Faculty Publications
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Item Synthesis and application of sustainable vegetable oil-based polymers in 3D printing(Royal Society of Chemistry, 2024) Saraswat, R.; Shagun, N.; Dhir, A.; Balan, A.A.S.; Powar, S.; Doddamani, M.In the past ten years, there has been significant growth in the global 3D printing market, particularly in the development of natural and bio-based polymers. However, a major challenge is the limited availability of sustainable 3D printable resins capable of matching the performance of synthetic materials. This underscores the urgent need for the development of innovative and environmentally friendly resin materials. Herein, we introduce bio-based polymers, highlighting their recent advancements and offering a comprehensive overview of their diverse applications across various fields, including 3D printing. An area that has received less attention in this domain is polymers derived from vegetable oil (VO) or plant-based oil. Specifically, we thoroughly investigate the acrylation of epoxidized VOs and the subsequent formation of resins from these acrylates, which are essential materials for digital light processing (DLP), stereolithography (SLA), and extrusion-based 3D printing. The chemical modification of VOs, such as epoxidation and acrylation, is extensively explored, together with their respective types and applications. Furthermore, we delve deeply into the suitability of acrylate resins for 3D printing purposes. In conclusion, this review offers insights into the potential applications of 3D printed products utilizing materials derived from VOs. © 2024 The Author(s).Item Eco-friendly lightweight filament synthesis and mechanical characterization of additively manufactured closed cell foams(Elsevier Ltd, 2019) Patil, B.; Bharath Kumar, B.R.; Bontha, S.; Balla, V.K.; Powar, S.; Hemanth Kumar, V.H.; Suresha, S.N.; Doddamani, M.Environmentally pollutant fly ash cenospheres (hollow microballoons) are utilized with most widely consumed, relatively expensive high density polyethylene (HDPE) for developing lightweight eco-friendly filament for 3D printing of closed cell foams. Cenospheres (20, 40 and 60 by volume %) are blended with HDPE and subsequently extruded in filament to be used for 3D printing. Cenosphere/HDPE blends are studied for melt flow index (MFI) and rheological properties. MFI decreases with cenospheres addition. Complex viscosity, storage and loss modulus increase with filler loading. DSC results on the filament and printed samples reveal increasing crystallization temperature and decreasing crystallinity % with no appreciable change in peak melting temperature. Cooling rate variations exhibit crystallinity differences between the filament and the prints. CTE decreases with increasing cenosphere content resulting in lower thermal stresses and under diffusion of raster leading to non-warped prints. Micrography on freeze fractured filament and prints show cenospheres uniform distribution in HDPE. Intact cenospheres lower the foam density making it lightweight. Tensile tests are carried out on filaments and printed samples while flexural properties are investigated for 3D prints. Cenospheres addition resulted in improved tensile modulus and decreased filament strength. Tensile and flexural modulus of printed foams increases with filler content. Results are also compared with injection molded samples. Printed foams registered comparable tensile strength. Specific tensile modulus is noted to be increased with cenospheres loading implying weight saving potential of 3D printed foams. Property map reveals printed foams advantage over other fillers and HDPE composites synthesized through injection and compression molding. © 2019 Elsevier LtdItem Drilling parameter optimization of cenosphere/HDPE syntactic foam using CO2 laser(Elsevier Ltd, 2022) Singh, S.; Yaragatti, N.; Doddamani, M.; Powar, S.; Zafar, S.High-density polyethylene is a high-strength, and low-weight material system. Besides numerous applications in a variety of fields and products, its machining for generation of holes is rather difficult with traditional methods such as drilling as the process is not very conducive for composites due to associated damage. Hence, a non-contact material removal process such as laser machining provides an appealing, cost-effective, accurate, and fast alternative. For this study, the effect of the laser process controls key parameters such as laser power and laser speed on the cut surface integrity defined by surface roughness, kerf taper angle, and heat-affected zone of neat HDPE and HDPE with 60 wt% cenosphere was investigated and optimized using response surface methodology. Also, the machining operation was visualized using a Photron FASTCAM SA 1.1 high-speed camera to observe the effects of the high-intensity laser beam on specimens and to investigate the mechanism of laser machining. The optimum values for a defect-free cut surface (minimum surface roughness and low kerf taper angle) in neat HDPE comes out to be as laser power of 97.5 W and laser speed of 5 mm/s, with corresponding surface roughness and kerf taper angle of 54.304 μm and 0.152 degrees respectively and the optimum input values for HDPE with 60 wt% cenosphere are 102.126 W laser power and 5 mm/s laser speed, with corresponding surface roughness and kerf taper angle of 26.574 μm and 0.253 degrees. This study finds importance for the industrial and medical application to creates small size holes for mechanical joints such as rivets, bolts, and screws in assembly as low surface roughness and kerf width are always preferred as quality parameters in creating holes for industrial applications. © 2022Item Mechanical response of additively manufactured foam: A machine learning approach(Elsevier B.V., 2022) Neelam, R.; Kulkarni, S.A.; Bharath, H.S.; Powar, S.; Doddamani, M.This paper uses ensemble and automated machine learning algorithms to predict the mechanical properties (tensile and flexural strength) of a three-dimensionally printed (3DP) foamed structure. The closed cell foams were made from the most commonly used thermoplastic, High-Density Polyethylene (HDPE). The hollow glass microspheres are infused in HDPE at varying volume %. The available data on these foams' mechanical properties are used by the chosen machine learning (ML) algorithms to propose the best suited algorithm for such a three-phased microstructure as these closed cell foams exhibit. Finally, the strength predictions from the models were validated using experimental data. The models were trained with nozzle temperature, bed temperature, and force values as input parameters. The output parameters predicted were the tensile and flexural strength. LightGBM outperforms all other models in terms of performance among ensemble-based models, while H2OAutoML outperforms all other models. All the ML algorithms produced models with greater than 95% accuracy. Finally, memory and time consumption for each model are presented. © 2022 The AuthorsItem Buckling and free vibrations behaviour through differential quadrature method for foamed composites(Elsevier B.V., 2023) Duryodhana, D.; Waddar, S.; Bonthu, D.; Jeyaraj, P.; Powar, S.; Doddamani, M.The current work focuses on predicting the buckling and free vibration frequencies (fn) of cenosphere reinforced epoxy based syntactic foam beam under varying loads. Critical buckling loads (Ncr) and fn are predicted using the differential quadrature method (DQM). Ncr and fn have been calculated for beams of varying cenosphere volume fractions subjected to axial load under clamped-clamped (CC), clamped-simply (CS), simply-simply (SS), and clamped-free (CF) boundary conditions (BC′s). Upon increasing the cenosphere volume fraction, Ncr and fn of syntactic foam composites increases. These numerical outcomes are compared with the theoretical values evaluated through the Euler-Bernoulli hypothesis and further compared with experimental outcomes. Results are observed to be in precise agreement. The results of the DQM numerical analysis are given out for the different BC′s, aspect ratios, cenosphere volume fractions, and varying loads. It is perceived that depending on the BC′s, the type of axial varying loads and aspect ratios has a substantial effect on the Ncr and fn behaviour of the syntactic foam beams. A comparative study of the obtained results showed that the beam subjected to parabolic load under CC boundary conditions exhibited a higher buckling load. © 2023 The AuthorsItem Buckling behavior of non-uniformly heated 3D printed plain and functionally graded nanocomposites(John Wiley and Sons Inc, 2023) Kumar, S.; Ramesh, M.R.; Jeyaraj, J.; Powar, S.; Doddamani, M.The functionalized multi-walled carbon nanotubes (MWCNTs) (0.5–5 wt.%) are compounded with high density polyethylene (HDPE), and, subsequently, used for extruding nanocomposite filaments to fabricate nanocomposites (NCs) and functionally graded nanocomposites (FGNCs) through 3D printing. The 3D printed NCs are investigated for coefficient of thermal expansion (CTE), and buckling under different non-uniform temperature distributions (case-1: left edge heating, case-2: centre heating, and case-3: left and right edge heating). A significant reduction in CTE is observed with MWCNT addition and gradation. The highest reduction in CTE is observed for H5 (5 wt.% of MWCNT in HDPE) NC and H1 ⟶ H3 ⟶ H5 (FGNC-2) among the NCs and the FGNCs. It is noted that Tcr (critical buckling temperature) is highest for case-3 and lowest for case-2. The highest deflection is noticed in case-2, while no significant difference is observed in case-1 and case-3 heating conditions. It is also observed that Tcr increases with gradation and MWCNTs addition. The H5 NC and FGNC-2 exhibited the highest Tcr among the NCs and FGNCs, respectively. The maximum deflection is noticed for HDPE, whereas the minimum deflection is noticed for FGNC-2 and H-5 NC among the tested samples. The results also revealed that Tcr is very sensitive to type of heating. © 2023 Society of Plastics Engineers.Item 3D printed functionally graded foams response under transverse load(Elsevier B.V., 2023) Bonthu, D.; Mahesh, V.; Powar, S.; Doddamani, M.The applications of 3D printing are rapidly increasing in aerospace and naval applications. Nonetheless, 3D printing (3DP) of graded foams exhibiting property variation along the thickness direction is yet to be explored. In the current work, the different volume fractions of hollow glass micro balloon (GMB) reinforced high-density polyethylene (HDPE) composite based graded foams are 3D printed using the fused deposition modelling (FDM) technique. The bonding between successive layers and porosity distribution of these graded configurations are studied using micro-CT scan. Further, the 3D Printed functionally graded foams (FGFs) are tested for flexural response, and results are compared with numerical values. The micro-CT results showed delamination absence between the layers. In neat HDPE layers, porosity is not evident, while minor porosity creeps in the layers having the highest GMB content. Experimental results of the flexural test showed that the graded sandwiches exhibited better strength than the graded core alone. Compared to neat HDPE, the modulus of FGF-2 (H20–H40–H60) increased by 33.83%, implying better mechanical stiffness. Among all the FGFs, FGF-2 exhibited a better specific modulus. A comparative study of experimental and numerical results showed a slight deviation due to neglecting the induced porosity. © 2023 The Authors