Enhancing polymer fiber orientation with 3D-printed shell–core structures

Abstract

This study numerically investigates the flow dynamics and fiber orientation in enhanced polymer shell–core structures during 3D printing using the smoothed particle hydrodynamics method. A microstructure-based fiber suspension model, coupled with a shear-thinning viscosity model, is employed to assess the effects of varying material viscosities, fiber aspect ratios and volume fractions, and substrate speeds on fiber orientation distribution. Our results demonstrate that fiber orientation in deposited layers is particularly sensitive to variations in the viscosity of the shell material, while changes in the core material viscosity have a smaller and more localized impact on fiber orientation. Furthermore, fiber orientation is strongly influenced by the product of the fiber aspect ratio α_r and volume fraction ϕ; as α_rϕ increases, fibers tend to align with the flow direction of materials. However, adjusting the fiber aspect ratio and volume fraction while maintaining the same α_rϕ results in slight changes to fiber alignment. Additionally, lower substrate speeds cause upstream material accumulation, increasing deposition layer height and creating differences in fiber orientation between the core and shell regions. An appropriate increase in substrate speed can mitigate these effects.