We report highly sensitive and reliable strain sensors based on silver nanoparticle (AgNP) and carbon nanotube (CNT) composite thin films. The CNT/AgNP was prepared by a screen printing process using a mixture of a CNT paste and an AgNP ink. It is discovered that the sensitivity of such sensors are highly dependent on the crack formation in the composites. By altering the substrate use and the relative ratios of AgNPs and CNTs, the formation and propagation of cracks can be properly engineered, leading to piezoresistive strain sensors with enhanced sensitivity and robustness.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1626-z) contains supplementary material, which is available to authorized users.
Triboluminescent (TL) materials are assessed as components in structural health monitoring (SHM) systems within polymer composites. Processing must be addressed due to particle characteristics such as density, morphology, and chemical makeup, all of which can affect polymer curing dynamics and thermo-mechanical properties. This study considers key processing parameters during incorporation of TL compounds into various polymers. The TL materials chosen for this study are zinc sulfide manganese (ZnS:Mn) and europium dibenzoylmethide triethylammonium (EuD 4 TEA). These crystals are dispersed within the liquid phase of polyvinyl ester (VE), polydimethylsiloxane (PDMS), and Dymax 9663 ultraviolet-curable (UV-curing) resins. Incorporation of the europium compound apparently slows the cure process, particularly in the UV-curing resin, while the zinc compound had a minimal effect on curing. Tensile testing shows a decrease in tensile modulus due to incorporation of TL crystals. Incorporation of the europium compound caused a 20-53% decrease in modulus; incorporation of the zinc compound caused a 7-66% decrease in modulus. Experimental results are used to create a multi-scale model using Digimat. Discrepancies in the found values may be due to sample quality (e.g. presence of voids in experimental samples).
External bonding with fiber-reinforced polymers is currently one of the most popular technologies for rehabilitation of concrete structures. However, the effectiveness of the technology largely depends on the strength of the bond between the fiber-reinforced polymer laminate and the concrete substrate. This article provides a system to monitor the loss of bond between the fiber-reinforced polymer laminate and the concrete. Fiber optic sensors are broadly accepted as a structural health monitoring device for fiber-reinforced polymer materials by integrating the sensors into the host material. A recent development in fiber optic sensor technology is the mechanoluminescence-based optoelectronic sensors. Concrete beams strengthened with multifunctional fiber-reinforced polymer laminates were tested in shear using these sensors to evaluate the bond strength of the composite system. The sensors showed response to shear stress transfer in the adhesive layer which was observed to be as low as 2 MPa. The inclusion of sensors does not affect the bond strength (3.35 MPa), for both beams with sensors and without sensors. Real-time failure detection of fiber-reinforced polymer–strengthened beams was successfully achieved in this study. In future, the scheme aims at providing a tool to reduce the response time and decision making involved in the maintenance of deficient structures.
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