3D printing allows for moldless fabrication of continuous fiber composites with high design freedom and low manufacturing cost per part, which makes it particularly well-suited for rapid prototyping and composite product development. Compared to thermal-curable resins, UV-curable resins enable the 3D printing of composites with high fiber content and faster manufacturing speeds. However, the printed composites exhibit low mechanical strength and weak interfacial bonding for high-performance engineering applications. In addition, they are typically not reprocessable or repairable; if they could be, it would dramatically benefit the rapid prototyping of composite products with improved durability, reliability, cost savings, and streamlined workflow. In this study, we demonstrate that the recently emerged two-stage UV-curable resin is an ideal material candidate to tackle these grand challenges in 3D printing of thermoset composites with continuous carbon fiber. The resin consists primarily of acrylate monomers and crosslinkers with exchangeable covalent bonds. During the printing process, composite filaments containing up to 30.9% carbon fiber can be rapidly deposited and solidified through UV irradiation. After printing, the printed composites are subjected to post-heating. Their mechanical stiffness, strength, and inter-filament bonding are significantly enhanced due to the bond exchange reactions within the thermoset matrix. Furthermore, the utilization of the two-stage curable resin enables the repair, reshaping, and recycling of 3D printed thermosetting composites. This study represents the first detailed study to explore the benefits of using two-stage UV curable resins for composite printing. The fundamental understanding could potentially be extended to other types of two-stage curable resins with different molecular mechanisms.
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Thermoset composite recycling – Driving forces, development, and evolution of new opportunities
Thermoset composites represent a substantial challenge for recycling, even as composite products increase in market interest. The concept of putting all future thermoset composite products into landfills over the next decades is unlikely to continue. This paper examines the three eras in the history of thermoset product recycling, the drivers for increased recycling, and possible future trends. Technology for managing thermoset composite products at end-of-life first focused on retrieving fiber and to a lesser extent resin. Then in a second era, research focused on better utilization of recovered fiber and finally the third era is now keeping more of the original resin–fiber structure to reuse these composites. Drivers are emerging to stimulate thermoset recycling, including States with success in recycling other challenging products (tires, carpets, automobile parts, etc.) setting policy and fees to encourage recycling. The evolution of heat recovery as a thermoset recycling option in Europe is another driver. Additionally, efforts at certification of recycled fiber quality may stimulate greater reuse.
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- Award ID(s):
- 1743682
- NSF-PAR ID:
- 10213561
- Date Published:
- Journal Name:
- Journal of Composite Materials
- Volume:
- 52
- Issue:
- 8
- ISSN:
- 0021-9983
- Page Range / eLocation ID:
- 1033 to 1043
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1177/0021998317720000
