Adhesive bond characterization under mixed-mode I + II loading using the mmb test

Abstract

This study presents an experimental method to determine mixed mode cohesive law of adhesive joints in mixed mode.

In the proposed method, based on the Mixed Mode Bending test, the J-integral and crack tip relative displacements are determined based on an equivalent crack length method by processing the global load–displacement curve, without monitoring the crack length, the bending rotations at the loading points and the crack tip relative displacement during the test.

The precision of the method is validated experimentally comparing the results obtained by the proposed methods with those obtained by the Direct Method, where the fracture toughness is determined based on the rotations of the load introduction points and the crack tip displacement is directly measured.

Results reveal that the proposed data reduction scheme is suitable to obtain the mixed mode characterization of an adhesive joint monitoring only the load–displacement curve, without any external displacement measurement technique and without any assumption of the form of the cohesive law.