PSI - Issue 41

Mohammad Reza Khosravani et al. / Procedia Structural Integrity 41 (2022) 664–669 Mohammad Reza Khosravani et al. / Procedia Structural Integrity 00 (2022) 000–000

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to traditional processes. A review of the literature reveals that 3D printing has been used in a wide range of applica tions including electronics (Yu et al., 2017), automotive (Khosravani and Reinicke, 2021a), aerospace (Reddy et al., 2018), and medicine (Pugliese et al., 2021). Regarding to increasing applications of 3D printing technology, various engineering aspects such as environmental e ff ects, fatigue strength, and structural integrity have been investigated in this field. Although 3D printing was introduced for fabrication of prototypes and small-scale production, currently it is a man ufacturing process which has been utilized for fabrication of functional end-use products. Therefore, the mechanical strength and structural integrity of the 3D-printed components have become of significant importance. In this context, fatigue and fracture behavior of 3D-printed parts have been investigated in several research works (Zolfagharian et al., 2020; Ekoi et al., 2021; Karpenko et al., 2022; Li et al., 2022). For instance, in (Polyzos et al., 2021) delamination in 3D-printed fiber reinforced parts has been studied. More in deep, nylon 3D-printed specimens reinforced with carbon fibers are fabricated and subjected to the delamination test. The researchers used analytical methods and numerical models to measure the fracture toughness of the examined 3D-printed parts. Based on the obtained results, it is con cluded that polynomial chaos expansion technique is accurate and practical means of explaining the behavior of the 3D-printed composites with continuous fibers. At the same time, e ff ect of graphene addition on the fracture behavior of 3D-printed PLA specimens was investigated in (Martinez et al., 2021). To this aim, single edge notched bend spec imens were printed using PLA material based on the fused deposition modeling (FDM) technique. A series of test was performed under static loading conditions and tensile properties of examined parts were obtained. The experimental findings showed that the graphene addition leads to an improvement of the ultimate tensile strength and a reduction in the strain under maximum load. In detail, the e ff ects of graphene on the ultimate tensile strength depends on the raster orientation: it is barely modified in 0 ◦ / 90 ◦ orientation, slightly increased in 30 ◦ / -60 ◦ and significantly improved in 45 ◦ / -45 ◦ in the examined specimens. A review of the literature reveals that FDM technique has been used in several academic and research projects (Parada et al., 2019; Duranovic et al., 2022; Li et al., 2022). For example, in (Verma et al., 2021) it has been docu mented that the FDM is best technique for 3D printing of PEEK with biomedical applications. A 3D printer based on the FDM technique consists of a stock feed material that extrudes in a semi-solid state via a temperature-controlled nozzle. The FDM 3D-printed parts can be used as di ff erent structural elements. In some cases, the assembly of struc tures made by 3D-printed parts cannot avoid the presence of holes or cut outs that can leads to stress concentrations and reducing the strength. Therefore, structural integrity of these components must be investigated. In fact, due to its importance, predicting the mechanical strength and fracture analysis of plates with open-holes has have been inves tigated in previous research works (Ma et al., 2021; Wu et al., 2021; Zhang et al., 2022). Since matrix fracture, fiber fracture and delamination can be occurred in the composites, the failure process is complicated. In the study (Ma et al., 2021), a conforming augmented finite element method is extended to predict the failure in an open-hole composite laminates. The researchers conducted tensile tests on the composite laminates and utilized digital image correlation technique for analysis of crack propagation. Based on the experiments, elastic modulus of 1528.7 MPa is reported. According to DIC, the cracks’ propagation is always along with a sudden load drop, and the cracks’ initiating prior to the load sudden drop slightly. Considering the results, it can be concluded that cracks occur before the structure’s destruction, and the conforming augmented finite element method is able to predict composite laminates’ failure per fectly. Later, tensile failure of 3D woven composite with an open hole is investigated in (Zhang et al., 2022). In this context, specimens are prepared with low porosity and customized continuous carbon fibers reinforcement. Experi mental finding show that the strength of the sample with fiber paths along maximum stress trajectories was improved by 166% compared with the traditional unidirectional fiber placement with drilling. The present study aims to investigate the mechanical strength of 3D-printed open hole plates. To this aim, PLA material is used to fabricate specimens and a series of tensile tests are conducted under static loading conditions. Since ratio of the specimen width to the hole diameter has e ff ect on the strength of the part, here specimens with two di ff erent hole diameters are prepared and examined. Based on the tests, ultimate tensile strength of the 3D printed plates are determined. Parallel to the experimental practices, numerical simulations are performed and a good agreement between experimental findings and and simulation results is observed. This work is structured as follows: in Section 2 an overview of FDM process is presented. Section 3 explains design and fabrication of specimens and details of experimental tests. Section 4 provides necessary information about numerical simulation of conducted tests. Section 5 draws the conclusion of this paper.