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

Abstract

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.

Experimental deformation analysis of an adhesively bonded multi‐material joint for marine applications

“…Fs-2 and FsC-2) are subjected to stepwise loading/unloading tensile tests with a load increase of T A B L E 1 Mechanical properties. [37,43] Steel AH- The cracked specimen tested in stepwise loading mode (FsC-2) failed at a higher force, that is, 89.6 kN.…”

“…Likewise, Thäsler et al [ 36 ] suggested a method to monitor and trace the crack in dynamically loaded single‐lap shear, double‐lap shear and crack lap shear specimens using 2D DIC. Jaiswal et al [ 37 ] applied DIC to evaluate the deformation of single‐ and double‐lap specimens with thick layers of MMA subjected to fatigue loading.…”

Durability of an adhesively bonded joint between steel ship hull and sandwich superstructure pre-exposed to saline environment

“…All tests were performed at room temperature. The test rig records load versus cross-head displacement data as per the test methodology described in (30). The local deformations and strains in the adhesive bondlines at the side surface of the joint are obtained by post-processing images captured by DIC during testing.…”

“…The joint geometry had been designed for marine applications and test specimens having the real dimensions were manufactured. This work is part of the Interreg project Qualify in which first some series of small-scale and coupon tests have been performed to quantitatively evaluate the mechanical performance of adhesively bonded joints (22,24,34,(26)(27)(28)(29)(30)(31)(32)(33). Qualify established a clear relation between stiffness degradation and increase in hysteresis losses on the one hand, and increasing number of fatigue cycles on the other hand, for double lap joints with thick MMA adhesive layer (30).…”

DIC Based Strain and Damage Analysis of Large Scale Steel to Composite Adhesive Joints Subjected to Tension and Compression Loading

“…The project's main goal is to provide qualification guidelines for real scale adhesive joints for lightweight and safe maritime transport. In this project, different types of small and large-scale (bi-material) joints bonded with a thick layer of methyl methacrylate adhesive have been subjected to various mechanical and environmental loads to quantitatively evaluate their mechanical performance (Saeedifar et al, 2019;Jaiswal et al, 2020;Jaiswal, Kumar and De Waele, 2020;Saleh et al, 2020;Askarinejad et al, 2021;Iyer Kumar, Jaiswal and De Waele, 2022;Jaiswal, Iyer Kumar, et al, 2023;.…”