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In the structural applications, the composite material employs a significant contribution in various industrial applications. In this paper, the experimental nonlinear viscoelastic behavior, tensile and flexural strength properties are analyzed in aloevera /hemp/flax natural fiber sandwich laminate composites (NSLC) with the addition of barium sulfate filler. The dynamic mechanical properties such as storage modulus (E′), loss modulus (E″) and damping factor (Tan δ) are analyzed using dynamic mechanical analyzer as a function of temperature and frequency. The homogeneity, crosslink between the fiber and the matrix of the natural fiber sandwich laminate composite samples are analyzed by a cole-cole plot and complex modulus models. The improvement in flexural strength is observed in the NSLC4 sample (138.34 N/mm2), but the addition of barium sulfate affects the tensile strength (28.8 N/mm2). From the dynamic mechanical analyzer, it is observed that the storage modulus (E′) at the glassy region in the NSLC2 sample is 19.9% whereas in the NSLC4 sample it is 15.57%. Further, the addition of barium sulfate filler enhances the loss modulus (E″) by 28% in NSLC4 sample. The NSLC4 sample shows the better homogeneity in the cole-cole plot and high crosslink between the fiber and the matrix is observed from the complex modulus.

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The residual stress was predicted through a model of the multi-pass girth weld joint using Finite Element Method (FEM). Coupled Thermo-Metallurgy-Mechanical (TMM) analysis was carried out and the predicted final residual stress was compared with experiment data. To study the role of aged martensite in final residual stress, two models were simulated and discussed: models with and without aged martensite (prime martensite only). Comparing the experiment data, the model with aged martensite has shown closer prediction while the one without the aged martensite has over predicted the residual stress.

Vibrations transmitted into the machine tool structure made of cast iron cause chattering and develop positional errors between the components during machining operations, causing dimensional inaccuracy and poor surface finish for the products manufactured from them. As an alternate material for cast iron, mineral cast epoxy granite structures are found to exhibit good mechanical properties such as high stiffness and damping ratio at a lesser weight. This study attempts to fabricate an epoxy granite lathe bed having same stiffness as that of a cast iron microlathe bed, and the dynamic characteristics of both the beds are compared. The dimension for the epoxy granite bed is obtained through analytical and finite-element method analysis such that it has same stiffness as that of a cast iron microlathe bed. Modal analysis is conducted to determine the dynamic characteristics of the lathe fabricated. It is found that the damping ratio is improved by 2.2 times for the fabricated epoxy granite bed. In addition, a weight reduction of about 38.64% is observed for the epoxy granite lathe bed in comparison with same-stiffness cast iron bed. To verify the dimensional stability of the fabricated epoxy granite bed, oil and water immersion tests are conducted on test specimens and no change in the dimensions is observed. It is observed that epoxy granite is a promising alternative material for fabrication of advanced machine tool structures.

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