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Computational Models of Adhesively Bonded Joints
Linköping University, Department of Management and Engineering, Mechanics . Linköping University, The Institute of Technology.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Simulations using the Finite Element Method (FEM) play an increasingly important role in the design process of joints and fasteners in the aerospace industry. In order to utilize the potential of such adhesive bonding, there is an increasing need for effective and accurate computational methods. The geometry and the nature of an adhesive joint are, however, not so simple to describe effectively using standard FEM-codes. To overcome this difficulty, special FEM-elements can be developed that provide a material surface treatment of the adhesive and the joined parts.

In order to create a model that reflects the above features, one may introduce proper scalings on the geometry and on the material properties in terms of a perturbation parameter. Within the framework of three-dimensional elasticity, together with an asymptotic expansion method, a material surface model is obtained through a systematic procedure. In such a derivation, no a priori assumptions for the displacements or stress fields are needed. The final result is a variational equation posed over a single reference surface which forms the basis of a structural element for the compound joint.

Through the usage of continuum damage mechanics and the framework of a generalized standard material, the linear elastic model is extended to include an elastic-plastic material model with damage for the adhesive. The model is FE-discretized and an important implication is that the (quasi-static) propagation of the local failure zone in the adhesive layer can be simulated. The failure load is obtained as a computational result and consequently no postulated failure criterion is needed. The derived FE-method opens up the possibility to efficiently model and analyze the mechanical behavior of large bonded structures.

Place, publisher, year, edition, pages
Institutionen för ekonomisk och industriell utveckling , 2007. , 32 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1076
Keyword [en]
adhesively bonded joint, asymptotic expansion, finite element, damage mechanics
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-10195ISBN: 978-91-85715-61-9 (print)OAI: oai:DiVA.org:liu-10195DiVA: diva2:16955
Public defence
2007-03-16, C3, Hus C, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Note
At the time the thesis was defended paper I. was in fact two manuscripts, which later were combined to give the published article.Available from: 2007-11-16 Created: 2007-11-16 Last updated: 2017-05-15
List of papers
1. Modelling of adhesively bonded joints by an asymptotic method
Open this publication in new window or tab >>Modelling of adhesively bonded joints by an asymptotic method
2008 (English)In: International Journal of Engineering Science, ISSN 0020-7225, E-ISSN 1879-2197, Vol. 46, no 12, 1291-1324 p.Article in journal (Refereed) Published
Abstract [en]

To utilize the potential of adhesive bonding, there is an increasing need for effective and accurate computational methods. The geometry and behaviour of an adhesive joint is, however, not so simple to model effectively by regular finite elements. The main reason is that the very thin adhesive layer with a low Youngs modulus must be modelled by a large number of finite elements in the thickness direction to achieve sufficiently accurate calculations. To overcome this difficulty, a material surface treatment of the adhesive and the joined parts can be attempted. This paper concerns the derivation of such a model by introducing scalings on the geometry and on the material properties in terms of a perturbation parameter. Within the framework of three-dimensional elasticity, together with an asymptotic expansion method, a family of limit models are obtained through a systematic procedure. in such a derivation no a priori assumptions on the displacements or stress fields are needed. The final result is a variational equation posed over a single reference surface. In regions near the boundary of the joint a boundary layer phenomena occurs. This indicates that the asymptotic series needs to be complemented by additional terms, in order to satisfy all boundary conditions. A structural model including shear- and peel deformation is finally proposed which improves the solution close to the boundary.

Keyword
Adhesively bonded joints, Asymptotic expansion, Surface description
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-16351 (URN)10.1016/j.ijengsci.2008.06.008 (DOI)
Available from: 2009-01-16 Created: 2009-01-16 Last updated: 2010-12-03
2. Analysis of Adhesively Bonded Joints: A Finite Element Method and a Material Model with Damage
Open this publication in new window or tab >>Analysis of Adhesively Bonded Joints: A Finite Element Method and a Material Model with Damage
2006 (English)In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, Vol. 66, no 8, 1271-1308 p.Article in journal (Refereed) Published
Abstract [en]

This paper deals with the derivation of a finite element (FE) method for an adhesively bonded joint which consists of two relatively thin bodies, joined by an even thinner adhesive layer. It is based on a model of the compound joint where the three bodies involved are described as material surfaces. A geometrically two-dimensional model, where the middle surfaces of the upper and lower body are represented as geometrically coinciding surfaces, is obtained.An elastic-plastic material model with damage is used for the adhesive layer, and an important implication is that the (quasi-static) propagation of the local failure zone in the adhesive layer in a structure can be simulated. Consequently, the failure load is obtained as a computational result and no failure criterion is needed.The problem is discretized, and a surface model, where only a single surface needs to be FE-meshed, is obtained. A single-lap joint is analysed and good agreement is obtained when compared to an analysis using a fine mesh with brick element. Furthermore, the failure load is computed and compared with experiments.The derived FE method opens up the possibility to efficiently model and analyse the mechanical behaviour of large bonded structures.

Keyword
adhesively bonded joint, finite element, damage mechanics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-12741 (URN)10.1002/nme.1593 (DOI)
Available from: 2007-11-16 Created: 2007-11-16 Last updated: 2009-06-04
3. Analysis of Adhesively Bonded Structures: A Finite Element Method and Failure Simulations using a Material Model with Damage
Open this publication in new window or tab >>Analysis of Adhesively Bonded Structures: A Finite Element Method and Failure Simulations using a Material Model with Damage
2007 (English)Article in journal (Refereed) Submitted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-12742 (URN)
Available from: 2007-11-16 Created: 2007-11-16 Last updated: 2010-04-28

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