Influence of room temperature on the mechanical behavior of PLA for application in additive manufacturing

ABSTRACT

Polymers used for 3D printing with FFF technology are very sensitive to temperature variations, which occurs from its manufacturing process to its final usage. This is an important characteristic for the printing process, however it can represent a limiting factor for its use in environments with large temperature variations. Therefore, this paper aimed to analyze the mechanical behavior of PLA (polylactic acid) specimens manufactured by 3D printing using the FFF (Fused Filament Fabrication) technology and subjected to temperatures of 5°C, 25°C and 45°C. Tensile and three-point bending tests were performed on specimens manufactured in three different orientations (flat, on-edge and upright). An equipment, consisting of a thermal chamber and a temperature control system attached to the Universal Testing Machine, was used to control the temperature in the environment where the specimens were subjected to the mechanical tests. The specimens were distributed in experimental groups of 5 units each. All printing parameters were the same for all groups. PLA at 5°C showed a significant increase in the modulus of elasticity and yield strength, causing a more fragile behavior. At 25°C the mechanical behavior was similar to the literature. Lastly, at 45°C, a decrease in strength and a high increase in PLA plasticity were observed, due to the proximity of the glass transition temperature. The specimens printed in the flat and on-edge orientations presented similar mechanical performance, while the ones printed in the upright orientation presented the lowest values of the analyzed mechanical properties.

Keywords
FFF; 3D Printing; Thermomechanical Behavior; Environmental Chamber