Abstract
Piezoresistive properties play a vital role in the development of sensor for structural health monitoring (SHM) applications. Novel stable crack initiation method (SCIM) is established to improve the gauge factor (GF) with maximum achievable working strain region for PI tape enabled buckypaper hybrid sensors. Cracks are generated by applying strain rate-controlled tension force using dynamic mechanical analyzer (DMA). The sensor has been cycled in tension to characterize GF with crack opening. It is determined experimentally that GF increases with increasing crack opening and crack becomes unstable when opening increases above 8 µm. Tremendous improvement in GF has been observed which improved from single-digit to several hundreds. The highest GF obtained so far is ~255, showing 75 times improvement compared with the ones without the SCIM implementation. The crack initiation strain (CIS) is characterized by sonication and centrifugation time. It is determined experimentally that the maximum CIS of 3.5% can be achieved with sonication time of 40 min and increasing centrifuge time has an in-significantly dropping effect on CIS. Excellent stability/reproducibility has been proved/demonstrated on SCIM implemented sensors through a rigorous 12,500 tensile cycle test on DMA. The performance of sensor is practically demonstrated in tension and bending on glass fiber reinforced polymer (GFRP) structures.
Highlights
With both theoretical and experimental evidences, carbon nanotubes (CNTs) inherit excellent mechanical strength, Young’s modulus, electrical and thermal conductivities of approximately 100 GPa1,2, 1 TPa3,4, 3 × 104 S/ cm[5,6] and 2000–3500 W/m·K7,8 respectively
To efficiently generate micro-crack for enhancing the gauge factor (GF) of PI-tape enabled buckypaper based sensor, the stable crack initiation method (SCIM) protocol is developed through which the GF of the sensor is significantly improved from single-digit to several tens and thousands which can be seen in the results of Fig. 1
To compare the results of the change in resistance with and without SCIM implementation, 10 tensile strain cycles are shown in Fig. 1(d), which demonstrates the significance of SCIM implementation to improve the piezoresistive properties of Sensors
Summary
With both theoretical and experimental evidences, carbon nanotubes (CNTs) inherit excellent mechanical strength, Young’s modulus, electrical and thermal conductivities of approximately 100 GPa1,2, 1 TPa3,4, 3 × 104 S/ cm[5,6] and 2000–3500 W/m·K7,8 respectively. To investigate the cause of the properties deterioration and to improve them while maintaining the purity of CNTs, extensive studies have been carried out to study the microstructure of the CNTs and establish a relationship between the parameters of the CNTs and its piezoresistive behavior, electrical and mechanical properties[19,34,35,36,37,38] From these investigations, it can be concluded that the reported properties of the CNT in the bulk form are lagging behind the extraordinary properties of individual CNTs. A well-ordered and covalently linked CNT network is crucial for exceptional properties in the bulk form, but it is very difficult to obtain a well-organized CNT network due to the likelihood of entanglement and bundling during synthesize of buckypaper[17,27]. W. et al used CNT/nylon composites, indicating that the workable strain region decreases from 2% to 1% as pre-stretching increases from 0% to 7%43
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