Composite materials are formed by two or more constituents at macroscopic level. Type and form of fiber plays a vital role in imparting required properties to the composite. Many researchers contributed to the development of artificial fiber composites which are not environmental friendly in nature. Sizable research is also done in the area of natural fiber composites. Human hair is a non-biodegradable waste available in abundant quantity across the world, but is rarely explored for applications in engineering fields. In the present study, a review on behavior of human hair fibers was made to understand their suitability as a reinforcing material in composites. Morphology of the hair fibers is reviewed and the density of the hair fibers was determined using Archimedes principle. Tensile strength of the hair fibers is experimentally estimated. Chemical resistivity and burning tests were conducted. Tensile and flexural properties of hair fiber reinforced polyester composite were experimentally determined and compared.
Sapphire substrates with different orientations have wide applications due to their excellent physical, chemical and optical properties. However, the chemical mechanical polishing of sapphire is challenging due to its chemical inertness, extreme hardness and brittleness. Herein, chemical mechanical polishing of A- and C-plane sapphire was systematically studied using α-Al2O3 and silica abrasives and polishing mechanism was analyzed by X-ray photoemission spectroscopy (XPS) and nanoindentation meter. The high MRR selectivity for C-plane sapphire in α-Al2O3 slurry is the synergy of selective hydration of C-plane and stronger crystal structure of A-plane. The low MRR selectivity for C-plane sapphire in silica slurry can be attributed to the formation of Al2SiO5 on both planes which reduced the impact of strong mechanical effect of α-Al2O3 abrasives. To improve the MRR of A-plane sapphire, a new nanocomposite particle with alumina as the core and silica as the soft shell was prepared by an electrostatic self-assembly method. The new composite abrasives combined the mechanical effect of α-Al2O3 abrasives and chemical effect of silica abrasives and demonstrated substantially higher MRR for A-plane sapphire than pure alumina abrasives, pure silica abrasives and physical mixture of alumina+silica abrasives.
Polymeric-based composites were prepared using chopped fibres of human hair in different volume fractions varying from 5% to 25% by weight and in different fibre lengths ranging from 10 mm to 50 mm. Experiments are conducted to know the tensile strength of the composites. Two-factorfive-level historical data model (DOE) is chosen. In the present study, a mathematical model was developed from the experimental results using response surface methodology (RSM) so as to obtain the optimum tensile strength condition for the composite. The correlation coefficient of the regression model was tested by analysis of variance (ANOVA) to check the adequacy of the mathematical model.
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