Torsional performance and failure analysis of FFF carbon fiber-reinforced PLA: An experimental study

Additive Manufacturing (AM), particularly fused filament fabrication (FFF), is redefining production through customization and lightweight design. However, the torsional behavior of carbon fiber-reinforced polylactic acid (CF-PLA) under varying printing parameters remains undetermined, limiting its reliable use in advanced engineering systems. This study systematically investigates the effects of FFF process parameters (raster angle, layer height, and infill density) on the torsional performance of CF-PLA. A factorial experimental design with ANOVA and regression modeling quantified main and interaction effects on shear modulus, yield strength, and ultimate shear strength. Multi-response optimization improved shear modulus by ~ 14.4%, yield strength by ~ 41.5%, and ultimate shear strength by ~ 39.6%, whereas decreased failure strain by ~ 77.3%. Scanning electron microscope (SEM) fractography revealed micro-structural failure modes. The results demonstrate that careful parameter selection (0° raster orientation, reduced layer height, and increased infill density) substantially enhances the torsional reliability of CF-PLA parts for high-performance applications.