Issue 53

P. R. Jaiswal et alii, Frattura ed Integrità Strutturale, 53 (2020) 26-37; DOI: 10.3221/IGF-ESIS.53.03

Focussed on the 1st Benelux Network Meeting and Workshop on Damage and Fracture Mechanics

Unified methodology for characterisation of global fatigue damage evolution in adhesively bonded joints

Pankaj R. Jaiswal, Rahul Iyer Kumar, Wim De Waele Soete Laboratory, Department of Electromechanical, Systems and Metal Engineering (EMSME), Ghent University, Belgium.

Pankaj.Jaiswal@Ugent.be, https://orcid.org/0000-0002-9373-4489 Rahul.IyerKumar@Ugent.be, http://orcid.org/0000-0003-1241-2697 Wim.DeWaele@Ugent.be, http://orcid.org/0000-0002-7196-3328

A BSTRACT . This paper reports on the development of a methodology for evaluating the fatigue damage evolution in single and double lap adhesively bonded joints subjected to constant and variable fatigue loading. First, a methodology is developed to monitor the evolution of permanent deformation, stiffness degradation and hysteresis losses of single lap joints subjected to constant amplitude fatigue load. During the test, the global deformation of the adhesive joint is monitored using digital image correlation (DIC). A MATLAB code is developed to analyse and visualize the evolution in stiffness degradation and energy dissipation during the course of a complete fatigue test. Hereto ellipses are fitted to the hysteresis loops in the recorded load-deformation data. The slope of the main axis of the ellipse and its enclosed area are extracted to determine stiffness and dissipated energy, respectively. Next, the methodology is optimized for implementation during fatigue testing of double lap joints with different bond line thicknesses. The results of the experimental study reveal a distinct relation between stiffness degradation and increase in hysteresis losses with increasing number of fatigue cycles or thus increasing fatigue damage. K EYWORDS . Single lap adhesive joint; Double lap adhesive joint; Fatigue test; Hysteresis.

Citation: Jaiswal, P. R., Kumar, R. I., De Waele, W., Unified methodology for characterisation of global fatigue damage evolution in adhesively bonded joints, Frattura ed Integrità Strutturale, 53 (2020) 26-37.

Received: 30.11.2019 Accepted: 28.04.2020 Published: 01.07.2020

Copyright: © 2020 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

I NTRODUCTION

dhesives are widely applied for joining dissimilar materials, and adhesive joints are most noticeable for the development of lightweight structures in aviation, ships or trains as it directly affects fuel economy [1]. In fact, it has been reported that 7% enhancement in fuel efficiency could result from a weight reduction of 10% for a vehicle structure [2]. Whilst in automotive industry spot-welded joints are widely used to reach this purpose [3], the shipbuilding industry has shown a high interest in adhesive bonding. Fiber-reinforced polymers are increasingly being used in the A

26