A fatigue life prediction method of adhesively bonded joints based on visco-elastic and visco-plastic behavior: application under cyclic shear loading

Abstract

International audienceTo perform an evaluation of the abilities of a bonded structure to endure repetitive loadings, characterizations of structural adhesive joints mechanical behavior are key objectives. The aim of this study is to describe the phenomena occurring in the bonded joint until the appearance of a macroscopic crack. Using lap-shear type specimens, associated with stress concentrations, crack initiation generally appears early at the edge of the adhesive joint, which makes it difficult to identify the crack initiation phase. To characterize more properly the crack initiation phase, bonded joints designed to limit stress concentrations allowed the accurate characterization of the mechanical phenomena occurring in a polyurethane structural ductile adhesive. Then, based on the experimental response of the bonded assembly to creep recovery tests, a visco-elastic visco-plastic behavior law is defined for the adhesive joint mechanical behavior. In the following, details of such a model able to take into account the hydrostatic sensitivity with a non-associated formalism are given. The numerical work performed here relies on the identification of the material parameters of the behavior law using creep-recovery tests to model the cyclic behavior of bonded structures. Then, experimental results under fatigue loading are presented and compared to numerical simulations. Finally, using a strain-based criterion for the definition of crack initiations, predictions of fatigue lifetime are performed for specimens under shear loadings. The quality of the results obtained underlines that an accurate description of viscous mechanisms in the adhesive layer allows describing efficiently the mechanical behavior of bonded joints under cyclic loading

A viscoelastic–viscoplastic model for adhesives subjected to reversed cyclic load

“…Some adhesives behave differently in tension and compression because of the influence of hydrostatic stress on the nonlinear behaviors. Several experimental investigations involving multiaxial stress states, such as Arcan joints (Bidaud et al 2016;Suwanpakpraek et al 2020), lap shear joints (Srinivasan, Ravichandran, and Idapalapati 2020;Zgoul and Crocombe 2004), scarf joints (Afendi, Teramoto, and Bakri 2011;Carrere et al 2015), and tubular butt joints (Arnaud, Créac'Hcadec, and Cognard 2014;Cognard et al 2012), have shown that the yield and failure of adhesives were influenced by hydrostatic stress.…”