Single-Screw Extrusion of Polymer Composites

Overview
Developed a unified DEM–FEM–analytical modeling framework during my Ph.D. to predict pellet motion, melting, deformation, and fiber breakage for long-discontinuous fiber-reinforced polymer pellets. This work appears in my thesis and related publications (Kapre, 2024), (Kapre et al., 2025), (Kapre et al., 2024).

DEM pellet trajectories, melt progression, and fiber-length distribution along the screw.

Approach

DEM (LIGGGHTS) for pellet motion and kinematics
FEM (ABAQUS) for heat transfer and melting of individual pellets
Beam theory + Weibull model for pellet deformation and fiber breakage
Coupled these into a melt progression + fiber-length evolution framework

Predicted fiber-length distributions and melt-state evolution along the screw.

Key Results

Pellets recirculate primarily in the second half of the screw, aligning with rapid outside–in melting
Fiber breakage initiates once the outer pellet layer melts
Starve-feeding reduces residence time and fiber attrition; high RPM can cause incomplete melting
Predicted bimodal fiber-length distributions match experiments

Impact
Provides a quantitative basis to tune screw geometry, feeding mode, and processing conditions to preserve fiber length and improve composite performance; extensible to other thermoplastic and extrusion-based AM feedstocks.

Tools
LIGGGHTS, ABAQUS, MATLAB, Python, HPC environment; Material: 40% CF-PPS

References

2025

2024