Colloquia

Samenvatting

Adhesive joints are widely used in high-precision mechanical systems as an alternative or complement to mechanical connections, offering efficient load transfer and design flexibility. One of these applications is the Machine Support Frame (MSF) from MECAL-HTS, which supports the next generation of ASML chip machines all around the world. The epoxy adhesive is applied as discrete circular disks (or dots) between the steel and concrete components / floor to avoid crack propagation through the entire adhesive joint at once. The MSFs are often installed in areas with seismic events which are dynamic and stochastic, making their numerical simulations rather complicated and slow. Therefore, building codes like ASCE 7 and Eurocode 8 have established, semi-empirical procedures for an equivalent static method to simplify the dynamic and stochastic seismic events into a set of static lateral forces. Based on this equivalent force, the resulting motion of the MSF creates high tensile stresses at the concrete-epoxy joint and causes tensile failure of the concrete. Failure of a single dot can lead, in some cases, to complete failure of the adhesive joint and therefore the MSF.

This work evaluates a stress- and strain-based failure criteria for predicting tensile failure of a single adhesive dot joint with the help of controlled experiments through a dedicated test setup and Finite Element simulations. Additionally, the response of a row of epoxy dots is assessed post-failure of the first dot.  The results show that a strain-based criteria can be used to predict concrete failure, and that the failure behaviour of a row of dots depends on the load type. This work provides a generic methodology for assessing the behaviour and failure of adhesive joints in diverse engineering applications, where adhesives are glued to concrete.