PSI - Issue 77

Pawel Madejski et al. / Procedia Structural Integrity 77 (2026) 323–330 Author name / Structural Integrity Procedia 00 (2026) 000–000

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3.1.5. Yield, Ultimate Tensile, and Failure Strength point

The tensile behavior of PLA specimens produced with different 3D printing infill patterns was systematically evaluated. Some mechanical properties, such as yield strength, ultimate tensile strength, failure strength, and strain at maximum load, were obtained from stress–strain analyses (Figure 8).

Figure 8. Yield, Ultimate Tensile and Failure Strength points of different infill geometries.

A comparative evaluation of the infill patterns reveals that mechanical performance is significantly influenced by infill geometry. The octet and quarter cubic structures enhance both strength and ductility relative to the more conventional cubic and triangle designs. In contrast, line infill, despite its lower yield strength, offers the greatest ductility, which can be advantageous for parts subjected to intermittent or impact loads. The observed trends reflect how infill geometry alters the deformation and failure mechanisms of PLA under tensile loading. Structures with interconnected pathways (e.g., octet) better distribute stress and delay failure, while simpler patterns (e.g., triangles) localize strain, resulting in less ductility. 3.2. Thermal conductivity and effusivity of PLA with different infill geometries The thermal characterization of 3D printed PLA specimens reveals significant variations in thermal properties across different infill geometries. These values were obtained using a Trident device via Modified Transient Plane Source (MTPS) sensor, while density was calculated by considering the diameter, thickness, and mass of disc samples used for thermal conductivity measurement. The obtained density values were subsequently used to calculate the specific heat capacity. The obtained thermal conductivity and effusivity values, along with the calculated density and specific heat of the disc samples used for thermal conductivity measurements, are presented in Table 1. Table 1 Measured mean value of thermal conductivity and effusivity of PLA samples with different infill geometries and their calculated density and specific heat. Group Thermal Effusivity (W·s¹ ᐟ ²/m²·K] Thermal Conductivity (W/m·K) Density (kg/m³) Specific heat (J/kg·K)

Cubic Lines Octet

855.2 702.8 742.6 702.8 1203.6

0.495 0.344 0.383

1231.82 1252.11 1226.25 1224.98 1188.91

1199.21 1145.07 1173.55 1185.92 1403.77

Quarter cubic

0.34

Triangle

0.868