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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Figure 16.Stacked layers-CAD layers in the detailed ACP (Pre) model, arrangement of the material layers.

Finite element analysis (FEA) conducted under static loading conditions within an elastic-plastic simulation framework. Within the Ansys Composite Pre-Post (ACP) software, we conducted a comparative assessment of stresses within the individual layers. It's worth emphasizing that the Finite Element Analysis (FEA) for these structures employed a multilinear isotropic hardening model for this purpose. The equivalent stress and strain acquired from the static models in ACP(Pre) and structural analysis system and for more detailed analysis, principal stresses (S1) were calculated in ACP(Post) simulation to achieve stresses for critical layers. After analyzing all layers of the 3D printed PLA model, it became evident that the outer layers consistently exhibited higher stress levels in comparison to the inner layers displayed in Table 1. In reality, this phenomenon can be primarily attributed to the inherent imperfections in the bonding between adjacent layers, a characteristic feature of the 3D printing process. These imperfections result in the concentration of stress at the outermost layers, as they bear the primary load and transmit it to the inner layers. Additionally, the outer layers are in direct contact with the external environment and loading conditions, making them more susceptible to experiencing elevated stress levels. During the 3D printing process, each layer is sequentially deposited on top of the previous one, and the quality of bonding between these layers is influenced by factors such as cooling rates, material flow, and temperature variations. Consequently, the outermost layers are more likely to endure significant stress due to their position in the material stack and their crucial role in the transfer of loads to the inner layers. It is noteworthy that, despite these variations, stresses across all layers remained closely aligned, a phenomenon attributed to the large number of layers within a relatively small thickness, effectively distributing stress throughout the material. Therefore, we chose to consider layer number 35 for a comparative analysis as a representative example.

Table 1.Calculated stresses in critical layers for notched specimens in ACP(Post) analysis

Number of layers

Stress in specimen with one hole [MPa]

Number of layers

Stress in specimen with two holes [MPa]

5 8

25.53

4 7

25

24.1 23.8

23.7

28 35 45 58 64 68

10 20 28 35 54 68

22.39

23.33

22

24

21.9 21.4 22.3

24.5 24.9 25.2

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