Optimization of inductive fast-curing of epoxy adhesive by model-based kinetics

Abstract

Adhesively bonded joints must be fixed until a necessary degree of cure is reached. This is done by hybrid joining processes or fixing methods that hold the bonded parts in position. Inductive fast-curing can enable time-efficient processes without additional joining methods, but the complexity of the process and the variety of influencing factors make it challenging to develop. In this work, a new approach to the design of fast-curing processes is pursued, which, in addition to classical temperature measurements, relies on real-time simulation of the curing degree, providing direct feedback on the quality of the induction parameters set. DSC measurements were performed on a single-component epoxy adhesive, which were used to develop kinetics models according to model-free and model-based methods. Fast curing tests show the dependence of initial strength on temperature and degree of conversion, with a comparison of experimentally and numerically determined degrees of conversion revealing high agreement. The demonstrated suitability of the kinetics model allowed fast-curing processes to be optimized using a developed tool for real-time conversion degree determination, such that a high initial strength was achieved even with different joining part materials. FEM simulations also reveal the effect of temperature gradients due to uneven heating, which leads to conversion gradients in the adhesive layer that must be avoided.