PSI - Issue 37

Mohammad Reza Khosravani et al. / Procedia Structural Integrity 37 (2022) 97–104 Mohammad Reza Khosravani et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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2. An overview of fracture in 3D-printed polymer parts Considering applications of structural elements, several polymeric materials such as Acrylonitrile Butadiene Styrene (ABS), Polypropylene (PP), and Polyamide (PA) have been used for fabrication of the 3D-printed parts, which might be subjected to different loading conditions. Therefore, fracture study of different components has been an interesting topic over the years Moreira et al. (2012), Corigliano et al. (2016), Farahani et al. (2020). Based on the mechanical behavior of 3D-printed polymer parts, these components are rarely used as load-bearing structural elements. Recently, in Khosravani et al. (2020) fracture behavior of additively manufactured parts were reviewed. To this aim, both 3D-printed polymer parts and additively manufacture metallic components were considered to review the reported data were discussed and analyzed. As strength of components is reduced in the presence of a crack, utilizing fracture mechanics is beneficial in study the mechanical behavior cracked components. Although constitutive equations can be used for failure prediction in crack-free components, they are not useful when a component contains a crack. In a cracked specimen, a critical stress level can be determined which depends on different parameters such as applied stress, specimen size, crack size, and component geometry. Based on the practical applications of 3D-printed polymer parts, they can experience various loadings. Therefore, study the fracture resistance of 3D-printed polymer parts is a necessity. Despite numerous applications of 3D-printed parts, there is no specific standard for evaluation of mechanical fracture in 3D-printed structural components. In this context, researchers utilized international standards, which are already used for evaluation of plastic and metallic parts. In previous studies, specimens with different geometries and crack configurations were used in different experimental tests to determine fracture behavior of 3D-printed polymer parts. For instance, single-edge cracked specimens, compact tension specimens, and center cracked specimens were used in Swolfs and Pinho (2019), Isaac et al. (2020), Liu et al. (2020). Moreover, other experimental practices such as double cantilever beam (DCB) tests, three-point bending, tensile, and compression tests have been conducted. The cracked 3D-printed polymer specimens can be classified into two groups according to the crack fabrication techniques: (i) the crack is initiated after 3D printing process by pressing an ordinary razor blade into the notch, and (ii) the crack is manufactured in the 3D printing process. According to the previous experimental tests, a lower stress concentration has been documented for the specimens which produced by the first above-mentioned method. Table 1 presents the recent studies which deals with the fracture behavior of 3D-printed polymer parts.

Table 1. The recent studies of fracture behavior in 3D-printed polymer components.

References

Material

Test details

Results

Young et al. (2020)

ABS

DCB test

Effects of voids on the fracture toughness

Liu et al. (2020)

Plastic

3-point bending

Rubber-like deformation behavior

Banuelos et al. (2020) Djouda et al. (2020)

PP

Double-edge Single-edge

Role of raster orientation on structural integrity Load – strain curve for analysis of fracture Effect of spatial orientation on the fracture behavior Better properties in thin-layered printed parts Effect of raster angle on fracture behavior Influence of infill speed and density on fracture

ABS

Linul et al. (2020)

PA

4-point bending

Somireddy et al. (2020) Oviedo et al. (2020) Abeykoon et al. (2020)

ABS ABS PLA

Peeling test

3-point bending 3-point bending

In our previous research works, we have investigated fracture behavior of 3D-printed polymer parts. In detail, we have determined structural performance of 3D-printed composites under different loads and environmental conditions in Khosravani et al. (2020). More in deep, the sandwich specimens with two types of core topologies made similar 3D printing filaments were manufactured. A group of the specimens experienced thermal ageing conditions. Later, based on three-point bending tests, the failure behavior of the original and aged specimens was determined. At the same time, in Khosravani and Zolfagharian (2020) we have investigated fracture of 3D-printed cracked parts. Indeed, U notched 3D-printed parts were fabricated using polycarbonate and nylon filaments based on the FDM technique. A