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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 79
Edited by: B.H.V. Topping and C.A. Mota Soares
Paper 133

Modelling Three-Dimensional Effects in Single-Lap Bonded Joints using Interface Finite Elements

M.F.S.F. de Moura, J.P.M. Gonçalves and P.M.S.T. de Castro

Department of Mechanical Engineering and Industrial Management, Faculty of Engineering, University of Porto, Portugal

Full Bibliographic Reference for this paper
, "Modelling Three-Dimensional Effects in Single-Lap Bonded Joints using Interface Finite Elements", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Seventh International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 133, 2004. doi:10.4203/ccp.79.133
Keywords: bonded joints, interface finite elements, stress concentrations, linear and elasto-plastic analysis.

In this paper, a new model for three-dimensional finite element analysis of adhesive joints is presented. The model includes geometric and material nonlinearities. Its novelty resides in the capability to calculate the stresses across the adhesive layer and at the adherent-adhesive interfaces. This is accomplished by representing the adherents and the adhesive with solid brick elements and the interfaces with special interface elements. The stresses provided by the interface elements are likely to be significant and could not be calculated by the solid elements due to the material discontinuity.

The interface finite element for three-dimensional analysis used in this model was previously developed [1,2]. It consists of eighteen nodes distributed in two faces. The element has zero thickness and is compatible with twenty-seven node isoparametric hexahedral elements available in the ABAQUSRsoftware [3]. The interface element is implemented in the ABAQUSRsoftware through an interface that allows users to implement their own elements.

The use of the model is illustrated with the study of a single-lap joint. Two different analyses were performed. Linear elastic and elasto-plastic material models were considered for the adhesive and adherents. Geometric nonlinearity was considered in all analyses.

The analyses show that, even for a simple geometry such as the single-lap joint, the stresses are three-dimensional. This information is relevant for modelling bonded joints because it demonstrates that two-dimensional models must be carefully used in the strength prediction of adhesive joints.

The use of interface elements allows the calculation of the stresses at the interfaces adherent-adhesive. In this study, it is shown that the peak stresses at the interfaces are much higher than at the middle of the adhesive layer. This observation can explain why the interfaces are critical regions regarding the failure of adhesive joints.

In the nonlinear analysis, the normalized stresses at the interfaces decrease as the load grows. As expected, the plasticization induces a decrease of the stress concentrations in the critical regions.

A more detailed description of the model and analysis of the results are given in [4]. This model has also been successfully used to predict the strength of adhesive joints. That was done using a specific damage model to simulate damage initiation and propagation and their influence in the global structural behaviour. For the details of that analysis, the reader is referred to [5].

M.F.S.F de Moura, J.P.M. Gonçalves, A.T. Marques, P.M.S.T. de Castro, "Modeling compression failure after low velocity impact on laminated composites using interface elements", Journal of Composite Materials, 31, 1462-1479, 1997. doi:10.1177/002199839703101501
J.P.M.Gonçalves, M.F.S.F. de Moura, P.M.S.T. de Castro, A.T. Marques, "Interface element including point-to-surface constraints for three-dimensional problems with damage propagation", Engineering Computations: International Journal for Computer-Aided Engineering and Software, 17, 28-47, 2000. doi:10.1108/02644400010308053
ABAQUS User's Manual, Version 5.6. Hibbitt, Karlsson & Sorensen, Inc., Pawtucket, 1996.
J.P.M. Gonçalves, M.F.S.F. de Moura, P.M.S.T. de Castro, "A three-dimensional finite element model for stress analysis of adhesive joints", International Journal of Adhesion and Adhesives, 22, 357-365, 2002. doi:10.1016/S0143-7496(02)00015-5
J.P.M Gonçalves, M.F.S.F. de Moura, A.G. Magalhães, P.M.S.T. de Castro, "Application of interface finite elements to three-dimensional failure analysis of adhesive joints", Fatigue & Fracture of Engineering Materials and Structures, 26, 479-486, 2002. doi:10.1046/j.1460-2695.2003.00653.x

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