Abstract: In various embodiments the invention is directed to a structured filament for use in fused filament fabrication comprising an inner core comprising an first polymer or polymer blend; and an outer shell surrounding said inner core comprising a second polymer or polymer blend having ionic or crystalline functionality; wherein said first polymer or polymer blend has a higher solidification temperature than said second polymer or polymer blend. The ionic or crystalline functionality of the outer shell material strengthen the interface between the printed layers. This structured filament leads to printed 3D structures having improved dimensional fidelity and impact resistance in comparison to the individual components. The impact resistance of structures printed from these is greatly increased as energy is dissipated by delamination of the shell from the core near the crack tip, while the core remains intact to provide stability to the part after impact.