Anisotropic permeability and non-Newtonian flow in melt impregnation of thermoplastic composites

The growing demand for lightweight, high-performance materials has driven advancements in thermoplastic composites, widely used in aerospace and automotive industries. Efficient melt impregnation is crucial for optimizing composite quality and mechanical integrity. This study presents an enhanced mathematical model for the melt impregnation of thermoplastic composite addressing critical limitations in the existing framework that fails to accurately predict resin impregnation efficiency. Critical limitations in the existing framework that fail to accurately predict resin impregnation efficiency. Traditional models relying on Darcy's law inadequately capture the complex interactions between non-Newtonian resin dynamics and fiber matrices, limiting their accuracy in predicting impregnation efficiency. To overcome these challenges, the proposed model integrates the Navier–Stokes equation with the Herschel–Bulkley model, enabling comprehensive simulation of three-dimensional flow behavior and yield stress characteristics inherent to thermoplastic resin. The model also incorporates anisotropic permeability, fiber bed compaction, and energy dissipation due to fiber-resin interactions, offering nuanced insights into resin flow patterns and impregnation quality. Experimental validation was performed using MATLAB simulations with polypropylene reinforced by glass fibers. Rheological characterization and impregnation experiments under varying temperatures of 220–260°C demonstrated a strong correlation between experimental results and model prediction, with errors ranging from 1.4% to 2.6%. This research advances the theoretical understanding of non-Newtonian melt flow in composite manufacturing and provides a robust framework for optimizing process parameters, enhancing the mechanical integrity and performance of thermoplastic composites. Highlights: Enhanced model for melt impregnation of thermoplastic composites. Incorporates and Herschel–Bulkley equations. Accounts for anisotropic permeability and fiber bed compaction. Validated by MATLAB with minimal error (1.4%–2.6%).