The tensile load bearing capability of adhesively bonded tubular single lap joints which is calculated with the linear mechanical properties of the adhesive is usually much less than the experimentally determined because the majority of the load transfer of adhesively bonded joints is accomplished by the nonlinear behavior of rubber-toughened epoxy adhesive. Also, as the adhesive thickness increases, the calculated tensile load bearing capability with the linear mechanical properties of the adhesive increases, while, the experimentally determined tensile load bearing capability decreases on the contrary.
In this paper, the stress analysis of the adhesively bonded tubular single lap steel-steel joints and carbon/epoxy composite-steel joints under axial tensile load was performed with taking into account the nonlinear mechanical properties and fabrication residual thermal stresses of adhesive. The nonlinear tensile properties of adhesive were approximated by an exponential equation which was represented by the initial tensile modulus and ultimate tensile strength of the adhesive.
The stress distributions in the adhesive were calculated by applying the load obtained from the tensile tests. From the tensile tests and the stress analysis of adhesively bonded joints, the failure model for adhesively bonded tubular single lap joints was proposed.
Using the results of stress analysis, the failure model for the adhesively bonded tubular single lap steel-steel joints and carbon/epoxy composite-steel joints under tensile load was developed, which can be used to predict the load bearing capability of the joint. From the failure model, it was found that the fracture of the adhesively bonded joint was much influenced by the fabrication residual thermal stresses.
As a practical application of the developed adhesive joining theory, in this work, a composite robot structure was designed and manufactured with adhesive joining technology.
After manufacturing the composite arm, the dynamic property and operational performance were compared to those of the hybrid third robot arm that was composed of the aluminum yoke, the composite tubular structure and the aluminum flange.
From the experiments, it was found that the composite third robot arm contributed to improving both the dynamic characteristics and operational performance of the articulated robot.
