Multiscale reduced-order modeling of fused filament fabricated composites
Abstract
Defects such as voids are observed at multiple length scales of an additively manufactured composite material. Modeling such defects and their multiscale interaction is crucial for the materials performance prediction. In this work, we study as-built defects in fused filament fabricated Polycarbonate/Short Carbon Fiber (PC/SCF) composite samples. The microscale and mesoscale voids along with the mesoscale layer orientations have been studied using a mechanistic reduced-order model. Our result indicates that the microscale intrabead voids interact with the mesoscale interbead voids and significantly degrade the mechanical response of the printed composites compared to the microscale microstructure without voids. The mesoscale layer orientations also influence the stress-strain response and show better performance when the load is applied to the bead direction.
Summary
This paper is highly relevant for understanding the practical challenges of 3D printing carbon fiber reinforced composites using FDM. Key findings for DIY composite printing:
- Material System: Polycarbonate (PC) reinforced with Short Carbon Fibers (SCF) - a commercially available composite filament type
- Defect Types: Two main void types occur in FDM composites:
- Microscale intrabead voids (within the extruded bead)
- Mesoscale interbead voids (between beads/layers)
- Performance Impact: Voids significantly degrade mechanical properties compared to ideal microstructures
- Orientation Matters: Best mechanical performance when load is applied parallel to the bead/print direction
- Practical Implication: Print orientation planning is critical for structural composite parts
This research is useful for anyone using commercial carbon fiber filaments (like carbon fiber PETG or PC) and wanting to understand why printed parts may underperform compared to injection molded equivalents.