EVALUATION OF FAILURE CRITERIA FOR SHEAR STRENGTH IN WOOD ADHESIVE JOINTS WITH INCLINED GRAINS UNDER TENSION AND COMPRESSION LOADS

Abstract

This study applied six failure criteria to estimate the shear strength of wood adhesive joints subjected to tension and compression loads as a function of fiber inclination. Shear stresses in the adhesive line were determined through experimental tests using specimens obtained from 12 Eucalyptus saligna beams. These specimens were prepared with variable fiber inclinations (0º, 15º, 30º, 45º, 60º, 75º, and 90º) relative to the load application, following the NBR 7190 standard. The experimental results were statistically analyzed in conjunction with the six failure criteria (Hankinson, DIN 1052, Tsai-Hill, Hyperbolic, Keylwerth, and Karlsen), allowing for the adaptation of the models to determine the shear strength of the adhesive line as a function of fiber inclination. In their original form, the Hankinson, DIN 1052, Tsai-Hill, and Hyperbolic models did not show statistical significance (p < 0.05). However, after modifications, all models demonstrated statistical significance, with the best fits being provided by the DIN 1052, Keylwerth, Hankinson, Karlsen, Hyperbolic, and Tsai-Hill models, in order of significance. Due to ease of application, the most recommended models for predicting the shear strength values of the adhesive line under compression and tension, as a function of fiber inclination, are the DIN 1052 and Hankinson formulas.