Portal Contents
FDM Mechanisms
In-situ fusion, dual extruder, ex-situ prepreg, and modified printing approaches including 3D compaction printing.
Fiber Types
Synthetic fibers (Carbon, Glass, Kevlar/Aramid) and natural fibers (Flax, Hemp, Kenaf, Basalt, Cotton).
Matrix Materials
Thermoplastic polymers: PLA, ABS, Nylon/PA, PETG, PC, TPU, PP, PEEK and their properties.
Research Teams
Active labs and researchers at University of Tehran, Tokyo University of Science, Xi'an Jiaotong, and more.
Top Journals
Primary publication venues: Composites Part A/B, Additive Manufacturing, Polymers, and more.
Overview
FDM is an additive manufacturing technology that fabricates 3D objects by depositing thermoplastic filaments layer-by-layer through a heated nozzle. While FDM offers advantages including ease of use, low cost, and minimal material waste, 3D-printed FDM components exhibit lower strength compared to conventionally manufactured parts due to high porosity and low inter-layer adhesion.
To address these limitations, reinforcing fibers are added to the polymer matrix. Continuous fibers can transfer and retain loads within unbroken strands, reducing the load applied to the polymer matrix and leading to higher load-bearing capacity than short fiber composites.
| Fiber Type | Characteristics | Mechanical Performance |
|---|---|---|
| Discontinuous (Short) | Random orientation, aspect ratio <1000, max 50% volume fraction | Limited strength improvement due to matrix-dependent load transfer |
| Continuous | Preferred orientation, long aspect ratio, direct load transfer | Higher strength due to unbroken fiber strands retaining loads |
FDM Mechanisms Summary
1. In-Situ Fusion Mechanism
Both reinforcing fiber and neat polymer matrix are combined during printing through a single nozzle ("nozzle impregnation"). The dry fiber feedstock is drawn into the nozzle and preheated while the matrix polymer is introduced into the melt zone.
Advantages: Single-step manufacturing, user control over thermoplastic flow rate, lower equipment cost
Disadvantages: Poor layer bonding, inadequate polymer infusion, increased porosity
2. Dual Extruder / Ex-Situ Prepreg
Uses two extruders: one deposits the pure polymer filament, the other deposits pre-impregnated (prepreg) reinforcing filament. Companies like MarkForged and Anisoprint produce commercial prepreg filaments.
Advantages: Greater flexibility and precision, control over fiber position, enables different material combinations
Disadvantages: Higher equipment cost, more filament consumption, time-consuming setup
Mechanical Properties
Synthetic Fiber Composites
| Matrix | Fiber | Volume % | Key Results | Reference |
|---|---|---|---|---|
| ABS | Carbon | 6.5% | Flexural strength 127 MPa, UTS 147 MPa | Yang et al., 2017 |
| PLA | Carbon | 27% | Bending strength 335 MPa, modulus 30 GPa | Tian et al., 2016 |
| PLA | Carbon | 34% | 14% tensile, 164% bending strength increase vs unprocessed | Li et al., 2016 |
| Nylon | Carbon/Glass/Kevlar | 26.8-73.4% | Highest shear strength for carbon fiber | Caminero et al., 2018 |
| PETG | Aramid | 45% | +1550% modulus, +1150% strength vs unreinforced | Rijckaert et al., 2022 |
Natural Fiber Composites
| Matrix | Fiber | Key Results | Reference |
|---|---|---|---|
| PLA | Flax | 211% flexural strength increase, 224% modulus increase | Zhang et al., 2020 |
| PLA | Carbon/Flax | 430% (carbon) and 325% (flax) tensile strength increase | Kuschmitz et al., 2021 |
| PBS | Hemp | 63% improvement in Young's modulus | Donitz et al., 2023 |
| PP | Hemp | 5% hemp: highest tensile strength; 20% hemp: highest modulus | Sultan et al., 2024 |
| PLA | Basalt | Comparable tensile, superior flexural properties vs PLA/CF | Sang et al., 2019 |
Challenges and Limitations
Reported Limitations in the Literature
| Porosity | Voids and gaps between layers reduce mechanical properties |
| Fiber pull-out | Common failure mechanism indicating poor fiber-matrix adhesion |
| Moisture sensitivity | 9-98% moisture can decrease modulus by 25%, strength by 18% for carbon/PA |
| Discontinuity at fiber start | Fractures occur at fiber deposition start locations |
Modified Mechanisms
3D Compaction Printing (3DCP)
Attaches a hot compaction roller to press printed layers, reducing voids and improving adhesion.
Results:
- 33% tensile strength increase
- 26% flexural modulus increase
- 62% flexural strength increase
Source: Ueda et al., 2020
Modified In-Situ Fusion
Uses an orifice plate to guide continuous glass fiber directly to the melt zone for immediate impregnation and extrusion.
Features:
- Online changing of fiber fraction volume
- Volume fraction range: 35.1% to 49.3%
- Good agreement with theoretical predictions
Source: Akhoundi et al., 2020
Related Topics
3D Printing Materials
Broader overview of materials used in additive manufacturing processes.
Polymer Nanocomposites
Nanoscale reinforcement of polymer matrices for enhanced properties.
Carbon Nanotubes & Fibers
Carbon-based reinforcement materials and their applications.
Natural Fiber Composites
Biodegradable and sustainable fiber reinforcement options.
About This Portal
This portal synthesizes knowledge from "Various FDM Mechanisms Used in the Fabrication of Continuous-Fiber Reinforced Composites: A Review" by Armin Karimi, Davood Rahmatabadi, and Mostafa Baghani, published in Polymers (2024), which reviewed 130 papers in the field.
| Title | Various FDM Mechanisms Used in the Fabrication of Continuous-Fiber Reinforced Composites: A Review |
| Authors | Armin Karimi, Davood Rahmatabadi, Mostafa Baghani |
| Journal | Polymers 2024, 16, 831 |
| DOI | 10.3390/polym16060831 |
| Institutions | University of Tehran; Sharif University of Technology |
Last updated: 2024-12