Impact of Aging Effect and Heat Treatment on the Tensile Properties of PLA (Poly Lactic Acid) Printed Parts

Abstract

Rapid innovations in 3D printing technology have allowed highly complex parts to be manufactured quickly and easily, particularly for prototyping purposes. Fused Deposition Modeling of thermoplastic materials is one of the most commonly used techniques in three-dimensional (3D) printing. The major aim of Fused Deposition Modeling (FDM) is to design and manufacture usable parts for fields such as engineering and medicine. Therefore, it is essential to investigate the mechanical properties of such FDM processed structures. One of the most commonly used materials currently on the market is Polylactic Acid (PLA). The main purpose of this paper is to investigate the effects of aging and heat treatment on the tensile properties of PLA printed test specimens. The tensile properties of parts manufactured by the 3D printer are influenced by various parameters such as extrusion temperature, infill density, building direction, layer height, etc. A total of 96 specimens were built by altering building orientation and layer height to estimate and compare the tensile properties of the printed parts. To investigate the aging effect, 30 of 96 specimens were printed 6 months before the tensile experiment. Half of both aged and new specimens were cured in an oven at 57.5 [˚C] for 3 hours while the other half endured no heat treatment. After the performed measurement, it can be concluded that heat treatment generally improves structural strength of the printed parts, while aging decreases it. However, these effects are highly dependent on the layer thickness and printing quality. The tensile test is conducted according to the ASTM D638 standard. The fractured samples were further characterized using an electron microscope.