Strength prediction of adhesive joints after cyclic moisture conditioning using a cohesive zone model

• Published in: Engineering fracture mechanics Vol. 78; no. 16; pp. 2746 - 2760
• Main Authors: Mubashar, A., Ashcroft, I.A., Critchlow, G.W., Crocombe, A.D.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2011; Elsevier
• Subjects: Adhesion; Adhesive joints; Cohesion; Condensed matter: structure, mechanical and thermal properties; Cyclic moisture; Damage; Diffusion in solids; Durability; Exact sciences and technology; Failure; Finite element method; Fracture mechanics; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Mathematical models; Methodology; Moisture; Physics; Solid mechanics; Static elasticity (thermoelasticity...); Strength prediction; Structural and continuum mechanics; Theory of diffusion and ionic conduction in solids; Transport properties of condensed matter (nonelectronic); Finite element method; Durability; Strength prediction; Cyclic moisture; Adhesion; Cohesive end; Epoxy resin; Crack propagation; Adhesive strength; Aluminium alloys; Adhesive joint; Humidity; Water absorption; Modelling; ADiffusion; Damage; Joints; Crack formation; Ruptures; Lap joint; Moisture; Experimental study; Loadbearing capacity; Non linear effect; Memory effect; Structural analysis
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2011.07.010

► Moisture uptake in an adhesive is shown to be dependent on moisture history. ► Cyclic moisture uptake has been predicted incorporating moisture history effects. ► The predicted moisture field has been coupled with a moisture dependent cohesive zone model. ► The methodology has been used to predict failure in moisture conditioned adhesive joints. This paper presents a methodology to predict the strength of adhesive joints under variable moisture conditions. The moisture uptake in adhesive joints was determined using a history dependent moisture prediction methodology where diffusion coefficients were based on experimental cyclic moisture uptake of bulk adhesive samples. The predicted moisture concentrations and moisture diffusion history were used in a structural analysis with a cohesive zone model to predict damage and failure of the joints. A moisture concentration and moisture history dependent bilinear cohesive zone law was used. The methodology was used to determine the damage and failure in aluminium alloy – epoxy adhesive single lap joints, conditioned at 50 °C and good predictions of failure load were observed. The damage in the adhesive joints decreased the load carrying capacity before reaching the failure load and a nonlinear relationship between the load and displacement was observed. Changes in crack initiation and crack propagation were also observed between different types of joints. The presented methodology is generic and may be applied to different types of adhesive joint and adhesive.