Load rate effects in adhesive single lap joints bonded with epoxy/ceramic composites

Abstract

The present paper is concerned with the analysis of the effect of the loading rate in a particular class of single lap joints used in the oil industry. The adhesive/adherend system consists of ASTM A36 steel plates bonded with an epoxy/ceramic composite. The loading rate sensitivity is analysed considering two different situations: (i) strain controlled quasi-static rupture tests and (ii) applications in which the joint may oscillate like a spring. This second situation is motivated by a specific application: the transport of an ethanol reservoir by a crane using a special truss lifting system attached to the tank through bonded joints. Quasi-static tensile tests allow observing a rate-dependent behaviour of the joint with higher strengths for higher cross-head velocities. An algebraic equation is proposed to predict the dependence of the rupture force on the elongation rate in tensile tests and the model predictions are in good agreement with experimental results. However, in the case of the transport of a tank with mass M (situation (ii)), the lifting system cannot be only designed to resist the static load (the weight). Fast loading may induce vibration. Like in a spring-mass system, even a very small oscillation of the joint induces a dynamic load that is higher than the static load. A simple analysis allows proposing conditions for a safe operation in this case.