Effect of Infill Pattern and Density on the Mixed-Mode Fracture Behavior of 3D-Printed PLA/Carbon Composite Structures

The advances in 3D-printing technology add new dimensions to the already very versatile composite manufacturing methods. Polylactic acid (PLA) filaments are widely used for 3D printing. The low price and the biodegradability of PLA are major advantages; however, the lower fracture toughness is a drawback compared to conventional plastics, which are mass-produced with injection molding. The PLA/carbon filaments contain a 20% carbon volume ratio to increase the strength and the conductivity of the 3D-printed structures. The purpose of this study was to investigate the effects of infill pattern and density on the mixed-mode fracture behavior of 3D-printed PLA/carbon types of gyroid, cross, and triangle samples, with different infill percentages of 20%, 40%, and 60%. The type of failure displayed by the gyroid system resulted in higher fracture toughness values than those exhibited by the cross and triangle systems for all infill patterns under both mode-I and mode-II loadings. The enhanced fracture toughness and higher performance under mixed-mode loading in gyroid architectures compared to other systems indicate that they offer good resistance to crack propagation and present them as high-performance candidates for lightweight structural components. This study could offer a new path for printing parts based on fiber-reinforced polymer composites for several structural applications.