Monitoring of crosslinking of a DGEBA-PAMAM adhesive in composite/aluminium bonded joint using mechanical and ultra-sound techniques

Adhesive cure is an important and determining aspect of strength and stability of bonded structures. Crosslinking of the polymer leads to the adhesive strength, stiffness and durability. Depending on the resin and curing agent used, cure time can vary from minutes to weeks, even then 100% crosslinking not being guaranteed. Standard methods based on dynamic mechanical analysis (DMA) or calorimetric techniques (DSC, DTA) are valuable tools for evaluating short curing times. However, they are devoted specifically to the polymers alone, and not in situ in adhesive joints. In this contribution, we have analysed composite—aluminium joint bonded with a slow-curing DGEBA-PAMAM adhesive system with two new, non-destructive methods. The first is based on measurements obtained from strain gauges mounted on one bonded adherend. The second uses an ultrasound technique based on the through transmission method. Both methods point to the same curing kinetics. Contrary to the classic curing time evolution methods, they are directly applied to adhesive joints where the polymer is only one of the constituents.