Failure mechanics of fused filament fabricated nylon/carbon-reinforced composites

This work focuses on understanding the failure mechanisms of nylon-reinforced chopped carbon fiber (Onyx) composite and its reinforcement with carbon fiber printed using different infill patterns, i.e., solid fill, honeycomb, and triangular via fused filament fabrication (FFF) to enhance the sustainable manufacturing processes. The solid fill with carbon fiber reinforcement showcased a maximum tensile strength and flexural strength of ~ 300 MPa and ~ 22 MPa which were more than twice that of non-reinforced composites with fiber pull-out and layer debonding as predominant failure mechanisms. On the other hand, non-reinforced samples indicated matrix debonding as predominant failure behavior. The solid fill samples illustrated a lower failure mechanism owing to their higher bonding between each layer with limited voids whereas honeycomb and triangular samples failed faster due to the high number of voids limiting their bonding behavior. Furthermore, the load transfer capacity of honeycomb and triangular infill composites was limited due to reduced adhesion between the layers. Although the mechanical properties of onyx-based composites do not make them suitable for structural applications, the fused filament fabrication approach makes onyx a potential material for internal non-loading structures with complex geometries.