Multi-factor optimization of impact energy absorption and failure mechanisms in additively manufactured carbon-nylon composites
Academic Article in Scopus
The impact performance of fused filament fabricated carbon-fiber-reinforced nylon components is strongly governed by interactions among processing parameters, internal architecture, and fracture mechanisms. In this study, the absorbed impact energy of additively manufactured notched PA12-CF specimens was evaluated using a Taguchi experimental design considering six processing factors at five levels: bridge direction, infill pattern, nozzle temperature, build plate temperature, infill density, and layer thickness. Five replicate specimens were tested for each of the 25 experimental conditions using a Hounsfield balanced-impact machine, yielding 125 impact tests. The Taguchi analysis identified infill density, bridge direction, and layer thickness as the dominant factors controlling energy absorption, while infill pattern had a secondary but relevant effect. In contrast, nozzle temperature and build plate temperature showed comparatively lower contributions within the evaluated range. The highest response within the original Taguchi matrix was obtained for a 30° bridge direction, aligned rectilinear infill, 280 °C nozzle temperature, 43 °C build plate temperature, 100% infill density, and 0.08 mm layer thickness, reaching 3.42 ± 0.07 J. A regression-based full factorial analysis predicted an untested optimum consisting of a 30° bridge direction, Rectilinear infill, 280 °C nozzle temperature, 43 °C build plate temperature, 100% infill density, and 0.08 mm layer thickness. Five confirmation specimens fabricated using this parameter combination achieved 3.76 ± 0.04 J, differing by only 2.1% from the predicted value and representing the highest absorbed impact energy measured in this investigation. SEM fractography revealed that high-energy configurations were associated with improved local continuity beneath the printed notch, more tortuous crack trajectories, enhanced ligament tearing, and interlayer fusion. Conversely, low-energy specimens exhibited local discontinuities, weak propagation paths, and more direct fracture trajectories. Overall, the results show that maximizing impact absorption in printed PA12-CF requires not only increasing material density but also controlling the spatial arrangement of deposited roads and the local fracture resistance around the notch.
