On the visco-elasto-plastic response of additively manufactured polyamide-12 (PA-12) through selective laser sintering

Abstract

This work presents an in-depth study on the mechanical behavior of selective laser sintered (SLS) nylon (PA-12). The entire visco-elasto-plastic response is determined based on experimental data obtained through tensile, compression, shear and relaxation testing. In addition, ultrasonic non-destructive testing is proposed as an alternative to conventional testing for the derivation of the elastic properties of this material. An isotropic elastic behavior was observed, while a clear orthotropic and non-linear response was found for both the plastic curves and the relaxation behavior. Strength data suggests laser sintered PA-12 will fail in tension rather than in shear. The ultrasonic tests correspond well to conventional tensile data (at high rates), and represent a cost-effective alternative to extensive conventional tensile testing. The presented test data can potentially be used to derive a detailed material model suitable for modelling static, fatigue and impact applications using 3D printed PA-12

Material modelling and property mapping for structural FEA of thin-walled additively manufactured components

“…E ) scored highest and E 90 (i.e. E ⊥ ) lowest for each thickness, which is in line with the typical findings reported in the literature (Caulfield, McHugh, and Lohfeld 2007;Rüsenberg, Josupeit, and Schmid 2014;Ajoku et al 2016;Lammens et al 2017).…”

“…Therefore, a stereo digital image correlation (DIC) system computed the strain fields in the gauge length of the specimens, by frame-wise comparison of an un-deformed reference image with the displacement in a speckle pattern that was applied to the coupon surface using an airbrush. This yields the strain in principal 1 1 and traversal coupon axes 1 2 , which based on n = −1 2 /1 1 allows a contactless evaluation of the Poisson's ratios ν for the different build angles (Faes et al 2017;Lammens et al 2017). The DIC setup consisted of two monochrome 5 MP cameras (Grasshopper3, FLIR Integrated Imaging Solutions, Inc., Wilsonsville, OR, USA), recording at a frame rate of 2 Hz in conjunction with the post-processing software Vic-3D 9 (Correlated Solutions Inc., Irmo, SC, USA).…”

“…The aforementioned defect accumulations at the layer interfaces represent regions of poor bonding that in case of LS Pa12, result in a reduction (>11 %) of the mechanical material performance in ⊥-direction, including stiffness, strength and ductility, when compared to the in-plane loading case (Caulfield, McHugh, and Lohfeld 2007;Rüsenberg, Josupeit, and Schmid 2014;Ajoku et al 2016;Lammens et al 2017;Bain et al 2019). Moreover, it was revealed that samples fabricated in different directions parallel to the build platform exhibit similar properties (Cooke et al 2011), which is in synergy with the assumed existence of isotropic planes in the layered volume element.…”

Elastic Asymmetry of PLA Material in FDM-Printed Parts: Considerations Concerning Experimental Characterisation for Use in Numerical Simulations

“…In literature consulted concerning this test, the length of the specimens was usually twice its principal width or diameter. Exceptionally [32][33][34][35] long-length specimens were tested.…”

Stress-strain synchronization for high strain rate tests on brittle composites

“…All parts except the specimen were given the linear elastic properties of steel. The specimen was given a density and a linear elastic material model for which the values are given in [14] c: 65 % volume fraction yarn properties [18] d: Nested MESI finite element model [18] e: Values from quasi-static tensile tests f : Estimates…”