Tough, High Impact Resistant 3D Printed Objects from Core-Shell Filaments

Fused deposition modeling (FDM), an extrusion-based 3D printing method, uses solid polymeric filaments. Typically, the polymers are formulated to provide desired characteristics and extruded into homogeneous filaments with well-defined diameter. However, an intrinsic weakness of FDM is the poor adhesion between printed layers with the bonding interfaces being poorly developed during printing. These poorly constructed interfaces lead to poor mechanical properties from FDM. Here, we propose a route to attack this intrinsic problem using core-shell structured filaments. The shell polymer is an ionomer and the core is polycarbonate (PC). The disparate solidification temperatures lead to the PC solidifying first to act as fiber reinforcement for shape control, while the ionomer generates a strong shell-shell interface between adjacent filaments. Samples printed from core-shell filaments show enhanced mechanical strength with samples that do not fail and an order of magnitude improvements in impact resistance. The mechanism for improvement is core-shell delamination energy dissipation, which is critical for inhibition of crack propagation. In addition to improvements in mechanical properties, the printed core-shell sample are less prone to warpage than the individual components.