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

Paper Number: 172471

Extrusion-Based Advanced Manufacturing of Thermosetting Polymer Composites 

Advancements in extrusion-based additive manufacturing (AM) have expanded the boundaries of design and fabrication for structural and functional polymer composites. This talk highlights recent progress in direct ink writing (DIW) of thermoset-based short and continuous fiber composites, focusing on the interrelationship between processing, structure, and performance. Compared to thermoplastic AM, thermoset systems offer distinct advantages: superior mechanical strength, enhanced layer-to-layer bonding, improved thermal and chemical resistance, and reduced energy consumption due to room-temperature deposition.

Recent efforts have centered on optimizing ink formulations, tuning rheological behavior, and developing novel curing strategies to achieve high-resolution, mechanically robust printed components. We begin by exploring how filler morphology and loading influence printability and mechanical performance. The effects of key print parameters – such as nozzle diameter and print speed – on filler alignment and mechanical anisotropy are examined in detail. Particular attention is given to the role of fiber length distribution (FLD) in printed short-fiber composites, investigating how FLD governs both the deposition behavior and final mechanical response.

The second segment of the presentation addresses interdiffusion between adjacent roads and printed layers during DIW of thermosetting resins –  a critical factor for mechanical integrity. Using microbeam wide-angle and small-angle X-ray fly-scanning techniques, we achieve micron-scale resolution of structural features within the ink, such as the alignment and distribution of inorganic rheology modifiers. These spatially resolved synchrotron scattering studies reveal a complex interplay of flow-induced nanoparticle alignment and gradient formation, governed by the highly non-equilibrium nature of the DIW process. These results shed light into the often-non-intuitive mechanical performance of 3D printed thermosetting composites and help in the design of next-generation nozzles with optimized geometries.

The third part of the talk introduces a novel reactive extrusion approach that leverages frontal polymerization (FP) for manufacturing continuous fiber-reinforced thermoset composites. FP is a self-sustaining, thermally driven reaction that enables rapid, energy-efficient in-situ curing during deposition. In this process, continuous carbon fiber tows pre-impregnated with dicyclopentadiene (DCPD) are compacted and cured using localized heat and pressure from a pair of rollers. We examine the effects of extrusion speed, roller temperature, and compaction force on fiber volume fraction and mechanical properties. The resulting CFRP structures exhibit elastic moduli comparable to conventionally cured tows, with extrusion rates up to 5 mm/s, enabling mold-free, freestanding shape formation. Notably, the fabricated composites achieve up to 95% of the theoretical longitudinal elastic modulus. A homogenized thermo-chemical model further elucidates the impact of process parameters on reaction kinetics and energy efficiency.

Overall, this integrated manufacturing framework offers significant advantages in curing speed, energy consumption, tooling simplicity, and part performance – paving the way for scalable, sustainable production of high-performance thermoset composites.

Presenting Author: Nadim Hmeidat Oak Ridge National Laboratory (ORNL)

Presenting Author Biography: Nadim Hmeidat is a Research Scientist in advanced manufacturing at the Manufacturing Demonstration Facility (MDF) at Oak Ridge National Laboratory (ORNL). He earned his Ph.D. in Mechanical Engineering from the University of Tennessee, Knoxville (UTK), specializing in additive manufacturing (AM) of thermoset polymer composites. Before joining ORNL, he was a Postdoctoral Research Associate at the Beckman Institute for Advanced Science and Technology at the University of Illinois Urbana-Champaign (UIUC), where he developed a novel extrusion process for rapid and energy-efficient manufacturing of continuous fiber thermoset composites using self-energized frontal polymerization. Dr. Hmeidat has authored over 20 peer-reviewed articles in leading scientific journals and has received numerous awards, including the SAMPE 2024 Young Professional Emerging Leadership Award, the 2023 American Society for Composites (ASC) Best Paper Award, the Center for Materials Processing (CMP) Fellowship, and the UTF Dr. Hui Ph Memorial Scholarship at UTK.

Authors:

Nadim Hmeidat Oak Ridge National Laboratory (ORNL)