Influence of adhesive thickness on the behaviour of bonded assemblies under shear loadings using a modified TAST fixture

This paper presents contributions of numerical modelling for the analysis of adhesively bonded assemblies for marine applications. Such applications are often characterised by relatively thick, 0.5 mm or more, adhesive joints and by a possible variability of the bond line thickness associated with large-scale structures manufactured in boatyard environment. Experimental and numerical analysis in the case of shear tests are proposed to study the influence of bond line thickness on the mechanical behaviour of the adhesive. In order to accurately analyse the complete non-linear behaviour of an adhesive in an assembly, specimens with low edge effects have to be used. An increase in the thickness of the bond line leads to an increase in the influence of the edge effects, computed under elastic assumption. As those numerical results are not able to completely analyse all the experimental observations, various 2D simulations, with refined meshes, taking into account the non-linear behaviour of the adhesive are proposed to complete the analysis. Even for bonded assemblies with low edge effects, computed under elastic assumptions, the analysis of the stress distribution throughout the thickness of the joint, taking into account the non-linear behaviour of the adhesive underlines that an increase in the bond line thickness leads to an increase in equivalent plastic deformation close to the free edges. This property can explain that an increase in the bond line thickness can lead to a reduction in the transmitted load associated to crack initiation.