"Inkjet-printed Carbon Nanotube Thin Films for Spatial Damage Sensing on Lightweight-designed Structures"
Inkjet-printed Carbon Nanotube Thin Films for Spatial Damage Sensing on Lightweight-designed Structures
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Materials with light self-weight including fiber reinforced polymers (FRPs) and polyurethane/honeycomb sandwich panels are popular in assembling major components of airplanes and vehicles. To accompany the fast development of the lightweight design industry, a reliable, lightweight, and in situ structural health monitoring (SHM) system is needed to monitor real-time structural behavior. In this thesis a multi-walled carbon nanotube (MWNT)-based polymer paint was first developed and improved to perform spatial strain sensing over lightweight structures. To further improve its strain sensitivity, the polymer matrix was replaced by Pluronic-127 to produce more stable MWNT paint solution. In order to further improve the consistency of the carbon nanotube (CNT) thin film, a CNT-suspended ink is developed and inkjet-printed over a flexible substrate. The inkjet-printed CNT thin film consists of a uniform morphology with evenly distributed CNT particles over the entire printed area. Coupled with an electrical impedance tomographic (EIT) method, the CNT thin film is able to reconstruct the conductivity change of itself due to the strain distributions over a tensile tested coupon. In order to gain a more profound understanding of the EIT reconstructions, the elastoresistivity of the inkjet-printed CNT thin film was characterized, correlating its electrical property change with respect to the applied strain state using tensor analysis. It is observed that the EIT reconstruction result shares a similarity with the square root of the determinant of the resistivity matrix. Finally, the inkjet-printed CNT thin film was embedded at the adherend-adhesive interface of a single-lap joint. The testing coupon is tensile loaded to develop an in-plane shear strain distribution at the interface, and the conductivity change over the thin film is reconstructed by EIT. Finite element analyses validate the application as an effective joint monitoring sensor.