PSI - Issue 34

Carla M. Ferreira et al. / Procedia Structural Integrity 34 (2021) 205–210 Carla M. Ferreira et al./ Structural Integrity Procedia 00 (2019) 000 – 000

206

2

The final mechanical properties of FFF parts are strongly influenced by the large amount of printing parameters and combinations between them, making it difficult to predict and to increase build parts ’ strength and stiffness. Several authors have dealt with the influence of printing paraments such as air gap, build orientation, infill pattern, infill density, layer heigh, raster orientation, raster width and number of printed contours, to optimize comp onents’ mechanical properties under static loading conditions. Tensile properties of FFF components are already well documented in the literature (Cantrell et al., 2017; Dey et al., 2019; Leite et al., 2018; Vicente et al., 2020) but only few authors have studied FFF components under torsional loadings (Balderrama-armendariz et al., 2018; Torres et al., 2016). Apart from the mechanical properties that affect component’s behavior and performance , it is also important to consider the loading conditions that affect the durability, long-term reliability, and fatigue life of the materials. Fatigue properties are important to understand the ability of a material to withstand cyclic loadings during usage. Some authors have already studied the properties of FDM parts under tensile (Lee et al., 2013; Ziemian et al., 2015) and bending (Domingo-Espin et al., 2018) cyclic loadings, but few have studied the impact of torsional cyclic loadings, leaving a gap in the literature to be fulfilled. Therefore, the present study aims to broaden the understanding of torsional monotonic and fatigue properties of 3D printed polymeric materials.

Nomenclature ABS

Acrylonitrile-butadiene-styrene Additive manufacturing

AM FFF

Fused filament fabrication ASTM American Society for Testing and Materials ISO International Organization of Standardization HCF High cycle fatigue

2. Methodology The present work aims to study the performance of solid cylinder specimens produced by 3D printing under static and cyclic torsional loads. To accomplish this, ABS from Ultimaker® in the form of a green filament was used and specimens were printed using Ultimaker3 and its own slicing program, Cura 4.9. 2.1. Specimen geometry Since there is no specific standard concerning AM of polymeric cylindrical components under monotonic torsion and cyclic loadings, the guidelines from the ASTM standard E143-13 and ISO-18338-2015 were taken into consideration to design the test method and specimen shown in Fig. 1. Specimens were printed in the up-right, Z, direction since support structures would be required if specimens were printed in the X or Y orientations.

Fig. 1. ABS solid cylinder specimen geometry (mm).

2.2. Monotonic torsion tests Instron® 8874 biaxial servohydraulic testing system was selected to perform both monotonic and fatigue tests. The double-acting servohydraulic actuator can produce a maximum torque of 25 N.m. Monotonic torsion tests were