensile strength. An agreeable correlation between the DIC results and FEM simulations is obtained for the longitudinal, transversal, and shear strain fields, thus demonstrating the high potential of both methodologies.