Impact strength of 3D-printed polycarbonate

Abstract

A vertical wall printed by Fused Filament Fabrication consists of a ribbed surface profile, due to the layer wise deposition of molten plastic. The notches between the printed layers act as stress concentrators and decrease its resistance to impact. This article shows the relation between impact strength and layer height by experimental data and finite element simulations of the stress intensity factor and the plastic zone near the tip of the notch. The impact resistance increased from 6 to 32 kJ/m2, when the layer height was decreased from 1.8 to 0.2 mm. When notches were removed by sanding, the samples did not fail any more during impact testing, resembling the behavior of smooth molded test bars. Tensile strength values up to 61 MPa were measured independent of layer height. Birefringence measurements were done to determine the actual stress levels, which ranged from 2 to 5 MPa.