PSI - Issue 68

Masoomeh Farrokhtar et al. / Procedia Structural Integrity 68 (2025) 592–595 Masoomeh Farrokhtar et al. / Structural Integrity Procedia 00 (2025) 000–000

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production of co-axial core-shell structures made of 316L steel and diverse ceramics, Biasetto et al. (2021), Biasetto et al. (2023). The microstructural (crystalline phases) geometrical (e.g. residual porosity) and mechanical characteristics of the additively manufactured parts depend on production parameters like: ink composition, quality of the printed part, de-binding and sintering conditions. The effectiveness of the coupling depends also on the metal ceramic interface properties, which are difficult to determine directly, Bolzon and Pitchai (2021), Maier et al. (2006). The results of bending tests performed on homogeneous and composite samples have therefore been interpreted with the aid of a numerical model of the experiment, as frequently done in the case of complex material systems, e.g. Amani et al. (2020), Gavazzoni et al. (2021), Lienhard et al. (2023). 2. Experimental Program Core-shell structures consisting of 316L stainless steel surrounded by different ceramics (Al 2 O 3 and CaTiSiO 5 ) were created through co-axial DIW and sintering. Al 2 O 3 was used to understand the effect of core-shell interface on the composite mechanical properties whilst CaTiSiO 5 was used to produce bio-composites capable of improved toughness and bio-activity. The temperatures involved in this process can significantly affect strength influencing factors such as density, residual porosity, grain size, so as secondary phases formation and precipitation. A wide experimental program has been therefore implemented. Several composite and homogeneous metal and ceramic filaments have been produced, with the geometries represented in Fig. 1. The overall dimensions of the core-shell filaments are approximately 40 mm in length and 1.4 mm in total diameter, while the diameter of the metal phase depends on the injection pressure.

Metal Core

Ceramic Core

Ceramic Shell

Metal Core-Ceramic Shell

Fig. 1. Homogeneous and composite filaments

All samples have been subjected to small-scale Four-Point Bending Test (4PBT) under displacement control at 0.5 mm/min rate. The experimental setup and the typical output of the tests performed on composite filaments are represented in Fig. 2.

Fig. 2. 4PBT: setup and typical load-displacement curve of the composite filaments

The alumina samples presented a brittle response with tensile strength almost independent of the sintering process and specimen geometry and size. In contrast, the characteristics of the printed metal filaments were strongly influenced