Two tests for adhesive bonding long term characterization: principles and applications

This article describes recent refinement of the traditional wedge test technique used to characterize durability of the adhesive joints. We propose two types of measuring protocols to monitor precisely and continuously the propagation of an "effective" crack during long term mode I fracture mechanic test. First method is directly derived from the traditional wedge test technique and consist in monitoring the surface strain of adherent with resistive gauges. The second method consist in replacing constant applied displacement by constant force loading and monitoring the beam deflection. Applications of these techniques are presented concerning crack propagation and nucleation monitoring leading to better understanding of the phenomena occurring in the joint subjected to an external load.