Effects of fiber layout on strength and failure of 3D printed notched composites

This study investigates the effect of printing strategies on the strength of additively manufactured notched fiber
reinforced composite specimens. Specimens with varying notch geometries (two radii and two opening angles)
and fiber layouts (unreinforced, unidirectional, quasi-isotropic and concentric) were 3D printed and tested under
tension. Digital image correlation provided surface strain field data. Results showed that fiber deposition patterns
significantly impact notch sensitivity, failure loads and mechanisms, with notch geometry being of secondary
importance. The unidirectional layout achieved the highest strength but with progressive failure, while quasiisotropic
specimens failed abruptly from the notch. The concentric layout shielded the notch region but
induced premature failure away from the notch due to transverse stress. Stress concentration factor approaches,
which work well for conventional laminates, have limitations for 3D printed composites due to local differences
and complex interactions. Optimizing fiber deposition, instead of geometry, emerges as a promising design route.
Combining unidirectional and contouring algorithms may improve performance. However, further studies utilizing
multiscale modelling and local failure analyses are needed to fully understand failure mechanisms and
guide optimal notch designs for 3D printed composites. With improved understanding and design methods, 3D
printing promises to unlock new possibilities for structurally efficient notched composite parts.