Faculty Publications
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Item Additive Manufacturing of Syntactic Foams: Part 2: Specimen Printing and Mechanical Property Characterization(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Singh, A.K.; Saltonstall, B.; Patil, B.; Hoffmann, N.; Doddamani, M.; Gupta, N.High-density polyethylene (HDPE) and its fly ash cenosphere-filled syntactic foam filaments have been recently developed. These filaments are used for three-dimensional (3D) printing using a commercial printer. The developed syntactic foam filament (HDPE40) contains 40 wt.% cenospheres in the HDPE matrix. Printing parameters for HDPE and HDPE40 were optimized for use in widely available commercial printers, and specimens were three-dimensionally (3D) printed for tensile testing at strain rate of 10?3 s?1. Process optimization resulted in smooth operation of the 3D printer without nozzle clogging or cenosphere fracture during the printing process. Characterization results revealed that the tensile modulus values of 3D-printed HDPE and HDPE40 specimens were higher than those of injection-molded specimens, while the tensile strength was comparable, but the fracture strain and density were lower. © 2018, The Minerals, Metals & Materials Society.Item Additive Manufacturing of Syntactic Foams: Part 1: Development, Properties, and Recycling Potential of Filaments(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Singh, A.K.; Patil, B.; Hoffmann, N.; Saltonstall, B.; Doddamani, M.; Gupta, N.This work focuses on developing filaments of high-density polyethylene (HDPE) and their hollow particle-filled syntactic foams for commercial three-dimensional (3D) printers based on fused filament fabrication technology. Hollow fly-ash cenospheres were blended by 40 wt.% in a HDPE matrix to produce syntactic foam (HDPE40) filaments. Further, the recycling potential was studied by pelletizing the filaments again to extrude twice (2×) and three times (3×). The filaments were tensile tested at 10?4 s?1, 10?3 s?1, and 10?2 s?1 strain rates. HDPE40 filaments show an increasing trend in modulus and strength with the strain rate. Higher density and modulus were noticed for 2× filaments compared to 1× filaments because of the crushing of some cenospheres in the extrusion cycle. However, 2× and 3× filament densities are nearly the same, showing potential for recycling them. The filaments show better properties than the same materials processed by conventional injection molding. Micro-CT scans show a uniform dispersion of cenospheres in all filaments. © 2018, The Minerals, Metals & Materials Society.Item Compressive behavior of fly ash based 3D printed syntactic foam composite(Elsevier B.V., 2019) Patil, B.; Bharath Kumar, B.R.; Doddamani, M.Syntactic foams are widely used in damage tolerance and low-density applications. In present work compressive behavior of 3D printed three-phase syntactic foams under quasi-static strain rates (0.001, 0.01 and 0.1 s?1) are investigated. Extruded filaments of High density polyethylene (HDPE) with environmentally pollutant fly ash cenospheres (0, 20, 40 and 60 vol%) are used for 3D printing. Micrography reveal that syntactic foam filament and 3D printed samples are three phase systems comprising matrix, cenosphere and porosity. Matrix porosity of about 7% makes these foams lightweight and suitable for buoyant applications. The compressive properties are extracted from the stress-strain plots. It is observed that modulus and specific modulus increases with strain rate and cenosphere content. Specific compressive strength increases with strain rate and decrease with cenosphere content. © 2019 Elsevier B.V.