Annealing effect on mechanical properties of 3D printed composites

Fused filament fabrication (FFF) is the most popular additive manufacturing method, with which it is possible to obtain highly complex three-dimensional parts without wasting materials. In order to improve the mechanical properties of 3D printed materials, literature suggests the thermal annealing process. Therefore, this work aims to study the effect of thermal annealing on the bending properties of PETG and PETG reinforced with carbon and aramid fibres. For this purpose, the samples were printed using a B2X300 printer, with a hardened steel nozzle of 0.6 mm diameter, and the printing parameters were optimized for each material. Five specimens were tested according to ASTM D790-17 for each condition. Three temperatures (90ºC, 110ºC and 130ºC) and three annealing times (30 min, 240 min and 480 min) were used to study the benefits obtained with the thermal annealing. Finally, the samples were evaluated in terms of geometrical parameters, hardness, and flexural properties. Regardless of the materials studied, the best mechanical properties were obtained for the highest temperature and the longest exposure time, but due to the high geometric distortions, a temperature of 90 °C and an exposure of 30 minutes proved to be more effective.