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Additive Manufacturing of Bio-Based PA11 Composites with Recycled Short Carbon Fibers: Stiffness-Strength
Christian Brauner1, Thierry Bourquin1, Julian Kupski1
1Institute of Polymer Engineering, FHNW University of Applied Sciences and Arts Northwestern Switzerland, Klosterzelgstrasse 2, 5210 Windisch, Switzerland.
Polymers
|September 27, 2025
Summary
This study developed sustainable, high-stiffness short carbon fiber composites using bio-based polyamide 11 for Additive Fusion Technology (AFT) 3D printing. AFT printing achieved mechanical properties comparable to injection molding, demonstrating a viable sustainable manufacturing approach.
Area of Science:
- Materials Science
- Polymer Engineering
- Additive Manufacturing
Background:
- Bio-based polyamide 11 (PA11) offers a sustainable alternative to petroleum-based polymers.
- Short fiber composites are attractive for their balance of properties and processability.
- Additive Fusion Technology (AFT) enables complex geometries but requires optimized material formulations.
Purpose of the Study:
- To develop and characterize short carbon fiber-reinforced bio-based PA11 composites for AFT 3D printing.
- To benchmark the performance of AFT-printed composites against injection-molded counterparts.
- To investigate the influence of fiber alignment on mechanical properties and anisotropy.
Main Methods:
- Extrusion of 1.75 mm diameter filaments with 15% and 25% recycled carbon fibers (rCFs).
- AFT 3D printing and subsequent consolidation of composite parts.
- Mechanical testing (tensile, impact) and dynamic mechanical analysis (DMA).
- Microstructural analysis comparing AFT printing and injection molding.
Main Results:
- Successfully extruded filaments up to 25 wt% rCFs; higher content caused brittle failure.
- AFT printing produced highly aligned fibers, leading to superior axial stiffness (14.5 GPa at 25 wt% rCF) compared to injection molding (11.0 GPa).
- Pronounced anisotropy observed in AFT parts: transverse properties were significantly lower than axial properties.
- Impact toughness varied with orientation; AFT 90° samples showed higher energy absorption.
Conclusions:
- AFT 3D printing of bio-based PA11 with rCFs is feasible, yielding high-stiffness composites.
- Aligned short fibers in AFT parts offer performance comparable to injection molding, with anisotropy as a key design consideration.
- This work pioneers the use of sustainable, short fiber composites in additive manufacturing for demanding applications.
