Nonlinear analysis of bonded joints with thermal effects

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Virginia Polytechnic Institute and State University

A numerical analysis of the nonlinear response of bonded joints is presented. Mechanical and thermal loadings are considered. Material stress-strain response is represented by Ramberg-Osgood approximations. Temperature-dependent properties including modulus percent retentions and coefficients of expansion are modeled with linearly segmented curves. Bonded joints with graphite-polyimide, boron-epoxy, titanium, or aluminum adherends are analyzed using a quasi 3-dimensional finite element analysis. In adhesively bonded joints, the adhesives considered are Metlbond 1113 and AF-126-2.

Elastic results are presented for single and double lap joints, with and without adhesives. It is shown that mechanically induced stresses are greatly affected by longitudinal adherend stiffness. The effects of adherend transverse stiffness are shown to be significant in some cases. Residual curing stresses are shown to be significant in all joints except those with similar adherends and no adhesive.

Nonlinear results are presented for adhesively bonded joints. It is shown that adhesive nonlinearities are only significant in the predicted adhesive shear stresses. Adherend nonlinearities and temperature-dependent properties are shown to have little effect upon the adhesive stress predictions under mechanical and thermal loadings.