An innovative testing technique for assessing the VHCF response of adhesively bonded joints

In the last few years, the use of adhesive joints for structural applications has rapidly increased and adhesives are more often subject to fatigue loads during their in-service life. In presence of a rapidly varying load, such as a high-frequency vibration, adhesively bonded joints may undergo fatigue lives in the Very High Cycle Fatigue (VHCF) region that are significantly larger than those investigated in usual high-cycle fatigue tests. The present paper proposes an innovative testing technique for performing accelerated fully reversed tension-compression VHCF tests on adhesive butt-joints. The procedure for the design of the adherends is described and then experimentally validated. Ultrasonic VHCF tests are finally carried out on a cyanoacrylate butt-joint up to 10(9) cycles: experimental results show that the proposed testing equipment permits an effective assessment of the VHCF response of the adhesive in a limited testing time.