Determination of cohesive laws in wood bonded joints under mode II loading using the ENF test

Cohesive laws of wood bonded joints under mode II loading were determined using two different methods. The direct method requires the establishment of the relation between the strain energy release rate under mode II loading (GII) and the corresponding crack tip shear displacement (CTSDII). An equivalent crack length procedure was used to assess the evolution of GII, with remarkable advantages relatively to classical data reduction schemes. The CTSDII was determined from displacements measured by digital image correlation. The cohesive laws were obtained by differentiation of a logistic function fitted to the GII=f(CTSDII) relation. The inverse method is based on an optimization procedure using a genetic algorithm with the objective to determine the cohesive law providing the best agreement between numerical and experimental load–displacement curves. Four parameters of the adjusted trapezoidal law were obtained in this optimization procedure. Both direct and inverse methods propitiated excellent agreement between numerical and experimental load–displacement curves, thus revealing their adequacy to determine cohesive laws of wood bonded joints under mode II loading.