Investigation of the structural performance and failure mechanisms of 3D printed continuous carbon fiber-based composites

Additive manufacturing of continuous fiber-based polymeric composites has attracted global attention. This contemporary technology enables the flexibility of manufacturing customized, partially and fully functional, and advanced composite components for numerous semi-structural and structural applications. The current study investigates the structural performance of 3D-printed carbon fiber-based composites in the context of tensile, flexural, and high-cycle fatigue. The crucial S-N curves for the unidirectional (UD) (0°) and cross-ply (CP) (0, 90) composites have been plotted. The dominating failure mechanisms responsible for the failure of 3D printed composites under tensile, flexural, and high cycle fatigue loading at the micro-scale have been thoroughly investigated. The influence of fiber orientation on the failure mechanisms under different structural loading has been rigorously studied. The current findings conclude that cross-ply (0, 90) composites exhibited superior fatigue performance than the unidirectional composites when investigated at 70% of their ultimate tensile strength. The current investigation reveals that the formation of voids during 3D printing and majorly during loading is one of the leading causes of the failure of additively manufactured composites under mechanical and cyclic loads. The fiber pull-out, fiber breakage, de-bonding, and voids are the dominating failure mechanisms observed under tensile loading. In addition to the failure mechanisms listed under tensile loading, matrix fractures have also been observed under flexural loading. The dominating failure mechanisms differed for UD, CP (0, 90), and CP (45, −45) composites. Highlights: Investigated tensile, flexural, and fatigue properties of continuous fiber 3D-printed composites. Examined failure mechanisms under tensile, bending, and fatigue loading. Developed test coupons with built-in tabs for tensile and fatigue testing. Cross-ply composites showed better fatigue performance than unidirectional.