Session: 03-01-03: Annual Conference-Wide Symposium on Additive Manufacturing

Paper Number: 150527

150527 - Embedded 3d Printing of Uv-Curable Thermosetting Composites With Continuous Fiber 

3D printing, also known as additive manufacturing, offers significant advantages for composite manufacturing. It provides exceptional design flexibility while eliminating the need for molds to shape the resin and fiber. Extrusion-based 3D printing methods with in-nozzle impregnation mechanisms have been extensively employed in fabricating composites with continuous fiber, for example direct ink writing (DIW) continuous fiber printing technique. Despite exciting developments in the field, several grand challenges persist, which cannot be addressed by simply optimizing existing printing processes. Firstly, following filament deposition, the matrix resin spreads, and the embedded fiber bundle tends to loosen or misalign. While intense UV light facilitates the rapid fixation of the resin and fiber, it leads to noticeable void formation among filaments due to their cylindrical geometry and weak inter-filament bonding strength. These phenomena ultimately compromise the mechanical performance of printed composites. Secondly, all current printing processes for UV-curable composites share a similar nozzle impregnation mechanism. The ability to dynamically adjust the fiber volume fraction or change the matrix materials in situ during the printing process is restricted unless a separate nozzle with a distinct diameter is employed. These limitations significantly constrain design flexibility and manufacturing capabilities for contemporary composites with highly optimized distributions of continuous fiber and matrix materials. Thirdly, while existing studies demonstrate the successful printing of free-standing structures, the printing of composite structures with larger-scale hollow features poses a considerable challenge. Gravitational forces would continuously deform the deposited filaments in the absence of support materials.

 

This study presents an innovative embedded 3D printing technique that addresses significant challenges associated with existing methods. The technique utilizes a deposition nozzle to precisely write continuous fibers below the resin. A laser beam is directed onto the resin surface, which simultaneously cures the resin around the fiber bundle. It can print with or without substrate. The printing method demonstrates its advantages in producing high-quality composite samples with well-aligned fibers, minimized void density, great bonding between filaments, and outstanding mechanical properties. The longitudinal and transverse moduli of printed lamina with different fiber content match the rule of mixtures. More importantly, it introduces several capabilities that are highly desirable in the fabrication of contemporary composites, yet unattainable with existing methods, including the dynamic control of fiber volume fractions and the ability to change matrix materials during printing. Furthermore, it enables the printing of overhanging filaments for hollow features without the need of support materials. The developed printing method exhibits versatility in working with different commercially available feedstock resins and reinforcement fibers. It is anticipated to be an impactful approach for future development of thermosetting composites with diverse structural or multi-functional applications.

Presenting Author: Yuchen Ding University of Colorado Denver

Presenting Author Biography: Yuchen Ding is a PhD candidate at University of Colorado Denver. Yuchen completed his master's degree at UCLA and his undergraduate studies at University of Liverpool. His research focuses on promoting bonding strength of dissimilar materials and continuous fiber 3D printing.

Authors:

Yuchen Ding University of Colorado Denver
Alston Gracego University of Colorado Denver
Yuanrui Wang University of Colorado Denver
Guoying Dong University of Colorado Denver
Martin Dunn University of Colorado Denver
Kai Yu University of Colorado Denver