Evaluating the Effect of Z-pinning Parameters on the Mechanical Strength and Toughness of Printed Polymer Composite Structures

Traditional Fused Filament Fabrication methods create a mechanically anisotropic structure that is stronger in the deposition plane than across successive layers. A recently developed pinning process deposits continuous pins in the structure that are orientated in the build direction across multiple layers. Initial studies of this technique have demonstrated the ability to increase inter-layer strength and toughness. The current study evaluated various z-pinning parameters for carbon fiber reinforced polylactic acid (CF-PLA) structures, including infill percentage, pin length, and deposition pattern. Each of these was found to affect the ability of the z-pin to mechanically bond with the existing lattice structure and had a resulting impact on the mechanical strength and toughness. Initial studies showed an increase in ultimate tensile strength in the Z-axis of around 3.5x. Upon expanding the pinning settings, further studies showed increases of over 35% from the X and Z axis ultimate tensile strength and improved mechanically isotropic behavior.