Effect of infill pattern on bending and impact behaviour of 3D printed sandwich beams

Poly lactic acid (PLA), used in green materials, is the most used polymer in scientific studies, especially in 3D printing production, with its low density and high strength value. PLA also finds a lot of application areas in sandwich beams where mass comes to the fore. The sandwich beams in this study were produced with 3D printing using different infill patterns. To investigate the effect of these patterns, bending and Charpy impact tests, which are most used in the characterization of sandwich beams, were performed. The obtained bending module, bending strength, bending displacement, Charpy impact energy and Charpy impact strength were examined in detail. The mass of the sandwich beams varied significantly with infill pattern, where cubic subdivision, concentric, and cross 3D patterns reduced the mass by approximately 10%, while the lightning pattern achieved a mass reduction of about 45% compared to conventional infill geometries. The concentric infill pattern provided the highest bending performance, showing approximately 28–30% higher bending stiffness and strength than most other patterns despite having about 10% lower mass, whereas the lines and lightning patterns exhibited the lowest stiffness due to limited structural connectivity. In Charpy impact testing, the concentric pattern exhibited the highest impact energy, followed by the lines pattern, which showed comparably high energy absorption, while highly discontinuous patterns such as lightning resulted in markedly lower impact resistance.