Robust Metal to Composite Hybrid Bonded Joint

A new method to analyze hybrid metal to composite bonded joints was developed using a fracture mechanics approach. The approach evaluates the strain energy release rate and mode mix associated with adhesive crack and disbond at the joint fitting tip. Several different fitting geometry tips and bond thickness were analyzed and compared to identify robust joint fitting tip features. The comparison shows what is suggested as good features to optimize adhesive bond strength may actually be detrimental to a hybrid metal to composite joint. This is due to the weakest link shifting from the adhesive for metal joints to the adhesive to composite interface for metal to composite joints. The analysis results indicate a robust metal to composite joint should have features that minimize the total strain energy release rate and mode I open contribution under loading conditions.