BUAA: In-situ monitoring enables precise deformation prediction in 3D printing of composite materials.

September 26, 2025 Materials 167

Beijing University of Aeronautics and Astronautics: Process Modeling and Deformation Prediction for 3D Printed Continuous Fiber-Reinforced Composites Based on In-Situ Micro-Scale Measurement

3D printing technology for continuous fiber-reinforced thermoplastic composites (CFRTPCs) has garnered significant attention in the aerospace sector due to advantages such as lightweight properties and high specific strength. However, deformation caused by residual stress during the printing process has long hindered its engineering application. Existing research faces three major limitations: the lack of in-situ measurement of microscopic temperature gradients in the prepreg filament, neglect of the influence of printing force fields (pressure/tension) on residual stress, and the difficulty of single-scale modeling methods in simultaneously accurately simulating the transient temperature field during extrusion and the stress field during printing. These issues lead to deformation prediction errors as high as 20%.

To address these challenges, the research team from BUAA proposed a multi-scale process modeling method. A key innovation was the development of a temperature-sensitive prepreg filament: ultra-fine thermocouples with a diameter of 100μm were embedded during the compounding of Toray T800H carbon fiber and PA6 nylon, enabling micro-zone temperature tracking throughout the entire process from extrusion to cooling. The study also established an in-situ force field monitoring platform, collecting layer-thickness-related pressure/tension data via thin-film pressure sensors and force sensors. Based on the measured data, the team developed a coupled extrusion-printing model: first, the filament geometry inside the nozzle was reconstructed using CT scanning to simulate the transient temperature field during extrusion; then, combined with the "element birth and death" technique, temperature, pressure, and tension boundary conditions were dynamically applied to predict residual stress and deformation.

Experimental results demonstrated that this model controls deformation prediction error within 5%, significantly outperforming traditional methods. The research, for the first time using embedded thermocouples, identified the nozzle-filament contact zone as the primary heat-affected zone and quantified the influence of parameters like material thermal conductivity and printing temperature on temperature gradient and residual stress. This work provides theoretical support and a low-cost optimization pathway for high-precision 3D printing of CFRTPCs.

Flowchart of the data measurement and simulation methodology for the 3D printing process.

Temperature-sensitive prepreg filament fabrication process: (a) schematic diagram, (b) resin impregnation process, (c) main equipment components and cross-section of the temperature-sensitive prepreg filament.

(a) Schematic of in-situ printing temperature measurement, (b) schematic of the in-situ printing force field monitoring platform.

(a) Cross-section of the temperature-sensitive prepreg filament, (b) temperature measurement point distribution, (c) temperature data during the printing process.

(a) Method for characterizing fiber orientation within the nozzle, (b) characterization and 3D reconstruction results.

Finite element model of the extrusion process: (a) overall model, (b) local section of nozzle contacting prepreg filament, (c) main heat-affected zone of the prepreg filament, (d) spatial correspondence between the finite element model and experimental measurement points.

(a) Static simulation of the extrusion process, (b) dynamic simulation of the printing process, (c) Gaussian surface fitting for different isothermal cross-sections.

Force field measurement system data: (a) printing tension, (b) printing pressure.

(a) Internal residual stress at the end of printing, (b) stress release results after detachment from the substrate, (c) Z-direction displacement after detachment from the substrate.

Original Reference:
Ouyang S, Li D, Zhu W, et al. Process modeling and deformation prediction of 3D printed continuous fiber-reinforced composites based on in-situ micro-scale measuring[J]. Composites Science and Technology, 2025, 267: 111209.

Link: https://doi.org/10.1016/j.compscitech.2025.111209