Using an embedded Buckypaper to monitor mode I crack growth in bonded joints

Structural Health Monitoring (SHM) systems are commonly integrated in bonded joints for different applications in order to detect and predict potential fatigue and damages caused by internal and external agents they are subjected to during their operation life. However, each of the current SHM systems presents some drawbacks, as the reduction of structural properties or the difficulty in its implementation. This work deals with the use of a Carbon Nanotube film (Bukypaper) as a sensor in double cantilever beam (DCB) bonded joint specimens for crack growth monitoring purposes. Buckypaper (BP) sheets were manufactured and integrated in adhesive film layers and its integration quality was studied by Scanning Electron Microscopy (SEM). The effect of the integration of different thickness BPs in the mechanical performance of the bonded joints was also assessed performing DCB fracture tests. Also, electro-mechanical tests were conducted using the BP as the sensor, monitoring the output in the electrical resistance during the crack propagation. It was observed the capability of BP to detect and locate the damage during the test with a linear dependence between the electrical resistance measured in the BP and the deduced crack growth, proving the potential of the BP to monitor self-sensing bonded joints.