PSI - Issue 68

A. Jiménez et al. / Procedia Structural Integrity 68 (2025) 603–609 Adriano Jiménez et al. / Structural Integrity Procedia 00 (2025) 000–000

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3.1.2. Compression tests The chart (Fig. 4, center) displays compressive strength data from unconfined compression tests, measured in megapascals. Despite variation in the results, all three test batches consistently show a decrease in compressive strength based on the print path direction, indicating anisotropy. Regarding the average increase in compressive strength relative to the X direction, the material exhibits orthotropic behavior: the Y direction is generally the weakest (49 to 85% of direction X strength), followed by the Z direction (80 to 105% of direction X strength), so that, the X direction is almost always the strongest.

Fig. 4. Results of the tests conducted on batches A6, B6 & B8: Flexural strength from the three-point bending test (left); compressive strength from the unconfined compression tests (center); pulse velocity obtained from the ultrasound tests (right). 3.1.3. Ultrasonic tests Like the mechanical tests, the ultrasound measurements (Fig. 4, right) reveal a clear difference in pulse velocity depending on whether the pulse travels parallel to the printing path (X), perpendicular in the horizontal plane (Y), or perpendicular in the vertical plane (Z). The variation in direct pulse velocity is minimal, even when comparing different batches made with varying clay pastes, nozzles, and printing parameters. This indicates that the direct pulse velocity is consistent in the same direction and clearly distinct from the other two directions. 4. Conclusions This study explores the mechanical behavior of ceramic materials produced using Liquid Deposition Modeling (LDM), focusing on the influence of the printing path on the material’s mechanical properties. The experimental analysis demonstrates that ceramic structures exhibit orthotropic behavior due to the anisotropy introduced by the layer-by-layer manufacturing process. The results from the mechanical tests reveal that discontinuities, such as joints between printing lines and layers, serve as fracture initiation points. Specimens with load paths perpendicular to the printing lines generally exhibited higher flexural and compressive strengths compared to those aligned with the printing lines. Notably, the X direction (perpendicular to the printing path) consistently showed stronger performance than the Y and Z directions, indicating a distinct orthotropic behavior. This is further supported by the ultrasonic and microstructural analyses, which confirmed the presence of pores and defects introduced during the printing process, particularly between the printing lines.