Isotropic Fused Filament Fabrication Additive Manufacturing
Additive manufacturing, also widely known as 3D printing, has attracted tremendous attention in almost every industry, from aerospace and defense, to automotive, electronics, dental and medical fields. It holds the promise to revolutionize the manufacturing. To date, however, parts printed from existing commercial materials for Fused Filament Fabrication (FFF) 3D printing, such as polylactic acid (PLA), acrylonitrile-butadiene-styrene (ABS), and NinjaFlex®, exhibit greater than 50% reductions in toughness when deformed perpendicular to the printed layers. The high anisotropy presented in the printed parts is the leading factor in the uncertain quality of final parts, and has obstructed FFF’s implementation in the additive manufacturing of functional engineering parts. In this work, two mechanisms are explored to enhance the interlayer adhesion, mitigate the anisotropy in printed parts and boost their reliability. One is the use of ionizing radiation to induce crosslinks between the printed layers after the part is printed. The γ rays radiation improves the interlayer adhesion by 60% in the case of parts printed from sensitized PLA. The other is applying dynamic furan-maleimide Diels-Alder chemistry in 3D printing materials, which has been validated as the second mechanism to introduce crosslinks into the printed part for anisotropy reduction. Parts printed from the DART polymers not only maintain greater than 95% toughness when deformed perpendicular to the printed layers, but exhibit smooth surface finish and reasonable bulk properties as well. Both mechanisms have demonstrated their encouraging capacity in isotropic FFF 3D printing, and expanded the range of polymer choices for additive manufacturing applications that have more advanced requirements in materials and printed parts.