Stress analysis of adhesive joint

Failure of an adhesive joint occurs when the local stress in the bond exceeds the local strength of the materials (i.e., the adhesive or substrate). Theoretically, it should be possible to predict these failures if the strength of the adhesive and the stresses it will endure are known. Emphasis is placed on the strength of the adhesive since most substrate materials are much stronger than adhesives. 

This theory is more complicated than it may seem for three reasons. In order to predict failure of the joint it becomes necessary to know the fundamental properties of the adhesives in bulk form. Measuring properties such as tensile strength and modulus, yield strength, and shear strength is difficult due to specimen fabrication limitations. As mentioned, typical test methods measure properties of the bonded joint rather than just the adhesive s properties. Another complexity arises in the determination of local stresses in the adhesive joint. Stresses typically occur from the application of loads on a system however, deformation of the adherends with respect to the adhesive and stress concentrations in the joint can also produce large local stresses. The last reason for complications is that each joint geometry or design can produce different types of stresses and in different locations. 

This section will not provide a detailed mathematical derivation of stresses in various joint geometries since this could account for an entire book. However, relevant stress theories will be invoked in the discussion while providing a literature review of the subject. Tensile, shear, and peel loadings will be covered since they are the most basic and common in structural adhesive applications. 

This is an extremely complicated subject and will oidy be touched upon here. The ultimate objective is to develop a design method for bonded construction based on the principles of mechanics and rational engineering design so that joint behavior can be predicted. 

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The present discussion has a twofold objective First, to review the literature in the stress analysis of adhesive joints using the finite-element method. Second, to present a finite-element computational procedure for adhesive joints experiencing two-dimensional deformation and stress fields. The adherends are linear elastic and can undergo large deformations, and the adhesive experiences linear strains but nonlinear viscoelastic behavior. Following these general comments, a review of the literature is presented. The technical discussion given in the subsequent sections comes essentially from the authors research(i 2> conducted for the Oifice of Naval Research. 

Groth, H.L., Viscoelastic and viscoplastic stress analysis of adhesive joints. Int. J. Adhes. Adhes., 10, 207-213 (1990). 

Peppiatt, N. A. (1974) Stress analysis of adhesive joints. Thesis, University of Bristol. 

Lunsford, L.R., Stress analysis of bonded joints. Applied Polymer Symposia No. 3, Structural Adhesive Bonding, Presented at a Symposium Sponsored by Picatinny Arsenal and held at Stevens Institute of Technology, September 14-16, 1965, pp. 57-73, Wiley-Interscience, New Yoik, 1966. 

The stress analysis of bonded joints remains in its infancy and, until it is better developed, simple shear strength values such as those given in Figure 2.16 (and typically provided by most manufacturers) should not be used alone to assess the ability of an adhesive to transmit power (see pp.l6 22 Supplementary role of adhesives in power transmission). 

This chapter will discuss the testing, analysis, and design of structural adhesive joints. Adhesive bond test techniques to be considered include tensile, shear, peel, impact, creep, and fatigue. Some considerations will also be given to the effect of environment and test rate. A continuum approach to the analysis of adhesive joints will discuss tensile, shear, and peel stresses which arise in various joint geometries. Classical theories by Volkersen, Goland and Reissner, and others will be included. References to finite element analysis will be made where appropriate throughout the chapter. 

Zou G P and Taheri F. Stress analysis of adhesively bonded sandwich pipe joints subjected to torsional loading. International Journal of Solids and Structures, 43(20), 2006, pp. 5953-5968. 

Hadj-Ahmed R, Foret G and Ehrlacher A (2001), Stress analysis in adhesive joints with a multi particle model of multilayered materials (M4) , IntJ Adhes Adhes, 21(4), 297-307. 

Sharifi S and Choupani N (2008), Stress analysis of adhesively bonded double-lap joints subjected to combined loading . Proceedings of World Academy of Science, Engineering and Technology, July 2008, Vienna, 759-764. 

The stresses in an adhesive joint depend, once a constitutive model is chosen, on the geometry, boundary conditions, the assumed mechanical properties of the regions involved, and the type and distribution of loads acting on the joint. In practice, most adhesives exhibit, depending on the stress levels, nonlinear-viscoelastic behavior, and the adhetends exhibit elastoplastic behavior. Most theoretical studies conducted to date on the stress analysis of adhesively bonded joints have made simplifying assumptions of linear and elastic and/or viscoelastic behavior in the interest of tracking solutions. 

R. D. Adams and N. A. Peppiatt, Stress analysis of adhesively bonded lap joints. Strain Anal. 9, 185-196 (1974). 

M. H. Pahoja, Stress Analysis of Adhesive Lap Joint Subjected to Tension Shear Foroe and Bending Moments T.N.A.M. Report 361, Univeristy of Illinois, Urbana (1972). 

Japanese researchers [18] described a stress analysis of butt joints of steel to aluminium in which joints were assembled with epoxy adhesives and subjected to cleavage loads. They found that the normal and shear stresses were maximised at the edge of the interface on the load application side between the substrates and the adhesive bond. However, both stresses were greater at the edge of the interface between the higher-modulus substrate (steel) and the bond. 

Adams RD, Coppendale J (1977) The elastic moduli of structural adhesives. In AUen KW (ed) Adhesion 1. Applied Science, London, pp 1—17 Adams RD, Coppendale J (1979) The stress-strain behaviour of axially-loaded butt joints. J Adhesion 10 49 Adams RD, Peppiatt NA (1974) Stress analysis of adhesive-bonded lap joints. J Strain Anal 9 185... 

Adams RD, Coppendale J, Peppiatt NA (1978) Stress analysis of adhesive-bonded lap joints. J Strain Anal 13 1... 

Adams RD, Comyn J, Wake WC (1997) Structural adhesive joints in engineering. Chapman and Hall, London Adams RD, Mallick V (1992) A method for the stress analysis of lap joints. J Adhes 38(3-4) 199-217 Adams RD (1989) Strength predictions for lap joints, especially with composite adherends a review. J Adhes 30(l-4) 219-242... 

Adams RD, Peppiatt NA (1977) Stress analysis of adhesively-bonded tubular lap joints. J Adhes 9 1... 

Nakagawa F, Sawa T, Nakano Y, Katsuo M (1999) Two-dimensional finite element thermal stress analysis of adhesive butt joints containing some hole defects. J Adhes Sci Technol 13 309... 

Stress Analysis of Adhesively Bonded Joints Subjected to Impact Loads. 747... 

Daghyani. H.R.. Ye. L. and Mai. Y.W. (1995b). Mode I fracture behaviour of adhesive joints, 2, Stress analysis of constraint parameters. J. Adhesion 53, 163-172. 

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