Fabrication of Calotropis Gigantea fibre reinforced compression spring for light weight applications

A new attempt has been made in the manufacturing of helical springs, using Calotropis Gigantea fibre as the raw material. Calotropis Gigantea (CG) is a tropical shrub plant with high seasonality and naturally high yield; its fibre is extracted from the stem of the plant and rendered in a twisted form. Twisted fibre is treated with NaOH to address the major drawback associated with this natural fibre; its hydrophilicity. The treated fibre is then dipped in to a matrix, and turned into a spring in the lathe, using a shock absorber spring as a die. The spring is tested and the basic properties are analysed; the performance as a function of NaOH treatment is duly evaluated. The stiffness and shear modulus value increases slowly and reaches 1 N/mm and 1.28 GPa, with 4 wt% NaOH based alkali treatment. The results obtained are rationalized Finite Element Analysis as well; it is shown that the material may be considered to isotropic in the transverse direction, when under axial loading (as on the surface of the fabricated coil).