Enhancing Fiber Alignment and Tensile Properties of 3D-Printed Ultra-High Performance Strain-Hardening Cementitious Composites by Nozzle Channel Design (2026-01)¶

This study investigates nozzle channel designs to enhance fiber alignment and tensile properties in 3D-printed Ultra-High Performance Strain-Hardening Cementitious Composites (3DP-UHP-SHCC). Conventional rectangular nozzles ([5×30]) achieved moderate fiber alignment (14.1° average) but exhibited significant disparity between middle- (21.2°) and side-section fibers (10.6°), limiting tensile performance. Baffled nozzles ([5×30-I/II]) reduced the middle-section fiber angle by 59% (to 8.7°), but resulted in an increased nozzle pressure of 67.9 kPa, a 100% clogging risk, a 227% increase in porosity, and a 14.2% reduction in tensile strength. Novel V-shaped nozzles ([5×30-V180°/135°/90°]) addressed these issues by leveraging flow confinement and pressure gradients, aligning fibers without physical contact. The [5×30-V90°] nozzle achieved 11.3° middle-section fiber angle, 9.43 MPa strength, and 11.47% strain. The optimized N-shaped nozzle [5×30-N90°] delivered near-isotropic alignment (10.1° middle section, ≤0.5° deviation) and superior tensile performance: 9.93 MPa (+17.8%) strength and 11.76% (+15.7%) strain. Results demonstrate that geometric nozzle optimization enhances fiber alignment and tensile properties while maintaining extrusion reliability.