Faculty Publications
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Item Sound absorption and transmission loss characteristics of 3D printed bio-degradable material with graded spherical perforations(Elsevier Ltd, 2022) Sailesh, R.; Yuvaraj, L.; Doddamani, M.; Mailan Chinnapandi, L.B.M.; Jeyaraj, J.The influence of spherical bubble perforations and their grading on acoustic characteristics of a 3D printed bio-degradable material is investigated. Samples with spherical bubble perforations of different sizes are distributed either uniformly or graded across the specimen thickness. A sample having typical cylindrical perforations is also analyzed for comparative analysis. Sound absorption (SA) and sound transmission loss (STL) characteristics are estimated by the impedance tube method. The results reveal that the SA of all functionally graded (FG) perforations is higher at low frequencies. The SA and bandwidth are higher for a specimen with uniform, lower diameter bubbles at higher frequencies. The STL of FG perforations is highest among the specimens, and the difference increases significantly with frequency. The numerical and experimental results match a high degree of accuracy. FG perforations exhibited superior performance for both SA and STL. The proposed graded spherical porosity can be effectively utilized in soundproofing applications across building and transportation sectors. © 2021 Elsevier LtdItem Quasi-static compressive behavior of bioactive glass reinforced high density polyethylene composites(Elsevier B.V., 2022) Jeyachandran, P.; Bontha, S.; Bodhak, S.; Krishna Balla, V.; Doddamani, M.Compressive behavior of additively manufactured bioactive glass (BAG) reinforced high density polyethylene (HDPE) composites under quasi static conditions (0.001, 0.01 and 0.1 s−1 strain rates) is investigated in this work. HDPE feedstock filaments with 5, 10 and 20 wt% of bioactive glass are extruded for fused filament fabrication (FFF) based 3D printing (3DP). Compressive properties are extracted from the stress–strain plots. Elastic modulus and yield strength of the samples increase with filler addition and strain rate. Energy absorption increases with increase in strain rate and BAG content. All the samples exhibit homogeneous ductile deformation with distinct barrelling effect without any visible cracks. Deformation and energy absorption behavior of the tested samples are investigated using micrography. © 2021 Elsevier B.V.Item Additive Manufacturing of Short Silk Fiber Reinforced PETG Composites(Elsevier Ltd, 2022) Kn, V.; Bonthu, D.; Doddamani, M.; Pati, F.The growing demand for customized medical devices like prostheses, orthoses, and implants is the prime motive for a surge in the investigation of 3D printable biocomposites. PETG (Polyethylene terephthalate glycol) based composites can be a good choice for biomedical applications. Specific characteristics of this material like biocompatibility, ease of formability, stable thermomechanical properties, and high chemical, and abrasion resistance make it suitable for biomedical applications. However, there are very few studies on the 3D printing of PETG-based composites. Development of a robust 3D printing protocol is required for any novel natural fiber reinforced PETG composites. This study presents natural fiber-reinforced PETG biocomposite filament preparation and 3D printing with the developed composite filaments. Silk was used as a filler material due to its high thermal stability and high tensile strength. Composite filaments with 2 wt%, 5 wt%, and 10 wt% silk were prepared using the extrusion process. Further, we developed a protocol for 3D printing with the developed composites to fabricate various 3D structure. Both filaments and printed specimens were characterized morphologically, structurally, and mechanically. The melt flow rate of the filaments decreased with an increase in fiber content which was a bottleneck for printing 10% silk-PETG composites. Micro-CT results validate an increase in void content in filaments on filler addition. The highest flexural modulus and flexural strength were exhibited by 2% silk-PETG printed parts and a 60% increase in compressive modulus compared to pure PETG. Tensile tests show that 2 wt% fiber addition significantly increased elastic modulus (2466.72 MPa) compared to pure PETG (902.81 MPa), whereas the surface roughness of printed composites increased with filler content. Finally, a lower limb prosthetic socket prototype was printed with a desktop 3D printer to demonstrate its potential for biomedical applications. © 2022 Elsevier LtdItem 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 Recycling potential of MWCNTs/HDPE nanocomposite filament: 3D printing and mechanical characterization(Springer, 2023) Kumar, S.; Ramesh, M.R.; Doddamani, M.Fused filament fabrication (FFF) based additive manufacturing (AM) process is a widely used and emerging manufacturing process for polymer-based products. The recycled filaments are realized through wastage generated while extruding the constant diameter feedstock filament, which is otherwise dumped in landfills or incinerated, releasing hazardous and toxic gases that influence the ecological environment. The wastage of these filaments can be eliminated by recycling and reusing them, addressing materials circular economy effectively, presented in this paper. The functionalized MWCNT reinforced HDPE (high-density polyethylene) nanocomposite (NC) is realized through a brabender, which is further used for filament extrusion. The waste/unrecycled (W/UR) and the recycled filaments are checked for quality. The density of the recycled filaments increases compared to the W/UR filament in each extrusion pass. The crystallinity and tensile properties of the recycled filaments increase compared to the W/UR filament with each additional extrusion cycle. Further, these filaments are used for 3D printing, and investigated for density, XRD and tensile tests. It is observed that the density, crystallinity and tensile properties of the recycled prints increase compared to the W/UR print. The tensile strength and modulus of 1 × , 2 × and 3 × prints are 63.82, 67.11 and 67.76%, and 45.63, 55.34 and 97.81% respectively, higher than those of the W/UR print. The highest tensile strength and modulus are observed for 3 × print which is 67.76 and 97.81% respectively, higher than those of the W/UR print. 3D prints exhibited enhanced performance as compared to their respective filaments. Finally, the present tensile results are mapped on a property chart, and compared with the available HDPE composites. © 2023, Springer Nature Japan KK, part of Springer Nature.Item 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 Dynamic response of 3D printed functionally graded sandwich foams(Emerald Publishing, 2023) Bonthu, D.; Bharath, B.; Bekinal, S.I.; Jeyaraj, J.; Doddamani, M.Purpose: The purpose of this study was to introduce three-dimensional printing (3DP) of functionally graded sandwich foams (FGSFs). This work was continued by predicting the mechanical buckling and free vibration behavior of 3DP FGSFs using experimental and numerical analyses. Design/methodology/approach: Initially, hollow glass microballoon-reinforced high-density polyethylene-based polymer composite foams were developed, and these materials were extruded into their respective filaments. These filaments are used as feedstock materials in fused filament fabrication based 3DP for the development of FGSFs. Scanning electron microscopy analysis was performed on the freeze-dried samples to observe filler sustainability. Furthermore, the density, critical buckling load (Pcr), natural frequency (fn) and damping factor of FGSFs were evaluated. The critical buckling load (Pcr) of the FGSFs was estimated using the double-tangent method and modified Budiansky criteria. Findings: The density of FGSFs decreased with increasing filler percentage. The mechanical buckling load increased with the filler percentage. The natural frequency corresponding to the first mode of the FGSFs exhibited a decreasing trend with an increasing load in the pre-buckling regime and an increase in post-buckled zone, whereas the damping factor exhibited the opposite trend. Originality/value: The current research work is valuable for the area of 3D printing by developing the functionally graded foam based sandwich beams. Furthermore, it intended to present the buckling behavior of 3D printed FGSFs, variation of frequency and damping factor corresponding to first three modes with increase in load. © 2023, Emerald Publishing Limited.Item Sound absorption and transmission loss of 3D printed wood fibre reinforced poly lactic acid with functionally graded perforations(Taylor and Francis Ltd., 2024) Sailesh, R.; Doddamani, M.; Mailan Chinnapandi, L.B.; Yuvaraj, L.; Pitchaimani, J.The effect of wood fibre reinforcement on acoustic properties of 3D printed poly lactic acid samples having varying cross-section perforation and functionally graded spherical perforations is presented. Acoustic characteristics like sound absorption as well as transmission loss are obtained using an impedance tube setup. Results revealed the benefits due to the addition of wood fibres in PLA improved samples’ sound transmission loss characteristics significantly. The sound absorption curve peaks shifted to low-frequency regions which are favourable to living beings. The material can be used in acoustic insulation for structural and transportation applications, especially where eco-friendliness and aesthetics are of major concern. © 2023 Informa UK Limited, trading as Taylor & Francis Group.Item 3D Printed Thick Micro-Perforated Panel with Graded Perforation for Practical Wall Sound Absorption Applications(Springer, 2024) Shafeer, M.; Pitchaimani, J.; Doddamani, M.In recent years, noise pollution has been recognized as a significant environmental issue, and using sustainable materials as sound-absorbing building materials have drawn considerable attention. The influence of graded perforations on the acoustic characteristics of a 3D printed bio-degradable thick micro-perforated panel (MPP) having graded perforation and made of Poly Lactic Acid is presented. Thicker panels are considered owing to the mechanical strength required for practical wall applications. A fused deposition modeling based 3D printer is used to fabricate the MPPs with graded cylindrical perforations and different patterning of perforations. The sound absorption coefficient is measured using the impedance tube technique and compared with theoretical results obtained using an equivalent electro-acoustic model. Results revealed that for normal incidence, the absorption coefficient is only dependent on the overall perforation ratio of the panel, irrespective of the perforation gradation and patterning of perforation. This gives the freedom to distribute the perforation aesthetically for interior wall application. This work also proposes the effective perforation ratio approach to predict the sound absorption coefficient (SAC) of MPPs with graded perforation. For multi-thickness MPPs and MPPs with linearly graded thickness, improved sound absorption characteristics were observed both in terms of bandwidth of absorption and peak value of SAC compared to the conventional constant thickness MPPs. © Australian Acoustical Society 2023.Item 3D printing of functionally graded nanocomposites: An investigation of microstructural, rheological, and mechanical behavior(John Wiley and Sons Inc, 2024) Kumar, S.; Rajath, S.; Shivakumar, N.D.; Ramesh, M.R.; Doddamani, M.Manufacturing functionally graded material through 3D printing is challenging owing to the deposition of different materials with different thermal properties in each layer, leading to a higher thermal gradient between deposited and depositing layers, resulting in improper bonding between them and, hence, reduced mechanical properties. This study focuses on 3D printing of functionalized multi-walled carbon nanotubes (MWCNTs)/high-density polyethylene (HDPE)-based lightweight functionally graded nanocomposites (FGNCs) and their investigation for microstructural, rheological, physical, and mechanical properties. Functionalized MWCNTs (0.5% → 5%) are initially compounded with widely utilized HDPE to develop nanocomposites (H0.5→H5 pellets) for extruding filaments for 3D printing. 3D-printed FGNC samples are investigated through scanning electron microscopy (SEM), rheology, density, tensile, and flexural tests. SEM and rheology confirm the homogeneous dispersion of the filler in HDPE and the processing parameters suitability in blending, extrusion, and 3D printing. Complex viscosity (η*), loss modulus (E″), and storage modulus (E′) of FGNCs increase, while the damping decreases with the MWCNTs rise in the graded layers. Density results revealed the highest weight saving potential (~12%) of FGNC-2 (H1–H3–H5), showing great weight saving potential. Tensile and flexural properties rise when the MWCNTs content rises in the graded layer. The FGNC-2 showed the highest tensile strength and moduli, 37.12% and 90.41% higher than HDPE. Flexural strength and moduli are also found to be the highest for FGNC-2, 28.57%, and 26.83% higher than HDPE. The highest specific moduli and strength are found for FGNC-2, 46.16% and 44.14% higher than HDPE, respectively. Experimental findings are found to be strongly in agreement with numerical findings. 3D-printed FGNC-2 demonstrated the best flexural and tensile characteristics with the lowest weight and hence can be used to make practical parts and structures that need variable stiffness. Highlights: FGNCs functionally graded n anocomposites are concurrently 3D printed. FGNC-2 exhibited the highest weight saving potential of 12%. FGNC-2 showed 90.41% and 37.12% enhanced tensile modulus and strength. FGNC-2 displayed 28.57% and 26.83% improved flexural strength and modulus. FGNCs exhibited better mechanical performance than the homogeneous NCs. © 2024 Society of Plastics Engineers.