Numerical approach for the design of adhesively-bonded assemblies

This paper presents contributions of numerical modelling for the optimization of adhesivelybonded assemblies for marine and underwater applications. Difficulty in modelling the failure of even simple joints (lab shear specimens) highlighted the need for more reliable constituent input data [

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;

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]. Therefore, in order to be able to study the behaviour of thin adhesive films up to failure, as a function of the normal stress, a modified Arcan fixture has been developed. Numerical simulations in linear elasticity, for bi-material structures show that the use of special geometry for the substrate (a beak close to the adhesive joint) makes it possible to eliminate the contribution of edge effects [

3

]. Non linear simulations taking into account the fixing system of the substrates on the supporting fixture were used to optimize the design of the complete fixture in order to prevent pre-loading of the adhesive joint. Moreover, in order to have more precise data for design, a study of the evolution of the stresses through the thickness of the adhesive joint under elastic assumption is proposed with respect to the shape of the edge of the adhesive joint. Non-contact extensometry and optimisation techniques have been used to determine the kinematics of the bonded joints deformation. For the epoxy resin Vantico

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Redux 420 the viscoplastic behaviour has been analyse for different radial loadings with the following variables: the applied load and the displacement of both extremities of the adhesive joint. This paper mainly presents the use of these experimental data, to develop a numerical tool to predict the behaviour of adhesively-bonded assemblies. To limit the numerical cost, we propose an approach using joint type elements which allows us to work directly with the relative displacement and the stress. As under elastic assumption, a non uniform stress field is observed in the adhesive joint, an inverse technique has been developed to identify the parameters of the model. For monotonic loadings, a plastic behaviour with isotropic hardening gives good results and allows us to analyse the non-isotropic behaviour of the adhesive with respect to tension-compression. In order to analyse the possibilities of this numerical approach, comparisons with experimental data are presented. A simple lab shear type specimen with thick substrates and beaks is proposed to analyse the influence of different parameters.