Continuous fiber-reinforced composite 3D printing (CFRC 3DP) has become a hot topic of interest for many experts and scholars. Continuous fiber-reinforced prepreg filament (CFRPF) for printing needs to be prepared in advance. In this paper, on the basis of the resin fusion impregnation theory, a fabrication device was designed for continuous carbon fiber-reinforced polycarbonate prepreg filament (CCFRPF). Then, according to the orthogonal test and the TOPSIS entropy weight optimization theory, the optimization method for CFRPF/PC preparation process parameters was proposed, and the relationship between the preparation process parameters and the performance indexes was discussed. The results show that when preparing CCFRPF/PC, the weight of diameter performance index is the largest, about 0.75. The optimal combination of process parameters for CCFRPF/PC is, respectively, 285 °C for the outlet mold temperature, 305 °C for the impregnation mold temperature, and 1 m/min for the winding speed. In this case, the diameter, roundness, minimum curvature radius and tensile strength of 0.375 mm, 29.4 μm, 9.775 mm and 1298 MPa were achieved, respectively.

3D-printed short-carbon-fiber-reinforced thermoplastic composites have attracted significant attention from both the academic and industrial communities due to their remarkable advantages such as lightweight, high strength, and recyclability. However, in most of the current 3D-printing-related nylon composites, the content of short carbon fibers is generally low, and the influence laws of short carbon fibers on the mechanical properties of the composites have not been fully explored. This paper focuses on short-carbon-fiber-reinforced nylon (SCF/PA) composites with short-carbon-fiber contents of 15 wt%, 25 wt%, and 35 wt%, respectively. It studies in depth their mechanical properties and related characteristics. The research results show that with the increase in the short-carbon-fiber content, the melt flow rate of the SCF/PA composites shows a downward trend. In terms of mechanical properties, when the short-carbon-fiber content is 25 wt%, the tensile strength and flexural strength of the composite reach their maximum values, which are 101.43 MPa and 173.16 MPa, respectively. Compared with pure nylon, the improvement ranges are 17.01% and 21.4%, respectively. When the short-carbon-fiber content is 35 wt%, the impact resistance of the material reaches its optimal value, which is 6.02 KJ/m², an increase of 38.1% compared with pure nylon. At the same time, when the short-carbon-fiber content is 35 wt%, the thermal deformation temperature of the material also shows a certain degree of slight increase. In summary, the research results of this paper will provide more abundant and detailed experimental data support for 3D-printed short-carbon-fiber-reinforced nylon composites in various different application scenarios, facilitating further exploration and application in related fields.

The efficient and cost-effective residual stress control method is of great significance for the application of additive manufacturing (AM) technology. In this work, thermal-vibration stress relief (TVSR) with different temperatures and dynamic stresses was performed on Ti6Al4V samples prepared by selective laser melting (SLM), the stress relief effects of TVSR and its influence on phase and microstructure were investigated and compared with thermal stress relief (TSR) and vibration stress relief (VSR), and the stress relief mechanisms of these methods are discussed. It was found that the residual stress relief rate can reach 86.76% after TVSR treatment at a temperature of 380 °C and a dynamic stress of 400 MPa, which increased by 63.63% compared with VSR under the same dynamic stress. The efficiency is increased by 76% compared with TSR at 580 °C and the residual stress relief rate is almost the same. After TVSR, VSR and TSR treatments, the grain morphology, size and phase content of samples were basically unchanged, and low-angle grain boundaries (LAGBs) were increased after TVSR and VSR treatments and decreased after TSR treatment. The results confirm that the TVSR method has the ability to control the residual stress of selective laser melted Ti6Al4V with low time and cost consumption, and are helpful for engineering applications of TVSR.

Fused filament fabrication (FFF) 3D printing technology for continuous fiber-reinforced composite (CFRC) printing has become a trend. This article is based on ‘independent extrusion’ FFF CFRC printing. The continuous fiber-reinforced filament (CFRF) printing solution is the contour offset method for obtaining executable g-code. When the CFRCF prints at the corner, it is found that the actual CFRC printing trajectory is inconsistent with the ideal laying trajectory. The causes of the error are analyzed, and an angle optimization algorithm is proposed. The corner optimization algorithm is verified by theoretical analysis and experimental analysis. From the experimental results, the corner optimization algorithm improves the 30° angle fit of CFRF printing by 90% and reliability has also been improved. When the printing length is 127,200 mm, there are 960 printing corners, and the failure rate is 0.

Successful continuous fiber-reinforced composite filament 3D printing hinges on the synergistic relationship between the printing nozzle and precisely controlled process parameters. This research uses a simulation model to investigate how printing temperature, printing speed, and nozzle length affect the prepreg filament’s molten state during 3D printing. We employed the Box–Behnken response surface methodology to optimize these key parameters. Using continuous fiber-reinforced composite filament polylactic acid (CFRCF/PLA) as an example, and a printing nozzle with a 1 mm diameter and an 8 mm length of heating zone were designed. The optimal printing parameters were determined to be as follows: printing temperature of 220 °C, printing speed of 300 mm/min, and printing layer height of 0.2 mm. Experimental validation using the optimized nozzle and parameters demonstrated enhanced stability in continuous fiber prepreg filament printing.

To enhance the aerodynamic performance of centrifugal impellers, this study presents an advanced optimization design methodology. This methodology addresses the challenges associated with numerous design variables, inflexible configurations, and low optimization efficiency. We propose two distinct spline function parameterization techniques: a global mapping model for Bezier surfaces and a local mapping model for Free-Form Deformation (FFD) control bodies. We investigate the impact of these parameterization methods on blade geometry configuration and aerodynamic performance. By integrating these two parameterization approaches with multi-objective evolutionary algorithms and Computational Fluid Dynamics (CFD) techniques, we enable global and local optimization of centrifugal compressor blades. The optimization results demonstrate a 1.77% enhancement in isentropic efficiency under rated operating conditions, a 7.8% increase in surge margin, a 1.6% improvement in isentropic efficiency under normal operating conditions, and an 11.8% enhancement in surge margin. Through two optimization stages, the optimization space for blade geometry is thoroughly explored, enhancing solution quality and contributing to the advancement of impeller mechanical optimization design theory.