Browsing by Author "Mohan Kumar, T.S.M."

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Alkali absorption and durability studies on CFRP laminated composites
(American Institute of Physics Inc. subs@aip.org, 2020) Mohan Kumar, T.S.M.; Krishna, M.; Joladarashi, S.; Kulkarni, S.
Fiber Reinforced Plastics (FRP) are widely used in marine, aeronautical, automotive, space applications due to their corrosive resistance and low cost to performance. The main aim of this research was to examine the impact of alkali absorption and durability in the Carbon/Epoxy, Carbon/Vinylester, and Carbon/Isopolyester composites immersed in 13.59 pH alkaline solutions for a maximum of 25 days at 27Â°C (room temperature) and 65Â°C. Epoxy, vinyl-ester and Isoployester resin are selected as a matrix material and Poly-acrylonitrile-based Carbon fiber of 200 gsm fabrics is chosen as reinforcement and hand lay-up process is used for fabrication in the ratio of 35: 65 respectively and cured at room temperature with applied pressure using hydraulic press for 24 hrs. Solution of alkali was prepared and specimens were subjected to alkali solution. The moisture absorption was calculated on the basis of rate of moisture for every 5days interval and rate of diffusion coefficient (m2/sec) were calculated. Similarly durability studies (UTS, ILSS and FS) are conducted at 27Â°C and 65Â°C. Characterization of the fractured area was done using a scanning microscope. The obtained result rate of moisture absorption in case of neat casting and CFRP specimen shows the maximum alkali absorption in Iso-polyester / carbon whereas the minimum absorption was shown in vinyl ester/carbon specimens at RT and at 65Â°C over a period of 25days. At room temperature and 65Â°C the diffusion coefficient (D) was found and identified higher value for Iso-polyester/carbon and low for vinyl ester/carbon this is because Iso-polyester are distributed along the main chain, which makes easily available for reaction but in vinylesters the ester functional groups acts as a shield by methyl groups which restrict the easy absorption. Reduce in percentage in mechanical properties is due to Alkali absorption in terms of reduced degradation values in UTS, Flexural Strength and ILSS samples, carbon / epoxy showed supremacy over vinylester / carbon and iso-polyester / carbon. Scanning electron microscopy images show the embrittlement and micro-cracks on surface due to exposure to the alkali environments, matrix bonded to fiber are hardly identified as the temperature increases. Â© 2020 Author(s).
Comprehensive review of modeling and material selection for hybrid sandwich composites for ballistic impact application using Six Sigma DMAIC methodology
(SAGE Publications Ltd, 2025) Mohan Kumar, T.S.M.; Joladarashi, S.; Kulkarni, S.M.
Natural fiber-based PMC (polymer matrix composites) have recently been increasingly popular because of their reduced product weight, low material costs, and renewable sources. Hybrid composites with different combinations of fibers/matrix are attracting interest from many manufacturing industries and researchers for various applications because of their specialized mechanical and impact properties. Hybridization is one of the most essential and indispensable strategies to improve composite material performance. Hybrid sandwich composites are reviewed to enhance the mechanical properties. They mainly concentrate on improving impact properties with increased energy absorption and penetration behavior, making them competent for advanced applications. The most time-consuming and challenging task is identifying the suitable composite material for a specific application. Selecting a suitable fiber and matrix is a difficult job for impact applications because the impact can cause severe damage to composite used in structural applications. The main objective of this review is to select suitable fiber and matrix combinations for impact application by exploring the literature gap. The Six Sigma DMAIC methodology provides a different approach to the selection of material. The benefit of this methodology is the choice of material has been made based on a twofold decision-making process that provides an accurate result. In addition to this blending, the qualitative approach (Pugh method) and the quantitative approach (Analytical hierarchy process) produce more accurate results during the comparison process, making it easier to choose the best material. © IMechE 2025.
High-Velocity Impact Behavior of Sandwich Composite with Compliant Skin and Sea Sand Strengthened Functionally Graded Core: Experimental and FE Approach
(Korean Fiber Society, 2025) Mohan Kumar, T.S.M.; Joladarashi, S.; Kulkarni, S.M.; M, V.
The present study investigates optimizing the impact resistance of novel functionally graded sandwich composites using numerical and experimental approaches. The high-velocity impact (HVI) behavior of functionally graded core sandwich composite (FGCSC) with bio-based jute/natural rubber skin and epoxy/sea sand (varying sea sand percentage 0, 10, 20 and 30%, and varying core thickness 10, 20, and 30 mm) functionally graded core. High-velocity impact (HVI) tests are performed using gas gun equipment at an impact velocity ranging from 200, 275, and 350 m/s. The weight residual and burnout method were used to test the gradience of core; both techniques showing significant correlation, and the variance in gradation could be observed. For FE analysis, the FGCSC are represented as deformable bodies, and the bullet is defined as a rigid body using commercially available dynamic explicit software. The HVI test results show that the proposed FGCSC has higher energy absorption capabilities, with core thicknesses of 30 mm and sea sand composition of 30%, resulting in a 1.80% improvement in energy absorption. A finite element study is also carried out to correlate the results, and the obtained results are in better agreement with the experimental findings. The damage analysis indicates that the developed FGCSC with flexible face sheets results in better damage mitigation. The findings suggest that FGCSCs are highly effective for bullet-proofing applications, including personal protective gear and structural components in defense. Further study and optimization could enhance the applicability of these sandwich composites in various protective and structural uses. © The Author(s), under exclusive licence to the Korean Fiber Society 2025.
Influence of sea sand reinforcement on the static and dynamic properties of functionally graded epoxy composites
(Springer Science and Business Media Deutschland GmbH, 2024) Mohan Kumar, T.S.M.; Joladarashi, S.; Kulkarni, S.M.; Doddamani, S.
This study aims to study the static and dynamic properties of the functionally graded epoxy composites with sea sand particles as reinforcement. In this study, functionally graded polymer composites (FGPC) were fabricated by dispersing sea sand throughout the epoxy, exhibiting a spatially varying composition profile within the material. Physio-mechanical properties and high strain rate compression responses were determined for the prepared FGPC by varying the composition of sea sand [0%, 10%, 20%, and 30% (by weight)]. The gradience analysis was performed using the burn-out test and weight method, and the results significantly matched, as well as the variation in gradation could be identified. The density and void content are increased with increased sea sand composition. Tensile and specific strength for neat epoxy shows a 2.41 times increase compared to 30% sea sand-filled epoxy. When loaded from the composite side of FGPC, flexural strength increased by 27.93%, hardness increased by 12.47%, and impact strength increased by 2.35 times for 30% sea sand-filled epoxy compared to neat epoxy. Under dynamic compression loading, FGPC was subjected to split-Hopkinson pressure bar experiments for neat and filled epoxy. These samples were deformed at strain rates in the 103 s?1 while subjected to pressures of 2, 3, and 4 bar. Stress–strain curves and the strain rate were computed using the raw data. High strain rates improve compressive strength, which increases exponentially as the strain rates increase. Scanning electron microscopy micrographs of the fractured specimen are employed to analyze the fracture characteristics. Graphical Abstract: (Figure presented.) © Iran Polymer and Petrochemical Institute 2024.