Capacitance-based sensor with layered carbon-fiber reinforced polymer and titania-filled epoxy

Abstract

Advances in intelligent infrastructure can be achieved through the use of novel materials for increased systemlevel efficiency and multifunctionality. Carbon Fiber-Reinforced Polymer (CFRP) has been widely used in strengthening, rehabilitating, and retrofitting of existing structures because of its speed of deployment, low maintenance requirement, and high strength-to-weight ratio. In this work, the authors propose a novel method to augment CFRP with self-sensing capabilities. The sensor consists of two CFRP layers separated by a titania-filled epoxy dielectric layer, therefore forming a parallel plate capacitor. Sensing capability can be achieved through variations in the sensor's capacitance provoked by strain, therefore providing an additional function that could be leveraged for structural health monitoring and structural health management purposes. Comprehensive testing, including (1) sensing properties on sensors with and without titania-doped epoxy and (2) electromechanical test on tension specimens subjected to both static and dynamic loading, was conducted. The test results show that doping the titania filler within the epoxy matrix can improve the sensor's sensitivity. The gauge factor is 0.92 under static load and decreases with the increasing frequency up to 1 Hz. Therefore, it can be concluded that CFRP can be used as a self-sensing sensor without affecting its mechanical properties. AbstractAdvances in intelligent infrastructure can be achieved through the use of novel materials for increased systemlevel efficiency and multifunctionality. Carbon Fiber-Reinforced Polymer (CFRP) has been widely used in strengthening, rehabilitating, and retrofitting of existing structures because of its speed of deployment, low maintenance requirement, and high strength-to-weight ratio. In this work, the authors propose a novel method to augment CFRP with self-sensing capabilities. The sensor consists of two CFRP layers separated by a titania-filled epoxy dielectric layer, therefore forming a parallel plate capacitor. Sensing capability can be achieved through variations in the sensor's capacitance provoked by strain, therefore providing an additional function that could be leveraged for structural health monitoring and structural health management purposes. Comprehensive testing, including (1) sensing properties on sensors with and without titania-doped epoxy and (2) electromechanical test on tension specimens subjected to both static and dynamic loading, was conducted. The test results show that doping the titania filler within the epoxy matrix can improve the sensor's sensitivity and that the sensor's signal increases linearly with increasing strain. A static gauge factor of 0.92 was obtained, and the dynamic gauge factor characterized under 0.25, 0.5, and 1Hz. It is also found that CFRP can be used as a self-sensing material without affecting its mechanical properties.

Interlayer Defect Detection in Intra-Ply Hybrid Composite Material (GF/CF) Using a Capacitance-Based Sensor

“…It was found that there was not a big difference between the estimated gauge factor for type-A and -B, which was around 1.3. This gauge factor is relatively high compared with other structural health monitoring systems based on linear capacitive sensors such as 0.92 [31]. A slight difference was observed between the results obtained from samples A-1 and A-2 such as the difference in elastic modulus, which was around 7.4%.…”

Surface textures for stretchable capacitive strain sensors

“…Capacitance-based sensors have been proposed from bio-compatible polymers Burton et al (2019) and nanocomposite thin films Lee et al (2016). Research examples targeting biological skin mimicry for SHM applications include strain sensing sheets based on large area electronics and integrated circuits Tung et al (2014); Zhang et al (2014); Zhou et al (2010), electrical impedance tomography Hallaji et al (2014); Gupta et al (2016), and multifunctional materials Downey et al (2018); Yan et al (2019).…”

Hybrid Flexible NFC Sensor on Paper

“…In particular, strain sensors are intensively investigated for their skin-like features in robotic and prosthetic systems [4], or to detect human motions [5], but are also exploited for structural health monitoring [6]. pH sensors, on the other hand, giving information about the thermodynamics and kinetics of a variety of processes, are fundamental in fields from metabolism and nutrition [7], to catalysis and pharmaceutical chemistry [8], from food manufacturing and processing [9] to environmental science [10].…”