Investigating Process-Structure-Property Relationships in Large-Scale Additively Manufactured Carbon-Filled PETg

Properties of a material fabricated by large-scale additive manufacturing exhibit strong process dependence by way of processing and microstructure. This study seeks to experimentally evaluate this process-structure-property linkage for carbon-fiber-reinforced PETg. To facilitate this investigation, an experimental design involving eight different combinations of layer height, feed rate, bead spacing and screw speed in the printing process is considered. Forty-five microstructure specimens are excised and imaged to reveal the fiber orientation and porosity, and nearly 180 flexural samples are tested to evaluate their strength and stiffness. Measured mean values for modulus along the bead range from 13.3 to 18.6 GPa, and for strength, it is between 158 to 189 MPa. Mean values for the inter-layer stiffness range from 2.9 to 3.2 GPa, and for strength, it ranges between 31.4 and 45.0 MPa. Results indicate a strong relationship between screw speed and fiber orientation and between fiber orientation and stiffness and strength. Additional insights into the fracture behavior of the material are provided using high-speed photography of the moment of fracture and microscopy of the fracture surfaces. This work provides a cohesive process-structure-property dataset that can be used as a reference for validation of process-structure, structure-property, and process-structure-property models.