Experimental and numerical evaluation of the structural performance of Uruguayan Eucalyptus grandis finger-joint

The aim of this study was to evaluate the structural performance of finger-joints made of Uruguayan Eucalyptus grandis and two types of adhesives. A numerical model for bending strength and stiffness prediction was developed. Model inputs were experimentally determined from tests on wooden specimens and from the literature. Finger-joints glued with two types of adhesives (one-component polyurethane -PUR- and emulsion polymer isocyanate-EPI-) were tested in bending and the failure modes were evaluated. Results show that adhesive type did not influence the stiffness of the finger-joint, but the bending strength. Specimens glued with PUR showed higher strength than those glued with EPI. A 3D model, using Comsol Multiphisic software, was developed to simulate the finger-joint behavior. Adhesive-wood interaction in the finger-joints was modelled using the Comsol Thin Elastic Layer module, defined by the elastic properties of the adhesives. The numerical results showed no differences on the stiffness of the joints regardless of adhesive type. Results agreed with those obtained from experimental tests, with a maximum error of 7%. Models predicted the bending strength with an error of 6% with respect to the experimental values. Different finger configurations were analysed, and the optimal geometry (20 mm-length, 6.2 mm-pitch and 1.0 mm-tip-thick) to attain the maximum strength for Uruguayan Eucalyptus was found.