Mechanical and dynamic properties of nettle-polyester composite

This work deals with the use of Himalayan Nettle (a natural plant fiber) as a reinforcement in polyester resin matrix and characterisation of as-formed nettle-polyester composite. Tensile test on single nettle fibers revealed that the Young's modulus and tensile strength decrease with increase in fiber diameter, and chemical composition test results show that the fiber has higher content of cellulose, hemi-cellulose and lignin that result in better mechanical, biodegrading and thermal stability properties of the composite respectively. Characterization of mechanical properties of randomly-oriented short himalayan nettle fiber reinforced-polyester resin matrix composite was done using tensile, compression and flexural test results. New analytical models were developed considering the effects of orientation and variation of fiber diameters for the determination of Young's modulus and tensile strength. The models are found to yield results which are in good correlation with experimental results. Experimental modal analysis was carried out on cantilever beam specimens for determining material and material plus structural damping ratios using half power band-width method. At higher frequencies, the average damping ratios were found to be 4 to 10 times higher than polymer concrete, C.I. and steel materials. Morphological analysis of the composite (SEM) revealed the structure of the nettle fiber to be hollow, which helps to improve specific stiffness and vibration absorption ability.