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.

Modeling of a cracked and repaired Al 2024T3 aircraft plate: effect of the composite patch shape on the repair performance

“…Thus, several works have been devoted to such a type of degradation, among them can be cited the use of the zone damaged theory to explain the disbonding mechanisms due to the adhesive ruin. This theory is based primarily on the formation and development of a damaged zone, then on the crack propagation initiated in this zone, having reached a critical size, under more intense loads [23]. Crombr [24] and al, Sheppard [25] and al, have developed a model for predicting damage of the adhesive layer.…”

Stress analyses of composite tee joints at elevated temperature

“…Kumari and Sinha [13,14] investigated the effects of moisture and temperature on the behavior of composite tee joints made of carbon fiber composite materials using finite element methods. Apalak and Gunes [15,16] investigated thermal and geometrically nonlinear stresses of an adhesively bonded composite (CFRP) tee joint with double support, and Apalak et al [17] investigated nonlinear thermal stresses in an adhesively bonded steel single lap joint. Kadioglu et al [18] studied the stresses of a single lap joint experimentally and numerically at 22, 60, and 90°C, and they found that the strength of adhesive joints increased with the increase of temperature, which is opposite to the conventional beliefs.…”

Effect of the angles of the cracks of corroded plate in bonded composite repair

“…For the epoxy adhesive (FM 73), it has been shown that the ratio of the damaged area corresponding to the failure of this adhesive is 0.247. Apalak et al [18] used the damaged zone theory to analysis of the effects of thermal stresses in the glue joint. They showed that damage can be expected in composites as well as in the adhesive when using soaked adhesives.…”