Abstract
Paper explores the influence of the infill density (%), as a process parameter in additive manufacturing (3D printing), upon the mechanical (tensile, impact) and thermo-physical properties of PLA samples. The results indicated degradation of both tensile strengths and moduli with decrease of samples’ relative density from 100% to 25% with 49.9% and 42.0%, respectively. Similar behaviour holds on impact strength values that degrades with 56.0% for the samples printed using a 25% infill density. The Young’s modulus variation with relative density values was approximated using a 3rd order polynomial function, in accordance with the expression for closed-cell thick edge rhombus cellular structures. All PLA samples revealed small difference on their coefficients of linear thermal expansion, irrespective of their infill densities, with a decrease of 6.34% in the lowest relative density value specimens, indicating enhanced stability within selected temperature range. Glass transition temperatures were approximately located at 65°C whereas cold-crystallization around 80°C, thus unaffected by selected process parameter.
Keywords: polylactic acid (PLA); additive manufacturing; mechanical properties; thermal stability