Processing and modeling of 3D-printed mill scale strengthened acrylonitrile butadiene styrene composites

Mill scale (MS) strengthened acrylonitrile-butadiene-styrene (ABS) composite filaments were fabricated as an optional low-cost and sustainable feedstock material with enhanced strength using fused filament fabrication (FFF) technology. In the present study, the effects of the FFF printing parameters on the mechanical properties of the printed ABS/1.0 vol% MS composites were evaluated. Test specimens of the composite were fabricated at printing temperatures of 240–280 °C, printing speeds of 10–90 mm s−1, and infill densities of 25–100%. Tensile tests and Izod impact tests were conducted for the specimens printed under different printing conditions to examine their mechanical characteristics. Afterwards, macro- and microstructural observations of the fractured specimens were carried out. The average maximum stress and modulus of the printed specimens increased when the printing temperature was raised to 270 °C while decreasing the printing speed, with numerous air gaps and pores found in the cross-sectional microstructures after failure at low infill density. High surface roughness of the printed composites was observed by a 3D laser scanner when printing at high temperatures and speeds due to insufficient cooling. The printed composite microstructures were examined by X-ray micro-computed tomography (μCT), and showed homogeneously dense particle dispersion in the entire printed part. Representative volume element (RVE)-based modeling was carried out using real particle geometries from the μCT. RVE simulations predicted high local stress distributions around mill scale particles and air gaps in the printed samples.