Testing of adhesives for bonding of polymer composites

The aim of this project was to select the most suitable epoxy-based adhesive, from three tested, for bonding glass fibre/polyester composites exposed to air at room temperature and 60°C, and cool water. Lap shear specimens (many adhesive-bonded composite assemblies are designated to shear stresses) were tested at room temperature within 1 year. Most commonly used adhesive EPOXY 371 has maintained the shear properties without great changes in all environments, also with other type of primer (P11), and exhibited the best shear strength in cool water. It is recommended for universal usage. Mixed adhesive–cohesive failure in the specimens with increasing part of cohesive failure for joints stored at room and elevated temperature was observed. Adherend was torn up at the joints with LETOXIT LX 012. Joints with this adhesive exhibited the best shear properties at room temperature and 60°C, where damaged adherend area reached up to 80% of the whole bonded area.