PSI - Issue 14

Neelanchali Asija Bhalla et al. / Procedia Structural Integrity 14 (2019) 564–570 Neelanchali et al/ Structural Integrity Procedia 00 (2018) 000–000

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Fig.6 depicts the impact toughness for A-130 and A-150 FS dispersions, at their LSR values. The impact toughness is calculated by computing the area under the stress-strain curve at the limiting strain rate, for the loading part of the stress cycle i.e. till the specimen strain continues to increase with stress. As evident from the figure, the impact toughness for A-130 FS dispersion was found to be double (40 Jm -3 x 10 6 ) than that of A-150 dispersion (around 20 Jm -3 x 10 6 ). 6. Conclusions From the experimental results, following inferences were drawn; 1) As the specific surface area of FS increased i.e. the particle size became finer, the critical shear rate, the severity of shear thickening as well as the magnitude of shear thinning prior to the onset of shear thickening, were found to increase in the low strain rate regime. 2) In the high strain rate regime, the A-130 FS dispersion performed better as compared to A-150 FS dispersion in terms of specimen stress, specimen loading rate and impact toughness. Thus, it can be inferred that the low strain rate and high strain rate shear rheology of FS dispersions may not be similar. A-150 FS dispersion performed better in low strain rate rheological testing exhibiting higher critical shear rate and post shear thickening viscosity whereas in the high strain rate regime A-130 FS dispersion exhibited better response in terms of specimen stress and impact toughness. Due to the fractal structure of FS, it is difficult to comprehend the effect of specific surface area of FS on its low and high shear rate rheologies. Further experimental and numerical studies shall impart a better understanding of the factors influencing the shear thickening behavior of FS dispersions, in the low and high strain rate regimes. Acknowledgements The authors are indebted to IRD-IITD for a grand challenge grant (MI00810) for doing this research project. The authors are also thankful to Chemical Engineering Department, IITD, for assisting in conducting the rheological testing of the samples in their laboratory. The authors also express their sincere gratitude towards the staff of Production Engineering Lab, IITD for extending their full support in the fabrication of SHPB apparatus. References Raghavan SR, Khan, S.A, 1997. Shear-thickening response of FS suspensions under steady and oscillatory shear, J. Colloid Interface Sc. 67, 57 67. Galindo-Rosales FJ and Rubio-Hernandez FJ, 2010. Static and dynamic yield stresses of aerosil©200 suspensions in polypropylene glycol, Applied Rheology 20, 1-10. Sanchez A, 2006. Ph.D Thesis, North Carolina State University. Nandi S, Bose S, Mitra S and Ghosh AK, 2013. Dynamic rheology and morphology of hdpe-FS composites: Effect of interface modification, Polymer Engineering and Science, 53(3), 644-650. S. R. Raghvan HJW and Khan SA, 2000. Rheology of silica dispersions in organic liquids: New evidence for solvation forces dictated by hydrogen bonding, Langmuir 16, 7920-7930. Park J-h, Kim H-g, Han D-h, Lim J-c, Oh D-h and Min K-e, 2007. Rheological behavior of hydrophilic silica dispersion in polyethylene glycol, J. App. Polymer Sc. 103, 2481-2486. Fischer C, Braun SA, Bourban Pe, Michaud V and Plummer CJG, 2006. Dynamic properties of sandwich structures with integrated shear thickening fluids, Smart Materials and Structures, 15 (5), 1467. Zhang XZ, Li WH and Gong XL, 2008. The rheology of shear thickening fluid (STF) and the dynamic performance of an STF-filled damper, Smart Materials and Structures, 17, 035027-035027. Kang TJ, Hong KH and Yoo MR, 2010. Preparation and properties of FS/Kevlar composite fabrics for application of stab resistant material, Fibers and Polymers, 11, 719-724. Khandavalli S and Rothstein JP, 2014. Extensional rheology of shear-thickening FS nanoparticles dispersed in an aqueous polyethylene oxide solution, Journal of Rheology, 58, 411-431. Shan L, Tian Y, Jiang J, Zhang X and Meng Y, 2015. Effects of ph on shear thinning and thickening behaviors of FS suspensions, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 464, 1-7.