Session: 16-01-07: Polymers and Composites II

Paper Number: 166797

Enhancing FDM 3D Printed Polymers via Low-Cost Continuous Fiber Reinforcement 

Additive manufacturing via fused deposition modeling (FDM) has transformed rapid prototyping and the fabrication of complex geometries. However, its reliance on polymer materials often resulted in limited mechanical strength and significant anisotropy. While commercial solutions, such as the Markforged Mark Two, demonstrated that continuous fiber reinforcement could dramatically enhance mechanical performance, their high cost and limitations in fiber reinforcement hindered widespread adoption.

This study investigated a low-cost alternative by integrating continuous fiber reinforcement into standard PLA-based FDM prints through a post-processing method. This approach involved inserting fibers—maintaining a constant tow—into pre-designed reinforcement channels and infusing epoxy to secure them. A comparative analysis was conducted between unreinforced PLA specimens and fiber-reinforced counterparts, systematically varying key parameters such as fiber volume fraction and orientation.

Mechanical characterization followed ASTM-D3039 for tensile testing and ASTM-E2769 for three-point bending of complex truss structures to evaluate enhancements in tensile strength, Young’s modulus, and flexural properties. This investigation demonstrated that a low-cost, post-processing fiber reinforcement technique significantly improved the structural performance of FDM-printed parts, broadening their applicability in engineering contexts that demand both intricate geometries and enhanced mechanical properties.

The research focused on reinforcing 3D-printed parts produced on an Ender 3 FDM 3D printer by pulling carbon fiber through channels designed into the part. To prepare the specimen, a model of the desired test geometry was created in Autodesk Inventor. Using the sweep command, circular channels were cut through the length of the part. The model was then exported and sliced for printing on a consumer FDM 3D printer using PLA filament, chosen for its well-known 3D printing properties and widespread use. Upon removal from the printer, continuous carbon fiber coated in epoxy was fed through the channels, with additional epoxy injected via a syringe to minimize voids. Excess fiber was trimmed, and the part was left to fully cure.

Tensile testing was conducted on 36 ASTM D-638 specimens to evaluate various material properties. The first evaluation included 12 PLA tensile specimens with no reinforcement, printed at three different orientations (three specimens per orientation). The second analysis involved 12 PLA specimens with fiber-reinforced channels, tested at three print orientations with a fixed fiber volume fraction. The final tests were conducted on 12 specimens at varying fiber volume fractions and three print orientations. For these tests, ultimate tensile strength, Young’s modulus, Poisson’s ratio, and elongation were evaluated. The results of different fiber matrix volume specimens were compared based on ultimate tensile strength, and stress-strain curves were used for further analysis. The rule of mixtures was applied to predict strength outcomes and compare them to experimental values, with percentage improvements reported for each configuration.

Complex geometry testing was performed using a three-point bending test, where PLA truss structures were compared to their fiber-reinforced counterparts. Three specimens were tested per bending configuration—three non-reinforced and three reinforced—to evaluate flexural properties. This test demonstrated a significant percentage difference in strength between the reinforced and non-reinforced samples, validating the effectiveness of the proposed reinforcement method.

Presenting Author: Seyed Hamid Reza Sanei Pennsylvania State University

Presenting Author Biography: Dr. Sanei is an associate Professor of mechanical engineering at Pennsylvania State University. Dr. Sanei's research is in the area of additive manufacturing of polymers and composites.

Authors:

Andrew Prouty Pennsylvania State University
Adam Sacherich Pennsylvania State University
Sean Schneider srs6292@psu.edu Pennsylvania State University
Seyed Hamid Reza Sanei Pennsylvania State University