PSI - Issue 31

Mohammad Reza Khosravani et al. / Procedia Structural Integrity 31 (2021) 105–110 Mohammad Reza Khosravani et al. / Procedia Structural Integrity 00 (2020) 000–000

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in fabrication of geometrically complex components. Indeed, the ability to create complex parts with high accuracy and economic benefits can be considered as the primary advantages of AM compared to conventional manufacturing processes. Considering advantages of 3D printing technology, additively manufactured components have been used in di ff erent applications such as aerospace (Joshi and Sheikh, 2015), electronics (Khosravani and Reinicke, 2020a), medicine (Nadagouda et al., 2020), automotive (Juechter et al., 2018), healthcare monitoring (Nasiri and Khosravani, 2020), food industry (Mantihal et al., 2020), and construction (Marchment and Sanjayan, 2020). Based on applica tions of 3D-printed parts, di ff erent engineering aspects have been investigated. For instance, previous research works studied ductility (Guan et al., 2019), load-carrying capacity (Khosravani and Zolfagharian, 2020), fatigue behavior (Ezeh and Susmel, 2018), environmental impacts (Khosravani and Reinicke, 2020b), and tensile properties (Wang et al., 2020) of 3D-printed components. Literature investigation confirmed that fracture study of di ff erent material was an interesting research topic over the years (IacovielloCocco, 2016; Papadopoulou et al., 2019; Baragetti et al., 2019; Monka et al., 2019; Vukelic et al., 2020; Cazin et al., 2020). In this context, fracture behavior of 3D-printed parts have been investigated in previous experimental studies and di ff erent methods have been used to evaluate fabrication and performance of 3D-printed parts (Decker et al., 2020; Khosravani and Reinicke, 2020c). In fact, with the aim to understand mechanical behavior and structural performance of 3D-printed parts various experimental practices were performed. Considering diverse applications of additively manufactured parts, further attempts are necessary. For practical applications, the printed components must withstand di ff erent amounts of mechanical and environmental stresses during their service life. In this respect, previous research works presented mechanical behavior of 3D-printed parts under di ff erent loading and environmental conditions (Xu et al., 2019; Papa et al., 2020). For instance, in (Khosravani et al., 2020) mechanical be havior of 3D-printed composite under di ff erent loads and environmental conditions has been described. More in deep, sandwich specimens with two types of core topologies were fabricated. The 3D-printed specimens were subjected to accelerated thermal ageing test and a series of tensile tests. Based on the documented results, the hexagonal lattice core has shown higher load carrying capabilities than triangular lattice in the examined polymers. In this study, influence of defect and thermal ageing on the mechanical behavior of 3D-printed parts have been presented. In this respect, specimens were printed using fused deposition modeling (FDM) process. In detail, test coupons were fabricated with di ff erent raster direction and a certain gap (as defect) intentionally placed into the specimens. In order to simulate natural environment during service life of the specimens, they experienced thermal ageing conditions. Later, both groups of unaged and aged specimens were subjected to a series of tensile tests and their mechanical behavior was compared. This work is structured as follows: in Section 2 an overview of AM is presented. Section 3 describes details of specimen preparation and experimental tests. Building on these experimental observations, the obtained results are presented. Finally, a short summary in Section 4 concludes the paper.

2. An overview of 3D printing technology

According to (ISO / ASTM 52900, 2015), 3D printing is ”process of joining materials to make objects from 3D model data, usually layer upon layer”. In 1984, Charles W. Hull invented stereolithography to create a tangible object (Bogue, 2013). 3D printing has changed industries and provided new opportunities in several fields. This manufactur ing process, stands out as a promising technology in fabrication of multi-functional and multi-material designs. A typical 3D printing workflow starts with the design using computer-aided design (CAD) software to prepare a CAD model. This CAD model must be sliced and then fed into the 3D printer to print the component. In Fig. 1 printing steps and trends in 3D printing processes are illustrated.

3D printing

M Slicing

3D design

M Final product

G CODE

M

STL file

G Code

Fig. 1. A typical workflow of 3D printing process.