Sensing Capabilities of Carbon Nanotube Reinforced Adhesive Films in Joints with Dissimilar Materials: An Approach from Coupon to Sub-element Level

Abstract

This work aims to investigate the crack propagation monitoring capacity of carbon nanotube (CNT) reinforced adhesive films in joints with dissimilar materials. To achieve this purpose, Mode-II standard tests have been carried out while the electrical response has been determined in terms on electrical resistance measurements. It has been observed that electrical and mechanical response show a good agreement, with an increase of the electrical resistance with crack length due to the breakage of electrical pathways. Brushed and grit-blasted metallic substrates were tested and some significant differences between electrical response have been observed. Samples with poorer surface treatment showed a more unstable response due to a continuous creation and breakage of electrical pathways while grit-blasted specimens present a uniform electrical resistance increase. These results were also stated by microstructural analysis, showing the presence of weak areas in case of brushed substrates. In addition to that, skin-stringer elements were also tested at static conditions, showing a good electrical continuity. Therefore, the potential and applicability of the proposed technique for SHM of bonded joints have been demonstrated