Faculty Publications
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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 Mechanical behaviour of additively manufactured bioactive glass/high density polyethylene composites(Elsevier Ltd, 2020) Jeyachandran, P.; Bontha, S.; Bodhak, S.; Balla, V.K.; Kundu, B.; Doddamani, M.Bioactive glass (BAG) is a well-known biomaterial that can form a strong bond with hard and soft tissues and can also aid in bone regeneration. In this study, BAG is added to a polymer to induce bioactivity and to realize fused filament fabrication (FFF) based printing of polymer composites for potential orthopaedic implant applications. BAG (5, 10, and 20 wt%) is melt compounded with high density polyethylene (HDPE) and subsequently extruded into feedstock filament for FFF-printing. Tensile tests on developed filaments reveal that they are stiff enough to resist forces exerted during the printing process. Micrography of printed HDPE/BAG reveals perfect diffusion of raster interface indicating proper selection of printing parameters. Micrography of freeze fractured prints shows the homogeneous distribution and good dispersion of filler across the matrix. The tensile, flexural, and compressive modulus of FFF-printed HDPE/BAG parts increases with filler addition. BAG addition to the HDPE matrix enhances flexural and compressive strength. The tensile and flexural behaviour of FFF-prints is comparable to injection molded counterparts. Property maps exhibit the merits of present study over the existing literature pertaining to desired bone properties and polymer composites used in biomedical applications. It is envisioned that the development of HDPE/BAG composites for FFF-printing can lead to possible orthopaedic implants and scaffolds to mimic the bone properties in customised anatomical sites or injuries. © 2020 Elsevier Ltd