Thermal and Geometrically Nonlinear Stress Analyses of an Adhesively Bonded Composite Tee Joint with Double Support

Abstract

Carbon fiber reinforced plastics (CFRP) can be successfully joined to metal or composite structural components using the adhesive bonding technique [Semerdjiev, S. (1970). Metal to Metal Adhesive Bonding, Business Books Ltd., London.]. The stress and deformation fields occurring in the adhesive joints due to the thermal loads as well as the structural loads play an important role on the joint strength since the thermal and mechanical properties of the adhesive and adherends are different. Previous thermal stress analyses of the adhesive single-lap joints with simple geometries assumed a uniform temperature distribution through the adhesive joint, consequently predicted uniform thermal strain and stress distributions. In this study, the thermal stress analysis of an adhesively bonded tee joint with double support made of unidirectional CFRP was carried out for variable thermal loading conditions along its outer boundaries and different plate edge conditions. The large displacement and rotation effects were considered using the small strain-large displacement theory. The stress fields in the adhesive layer and the composite members of two tee joints bonded to a rigid base and a flexible plate were investigated. In the thermal analysis, a reference uniform temperature was attributed to all joint members for its stress free state, and air streams with different temperature and velocity were specified along the outer surfaces of the adhesive joint. In addition, the air streams were specified in the vertical or horizontal directions to the composite plates and adhesive layer. The consideration of convective and conductive heat transfer showed that nonuniform temperature distributions occurred in the adhesive tee joints. High heat fluxes took place along the free surfaces of the adhesive fillets at the free ends of the adhesive layers. Geometrical nonlinear stress analyses of two tee joints were carried out using the calculated temperature fields for two different plate edge conditions. Since the adhesive joints consist of materials with different thermal and structural properties, the thermal strains become incompatible along the adhesive layer–plate interfaces. Consequently, the stress concentrations occurred inside the adhesive fillets around the adhesive free ends, and in the regions near the adhesive layer–composite plate interfaces. The adhesive fillets, middle region of the horizontal plate, the elbow sections of the left and right supports appeared as most critical regions of the tee joints. In addition, the support length did not have similar effect of reducing the normal and shear stresses at these critical adhesive and adherend locations.

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