INFLUENCE OF PRINT PARAMETERS ON FRACTURE RESPONSE OF PLAIN AND FIBER-REINFORCED 3D-PRINTED BEAMS [Poster #21]

While much attention has been given to developing concrete mixtures for digital manufacturing (3D printing) and their associated rheological and mechanical properties, selecting appropriate printing parameters is also crucial for extrusion-based layered manufacturing. This paper explores the impact of layer height, a key parameter affecting rheology requirements, print quality, overall printing time, and interlayer bonding, on the flexural strength and fracture properties of 3D printed beams. This study investigates three-layer heights (LH) (5, 10, and 15 mm) corresponding to 25, 50, and 75% of the nozzle diameter (ND) (20 mm). The results show that smaller layer heights are more beneficial for both unreinforced and fiber-reinforced 3D printed mortars, despite the longer printing times and increased number of interfaces. Furthermore, adding a small amount of steel fiber reinforcement mitigates the adverse effects of weak interfaces on bulk properties. On average, flexural strengths are 30-40% higher, and fracture toughness and crack tip opening displacement are almost 30% higher than plain mixtures. The study employs strain energy release rates, digital image correlation, and optical images/micrographs to explain crack propagation in layered 3D printed mortars under unnotched four-point and notched three-point bending.
EXTENDED ABSTRACT