Using internal micro-scale architectures from additive manufacturing to increase material efficiency

Abstract

Several strategies have been posed to mitigate environmental burdens from plastics manufacturing. Two growing areas of exploration have been the use of bio-derived plastics and the use of material efficiency principles to reduce overall plastics demand. Bio-derived plastics are typically considered to be more environmentally sustainable than their petroleum-based counterparts. Additionally, advances in manufacturing technology have broadened the potential to use materials in an efficient manner by controlling internal structures, thus reducing dependency on solid components. The goal of this work was to provide an initial perspective into how internal microstructures in bio-derived plastics can broaden their range of mechanical and thermal properties, while reducing resource consumption. To determine the ability to influence material efficiency in this manner, poly(lactic) acid specimens were manufactured with 25%, 50%, 75%, and 100% infill percentages, using additive manufacturing to incorporate a microscale internal octagram spiral geometry. Tensile, flexural, and thermal conductivity properties of these plastics were compared to properties attained through conventional injection molding of poly(lactic) acid. Results showed the incorporation of an internal microstructure in thermoplastics caused reductions in both tensile and flexural moduli and strength, with typical losses of 30% in tensile properties and 20% in flexural properties. Yet improvements were noted to toughness and elongation properties, as well as lower thermal conductivity with the incorporation of a complex internal structure. Additionally, examination of specific properties of the poly(lactic) acid components and use of Ashby material indices showed the use of additive manufacturing could notably improve material efficiency, particularly apparent for the 25% infilled specimens. This work revealed potential improvements to energy dissipation and ductility through unique deformation mechanisms attained by additive manufacturing processing. • Control of internal geometry can increase material efficiency in member design. • Additive manufacturing may alter ductility and deformation mechanisms in components. • Voids resulting from changes to internal geometry can affect thermal conductivity. • Selection of processing techniques can drastically influence environmental impacts.