Graphene nanoplatelet (GNP)/poly(methyl methacrylate) (PMMA) nanocomposite solution was spray coated on a glass fibre reinforced polymer composite (GFRP) beam with different initial electrical resistance (R 0 ). Scotch tape erosion method was used to tailor the R 0 of the sensors. Beams and the sensors were characterized by computed tomography (CT) and scanning electron microscopy (SEM) respectively. The piezoresistive behaviour of these sensors was evaluated in monotonic, step and cyclic loading conditions. These spray coated sensors offered good sensitivity (38.5 times) as compared to a strain gauge. A gauge factor (GF) of 55±0.5, 70±2, and 77±1 was obtained for R 0 of 1, 7 and 21 kΩ GNP layers, respectively. Sensors showed good response and stability under the step and cyclic loading conditions. The ease in the process of application coupled with good sensitivity demonstrates that the GNP/PMMA spray coated sensor can be a potential candidate for the futuristic multi-functional materials for structural health monitoring.

In this study, we have extracted bioactive compounds from seabuckthorn (SBT) leaves. Total flavonoid content of SBT leaf extract estimated as rutin equivalent was found to be 116.98 AE 3.06 mg/g of extract. Further, we pre-treated aramid (Nomex IIIA) fabric with triethylene tetramine to increase the wickability of the fabric for better extract uptake. Surface etching on the amine treated fabric morphology was determined by scanning electron microscope analysis. Then, SBT leaf extract was coated using citric acid as cross-linking agent on to aramid fabric by pad-dry-cure method for improved wash durability. Universal attenuated total internal reflection Fourier transform infrared characterization of the SBT coated fabric showed distinct hydroxyl peak at 3305 cm À1 , carbonyl peak at 1728 cm À1 , and -C-O-C peak at 1083 cm À1 . There was no significant difference in the char produced by SBT coated fabric and control samples as estimated using flammability tester. Antimicrobial activity of the SBT coated fabric was assessed by both qualitative (agar diffusion method) and quantitative (percentage reduction test) methods using test organisms. An inhibition zone for Escherichia coli and Staphylococcus aureus was found to be 10.2 mm and 12.3 mm, respectively, by agar diffusion method. Quantitative assessment by percentage reduction test showed a reduction percentage of 96.00% and 93.00% for S. aureus and E. coli, respectively. Results suggested that SBT might be a valuable ingredient for the development of antimicrobial aramid textiles.

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Abstract. Graphene-polymer nanocomposite films show good piezoresistive behaviour and it is reported that the sensitivity increases either with the increased sheet resistance or decreased number density of the graphene fillers. A little is known about this behaviour near the percolation region. In this study, graphene nanoplatelet (GNP)/poly (methyl methacrylate) (PMMA) flexible films are fabricated via solution casting process at varying weight percent of GNP. Electrical and piezoresistive behaviour of these films is studied as a function of GNP concentration. Piezoresistive strain sensitivity of the films is measured by affixing the film to an aluminium specimen which is subjected to monotonic uniaxial tensile load. The change in resistance of the film with strain is monitored using a four probe. An electrical percolation threshold at 3 weight percent of GNP is observed. We report non-monotonic piezoresistive behaviour of these films as a function GNP concentration. We observe an increase in gauge factor (GF) with unstrained resistance of the films up to a critical resistance corresponding to percolation threshold. Beyond this limit the GF decreases with unstrained resistance.

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