Effect of infill patterns on carbon nylon 3D-printed composites under ballistic impact

Abstract The purpose of this study is to evaluate the impact of different infill patterns on the mechanical and ballistic behaviour of 3D-printed carbon-nylon composites. The carbon nylon material was used to print samples with different infill patterns such as (Tri-Hexagon, Cubic, and Gyroid) and with an infill density of 80%. The mechanical tests such as tensile, flexural, impact, and interlaminar shear strength (ILSS) were examined on the printed samples. The results have shown that the gyroid pattern had shown better performance in mechanical characteristics. The mechanical characteristics of 3D printed samples with gyroid pattern showed improvements of 16.63% in tensile strength, 5.64% in flexural strength, 6.52% in impact strength, and 16.72% in ILSS respectively in contrast with tri-hexagon infill pattern. Micrograph evaluation was done on the damaged surfaces of tensile and flexural tested specimens. The microscopy image of the gyroid pattern’s fractured surface has revealed improved bonding, minimal voids, and no delamination, which may be the cause of the increase in mechanical properties. Besides, the micrograph image revealed that more voids in the cube pattern, are considered to be responsible for its lower mechanical performance. The high-velocity impact test was done to examine the energy absorption behaviour and damage propagation of 3D printed samples with an infill density of 80%. The findings revealed that the gyroid pattern improved their impact resistance. The ballistic impact test results show that the gyroid pattern affords better energy absorption because of its continuous structure, and efficiently disperses impact energy throughout the sample’s entire volume. The printed samples with the gyroid pattern showed a 5.24% rise in energy absorption than the cube pattern. The optimal infill density and infill pattern could be used to make materials for impact applications due to their better mechanical and energy absorption abilities.