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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1. Introduction Ceramic materials are extensively utilized across multiple industries because of their advantageous properties, including strong resistance to high temperatures, exceptional mechanical strength, and durability against wear. They also perform well as thermal and electrical insulators. Furthermore, additive manufacturing enables the production of ceramic parts with intricate designs, from large components to detailed microstructures (Abdelkader et al., 2024). Several additive manufacturing methods are compatible with ceramic materials, including binder jetting, powder bed fusion, selective laser sintering (SLS), and material extrusion. This study focuses on material extrusion, specifically referred to as liquid deposition modeling (LDM) when applied to ceramics, as the material takes on an almost liquid state during production. The process starts with a clay-based paste that is extruded through a nozzle. In recent years, this technique has attracted growing interest from researchers, even for sintered and non-sintered clay products (Lamnini et al., 2022; Li et al., 2024). Even there are some studies that carried out a mechanical characterization of ceramic elements manufactured through LDM (Chaari et al., 2022; Cruz et al., 2020; Estévez & Abdallah, 2022; Finke et al., 2020), none of these studies have considered the anisotropy generated by the printing path. Therefore, this research aims to investigate the mechanical properties of ceramic products made using liquid deposition modeling (LDM), focusing on their behavior in the elastic regime and overall mechanical strength. The study specifically analyzes structures made of parallel lines, a common pattern in additive manufacturing that forms the walls of printed parts. It assumes that ceramics produced via LDM exhibit orthotropic behavior—meaning their properties vary along different directions—in relation to the printing path. This behavior is believed to result from discontinuities introduced during the printing process, including vertical joints between lines and horizontal joints between layers.

2. Materials and methods 2.1. Printing mixtures

This study focuses on two specific clay pastes sourced from quarries near the research location in Andalusia, Spain (Table 1). Various tests were conducted to assess the properties of the clay pastes used in the manufacturing process. The first set of tests evaluated the moisture content and consistency of the pastes at the water level used for printing, offering insights into their "printability." These tests, including water content and cone penetration as per ISO 17892-12:2018 standards, help determine the material's consistency.

Table 1 Printing mixtures used for sample fabrication

Printing material

Cone penetration ISO 17892 12:2018 standard (mm)

Water content (%)

Liquid limit (%)

Plastic limit (%)

Plasticity index

White clay (A) Red clay (B)

9,50 8,34

20,63

38 36

19 20

19 16

21,4

The water content of the clay pastes was measured by calculating the difference between their initial wet weight and their weight after drying the sample until it reached a stable mass (with less than 0.1% variation). The liquid limit, plastic limit, and plasticity index were determined following the guidelines of the ISO 17892-12:2018 standard. 2.2. Printing setup & test piece fabrication The prototypes are created using 3D clay printing via liquid deposition. For this process, a 5-liter Wasp 3D XL clay extruder has been adapted to an ABB IRB4600 robotic arm. The designs for the pieces are developed with Rhinoceros 3D CAD software, utilizing its Grasshopper plugin, which allows for Python scripting. Grasshopper is