Issue 73

S. Mara ş et alii, Fracture and Structural Integrity, 73 (2025) 200-218; DOI: 10.3221/IGF-ESIS.73.14

C configurations, the highest natural frequencies are observed in configuration A, while the lowest are in configuration C. This is because as the core layer’s infill ratio increases, both the stiffness and the density of the structure increase. However, the increase in density has a more significant effect than the increase in stiffness, leading to a decrease in natural frequencies. Moreover, when the core material has the same infill ratio, the natural frequencies of the structures increase as the infill ratio of the surface materials increases. For example, among the A, E, and H configurations with a core infill ratio of 40%, the highest natural frequencies are observed in configuration H, while the lowest are in configuration A. This is due to the fact that as the infill ratio of the surface materials increases, the structural stiffness also increases. A stiffer surface layer enhances the flexural rigidity of the structure, thus increasing the natural frequencies. Furthermore, the graphs reveal that as the aspect ratio increases, the natural frequencies also increase due to the corresponding increase in structural stiffness.

a/b=1

100 150 200 250 300

A B G H I ω ₁ 80.35 78.79 78.05 79.19 80.63 78.51 85.76 88.03 86.52 ω ₂ 163.51 160.35 158.89 161.15 164.06 159.8 174.52 179.07 176.03 ω ₃ 163.51 160.35 158.89 161.15 164.06 159.8 174.52 179.07 176.03 ω ₄ 240.56 235.94 233.84 237.08 241.35 235.15 256.76 263.35 258.91 0 50 Configurations C D E F

Natural Frequency (Hz)

Figure 8: Variation of the natural frequencies of 3D-printed PA6 plates with fully clamped boundary conditions and an aspect ratio of a/b =1 for various configurations.

a/b=1.5

100 150 200 250 300 350 400

A B G H I ω ₁ 135.39 132.77 131.56 133.43 135.85 132.31 144.51 148.28 145.75 ω ₂ 208.68 204.66 202.83 205.66 209.36 203.97 222.73 228.45 224.6 ω ₃ 329.75 323.45 320.66 324.98 330.78 322.43 351.95 360.77 354.75 ω ₄ 331.9 325.55 322.73 327.1 332.95 324.51 354.25 363.17 357.1 0 50 Configurations C D E F

Natural Frequenciy (Hz)

Figure 9: Variation of the natural frequencies of 3D-printed PA6 plates with fully clamped boundary conditions and an aspect ratio of a/b =1.5 for various configurations.

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