Influência da temperatura ambiente e da orientação de construção no comportamento mecânico do PLA após impressão 3D por extrusão

Abstract

Understanding the thermomechanical behavior of the materials its essential for the researchers and the industry in general. From the manufacturing process to the use of the final product, temperature is a determining factor, since different temperature variations can cause different results in the physical, chemical and mechanical properties of the material chosen for a given application. The present work aimed to analyze the effect of temperature on the mechanical properties of PLA (polylactic acid) through tensile and three-point bending tests on specimens manufactured by 3D printing using FFF (Fused Filament Fabrication). The tests were carried out under three different temperatures: 5 °C, 25 °C and 45 °C. For this, an equipment capable of controlling the temperature during the tests was built, with operation similar to that of a commercial environmental chamber. The specimens were printed in three different orientations (flat, on-edge and upright) and distributed in 9 experimental groups of 5 units for each temperature and orientation, totaling 45 specimens for each test. The maximum stress, the modulus of elasticity and the yield limit were analyzed, and analysis of variance tests were used to verify if there was a significant difference between the groups. At 5 °C, the results showed that the decrease in temperature causes an increase in the stiffness of the PLA, creating a fragile behavior with higher stress values and lower strain values. In tests at 25 °C an intermediate ductile behavior was evidenced. At 45 °C, the results showed a drop in resistance and an increase in PLA plasticity, due to the proximity of the glass transition temperature. The specimens printed in the flat and on-edge orientations showed superior and similar mechanical performance. On the other hand, the specimens printed in the upright orientation showed the lowest values of the mechanical properties analyzed, due to the direction of deposition of the layers being perpendicular to the direction of the applied load, which caused the premature rupture of the specimens during the tests.