Damage sensing of adhesively-bonded hybrid composite/steel joints using carbon nanotubes

Carbon nanotube networks have been used previously for in situ sensing of matrix damage in fiber-reinforced composites. In this research, the ability of carbon nanotube networks to sense and distinguish different types of damage in adhesively-bonded hybrid composite-to-metal joints is evaluated. Toward this end, conductive networks of carbon nanotubes are introduced to the composite substrate as well as the epoxy adhesive. By altering the geometry and chemically treating the steel substrate surface, different failure mechanisms of the single-lap shear joints are achieved. It is demonstrated that these failure mechanisms each possess a distinct resistance response, therefore proving the ability to not only sense failure in situ, but also to distinguish the extent and nature of damage which occurs.