Influence of process parameters on interlayer interface mechanical properties of 3D printing fiber reinforced concrete

• Firstly, this paper systematically studies the effects of various 3D printing processes on the mechanical properties of the interlaminar weak surface of 3D printed concrete components, and summarizes the correlation and law between the two. • Secondly, combined with the microscopic characterization detection, the mechanism of the printing process factors affecting the interlayer weak surface is analyzed, and the interoperability between the microscopic detection and the macroscopic test data is analyzed. • Finally, this paper proposes a prediction model for calculating the mechanical properties of interlayer weak surfaces of 3D printed concrete, which has an accuracy of more than 92% after a large number of experiments, which can provide a certain reference for practical use. The layer-by-layer deposition in concrete 3D printing creates weak interlayer interfaces, posing risks to structural integrity. This study systematically investigates the effects of printing parameters (layer height, speed, interlayer time intervals) and material composition on interlaminar tensile/shear strength and defect formation mechanisms using an experimental-computational approach. Results demonstrate that mechanical performance inversely correlates with layer height, printing speed, and interlayer intervals: reducing layer height from 15 mm to 5 mm elevates tensile strength by 186.85 %, while decreasing printing speed from 50 mm/s to 30 mm/s improves interlaminar tensile strength by 50.7 %. Continuous printing enhances interlaminar tensile and shear strengths by 77.18 % and 45.96 %, respectively, compared to 24-hour delayed printing. Microstructural analysis identifies crack width expansion as the primary cause of interfacial weakening. A mechanics-driven numerical model was established to quantify process-property relationships, predicting interlaminar tensile/shear forces with <5 % deviation from experimental measurements. Validation confirmed that the model can integrate and push out key parameters (layer height: 13–26 mm; Speed: 22–92 mm/s) for optimal bonding in line with industry specifications. This work provides a predictive framework for optimizing 3D-printed concrete structures by balancing process efficiency and interfacial durability, advancing the design of robust additive-manufactured construction components.