Structural Health Monitoring using Carbon Nanotube (CNT) Enhanced Composites

Carbon nanotubes (CNTs) are being investigated as a means for large-scale inspection of composite structures. Several studies have shown that CNTs possess exceptional mechanical stiffness and strength, as well as excellent electrical conductivity and piezoresistivity. Thus, it has been proposed that CNTs could be used not only to reinforce composite structures for improved impact and delamination resistance, but also to enable structures with multifunctional capability. The present investigators have developed advanced fiber-reinforced polymer-matrix laminates with aligned CNTs grown in-situ coupled with a noninvasive sensing method. CNTs have the potential to eliminate problems observed with traditional composite inspection methods that use resistivity due to increased and more reproducible conductivity properties, and offering 3-D electrical continuity to the surface. Results are presented for both through-thickness and inplane resistance, measured using patterned silver-ink electrodes. Lastly, a discussion is presented for the application of guided-wave approaches exploiting the piezoresistive properties of the composites with embedded CNTs.