Abstract

A novel method is presented for the determination of mode II cohesive law for the characterization of delamination in thin adhesive joints The proposed method is based on the three point end notched flexure test. The data reduction method used is the Beam Theory including Bending Rotation effects method (BTBR), which includes the effect of local deformations, shear and bending rotations. By this method, the initial crack length, the apparent crack length during the crack advance, and the mode II resistance curve are determined. The relative shear displacement at the crack tip is determined as a function of the apparent crack advance that occurs when the generation of the fracture zone progresses. In order to determine the shear displacement an analytical analytical model based on the classical theory of beams is used. Finally, the fracture toughness versus the shear relative displacement is represented and the cohesive law is determined by numerical derivation.

Abstract

This work presents an experimental method to determine the cohesive law of thin adhesive joints in mixed mode. The proposed method is based on the MMB (Mixed Mode Bending test). The Energy release Rate and Crack Tip Relative Displacement are determined based on a compliance variation data reduction method by processing the global load displacement curve, without monitoring the crack length and the crack tip relative displacement during the test. Representing the energy release rate versus relative displacement the cohesive law is determined by numerical differentiation. The method is validated numerically by virtual tests including the cohesive zone model. The results reveal that the proposed data reduction scheme is suitable to obtain the mixed mode cohesive law using only the load and displacement data obtained from the testing machine, without any external displacement measurement technique and without any assumption of the form of the cohesive law.