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 Additive Manufacturing of Three-Phase Syntactic Foams Containing Glass Microballoons and Air Pores(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2019) Singh, A.K.; Deptula, A.J.; Anawal, R.; Doddamani, M.; Gupta, N.High-density polyethylene and its syntactic foams reinforced with 20 vol.% and 40 vol.% glass microballoons were 3D printed using the fused filament fabrication method and studied for their compressive response. The three-phase microstructure of syntactic foams fabricated in this work also contained about 10 vol.% matrix porosity for obtaining light weight for buoyancy applications. Filaments for 3D printing were developed using a single screw filament extruder and printed on a commercial 3D printer using settings optimized in this work. Three-dimensional printed blanks were machined to obtain specimens that were tested at 10 ?4 s ?1 , 10 ?3 s ?1 , 10 ?2 s ?1 and 1 s ?1 strain rates. The compression results were compared with those of compression-molded (CM) specimens of the same materials. It was observed that the syntactic foam had a three-phase microstructure: matrix, microballoons and air voids. The air voids made the resulting foam lighter than the CM specimen. The moduli of the 3D-printed specimen were higher than those of the CM specimens at all strain rates. Yield strength was observed to be higher for CM samples than 3D-printed ones. © 2019, The Minerals, Metals & Materials Society.