Interrelationships between process parameters, cross-sectional geometry, fracture behavior, and mechanical properties in material extrusion additive manufacturing

Abstract

Additive manufacturing offers reduced lead time between design and manufacturing. Fused filament fabrication, the most common form of material extrusion additive manufacturing, enables the production of custom-made parts with complex geometry. Despite the numerous advantages of additive manufacturing, reliability, reproducibility, and achievement of isotropic bulk properties in part remains challenging. We investigated the tensile behavior of a model polycarbonate system to explore what leads to different tensile properties, including sources of ductile versus brittle fracture. We utilized a one factor at a time (OFAT) design of experiments (DOE), printed single road-width boxes, and performed tensile tests on specimens from these boxes. Additionally, we characterized the cross-sections of parts printed under different conditions and their subsequent fracture behavior. The results demonstrate that isotropic bulk properties are achievable by printing at high speeds, and provide mechanisms to explain why. Highlights: Printing at high speeds leads to improved mechanical properties. Printed samples undergo a mix of ductile and brittle failure. Jagged fracture path is associated with superior adhesion. High layer times lead to worse interfacial bonding.