Predicting strength of thermoplastic polymer parts produced using additive manufacturing

The weakest point in polymer parts produced by Fused Filament Fabrication (FFF) is the interface between adjacent layers and deposition toolpaths, or “roads”. We introduce a novel approach that uses the temperature history of these interfaces, polymer rheological data, and polymer welding theory to predict the mechanical strength of parts subjected to uniaxial tension. Interface temperature history data is collected in-situ using infrared imaging. Rheological data of the polycarbonate (PC) used to fabricate the parts in this study was determined experimentally. The prediction of strength of the interfaces was performed using polymer weld theory from the literature adapted to the PC feedstock used in this study. Understanding how the strength of the road and layer interfaces develop mechanical strength will lead to stronger FFF parts through intelligent toolpath optimization and temperature control.