PSI - Issue 53

Reza Ahmadi et al. / Procedia Structural Integrity 53 (2024) 97–111 Author name / Structural Integrity Procedia 00 (2019) 000–000

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It's essential to acknowledge that any differences between the numerical and experimental results can be attributed to a fundamental assumption inherent in finite element analysis. The simulation assumes perfect bonding between adjacent filaments in the 3D printed structure. In practice, achieving such ideal bonding can be challenging, and this assumption introduces certain limitations to the analysis. Furthermore, in the context of 3D printing, as we will demonstrate in fractography analysis, the presence of voids and defects is inevitable. This intrinsic nature of 3D printing can impact the material's structural integrity and mechanical behavior, and it's a crucial consideration in understanding the real-world performance of 3D printed components. 4.3. Fractography 3D printing, depending on the printing method and parameters used, can result in the formation of voids or air pockets within the printed material. These voids can act as stress concentration points and reduce the effective load carrying capacity of the material. They may also contribute to a more complex stress distribution around the holes and notches. The specific types and prevalence of defects on the fracture surface can vary depending on factors such as the 3D printing process, the quality of the material, and the nature of the loading conditions.

Porosity

Voids caused by poor layer adhesion.

Air voids

Figure 19.Surface fracture of un-notched specimen with detailed view

Figure 20.Surface fracture of notched specimen with one hole

Figure 21.Surface fracture of notched specimen with two holes

After static tensile tests the fracture surfaces have been evaluated through an optical microscope. All specimens displayed characteristics of both brittle and ductile fracture and it was shown that the material undergoes some plastic deformation before failing in a somewhat more ductile manner than pure brittle fractures. According to the following figures, in the vicinity of the holes, specimens experienced layer bonding defects, air voids and surface irregularities. According to the fracture surfaces, the presence of a high amount of internal porosity is a notable finding. The manufacturing defects in the cross-section of both notched and un-notched specimens is a common issue that can have a profound impact on the structural integrity and performance of 3D printed materials (Figure 20,21). These defects can originate from a multitude of sources during the 3D printing process, leading to irregularities, inhomogeneities, and structural inconsistencies within the material. These issues underscore the critical need for identifying, addressing, and mitigating manufacturing defects to enhance the quality and reliability of printed components.