PSI - Issue 47

Liviu Marsavina et al. / Procedia Structural Integrity 47 (2023) 744–748 Author name / Structural Integrity Procedia 00 (2019) 000–000

745

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mechanical properties obtained using FDM, particularly the toughness, strength, and stiffness. However, they refer at toughness as the area below the stress – strain curve. Arbeiter et al. (2018), Ahmad and Susmel (2018, 2019), Valean et al. (2020), Marsavina et al. (2022) experimentally determined the fracture toughness of PLA materials. Investigating the influence of manufacturing parameters on mode I fracture toughness (K IC ) they obtained values between 3.5 to 7 MPa m 0.5 for PLA, Arbeiter et al. (2018). Ahmad and Susmel (2018, 2019) found a value of 3.7 MPa m 0.5 for mode I fracture toughness. They also successfully employed the Theory of Critical Distance (TCD) for assessing the fracture of notched PLA specimens. The TCD method is claimed to be applied to non-homogeneous materials, like 3D printed ones, Marsavina et. al (2023). Marsavina et al. (2022) provided values for the mode II fracture toughness of PLA in the range 2.4 to 3.6 MPa m 0.5 , determined using Single Edge Notch Bend specimens loaded in asymmetric four point bending. Bahrami et al. (2020) tested Semi-Circular Bend specimens in order to investigate the effect of in-plane layer orientation on mixed-mode I-II fracture behavior of 3D-printed poly-carbonate with different mode mixities and printing orientations. The mode I fracture toughness in stronger and weaker direction was found 2.44 MPa m 0.5 , respectively 1.91 MPa m 0.5 . They employed the maximum tangential stress (MTS) and the generalized MTS (GMTS) criteria to assess the fracture of 3D printed specimens. Ayatollahi et al. (2020) investigated the effect of in-plane raster orientation on the tensile and fracture strengths of poly-lactic acid (PLA) samples made by fused deposition modeling technique. They used dog-bone and the semi-circular bending (SCB) specimens to investigate the tensile and mode I fracture behavior of the 3D-printed PLA specimens. Khosravani and Zolfagharian (2020) experimentally investigated the fracture of U-notched 3D-printed parts under mode I and mixed mode I /II. The 3D-printed made of polycarbonate and Nylon filaments using FDM weakened with a central bean-shaped slit with two U-shaped ends were considered. They employed the Equivalent Material Concept and J – Integral to predict the critical load. The present study presents some preliminary results on the notch effect on PETG specimens obtained using FDM.

Nomenclature a

crack/notch length

K IC P max

mode I fracture toughness

fracture load

R

radius of SCB specimens thickness of specimens

t

W

energy

notch radius



2. Materials and additive manufacturing parameters Polyethylene terephthalate glycol (PETG) polymer was used for specimens fabrication. The Semi-Circular Bend specimens (SCB) were considered with sharp notch  =0  and round notches (  =0.8 and 2.2 mm) were adopted, Fig. 1, with four different sizes R=10, 20, 30 and 40 mm and a thickness of 6 mm.



R



R

R

a

a

a

(a) V - notch;

(b) Round notch  = 0.8 mm;

(c); Round notch  = 2.2 mm;

Fig. 1. Semi-Circular Bend specimens.