Session: Rising Stars of Mechanical Engineering Celebration & Showcase

Paper Number: 148049

148049 - 3d/4d Printing of Multifunctional Active Composites With Dynamic Molecular Bonding 

3D printing of continuous fiber composites has opened exciting possibilities for rapid prototyping and composite product development. Our recent research focuses on integrating active polymers with dynamic molecular bonding into the printing processes. For instance, we utilize the newly emerged two-stage UV curable resin during 3D printing. Following the printing process, the composite samples undergo post-heating treatment. The thermally triggered bond exchange reactions (BERs) induce a second-stage polymerization, resulting in an approximately 11-fold increase in the matrix modulus, alongside uniform curing, and robust bonding among adjacent filaments. Remarkably, our printed composites demonstrate a notable 103% enhancement in filament bonding strength and an 11-fold increase in three-point bending strength. Moreover, BERs offer unique advantages of repairability, reshapability, and recyclability to the printed samples, significantly enhancing the durability, reliability, and sustainability of composite products. Additionally, we incorporate liquid crystal elastomer (LCE) resin during the composite 3D printing. During the printing process, the relative motion between the continuous fiber and LCE resin generates shear force to align mesogens and enable the monodomain state of the matrix. The asymmetric positioning of embedded fibers allows the printed composite lamina to exhibit highly tunable reversible folding deformations. The composite also demonstrates high actuation forces, exceptional energy absorption, and protection capabilities. Various shape-changing patterns of 4D composites can be achieved by adjusting the printing pathway. Furthermore, the incorporation of conductive fiber into the LCE matrix enables electrically induced shape morphing in printed composites. Overall, integrating active polymers with composite 3D printing holds significant potential in addressing major challenges in the field and substantially expanding the multifunctionality and application scopes of printed composites. Our research has received funding from the 2021 NSF CAREER award.

Presenting Author: Kai Yu University of Colorado Denver

Presenting Author Biography: Dr. Kai Yu currently is an Associate Professor in the Department of Mechanical Engineering at the University of Colorado Denver. He earned his Ph.D. in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. Prior to that, he studied at the University of Colorado Boulder and received his Bachelor’s degree in Engineering Mechanics from Harbin Institute of Technology (China). Dr. Yu's research focuses on the mechanics of polymers, composites, and the design of their applications using 3D printing. Specifically, he is interested in understanding and modeling the evolution of material structures and mechanical properties under various processing conditions or environmental stimuli. The objective is to integrate with finite elements computational tools to solve complex 3D multi-physics problems involving nonlinear mechanics. His studies also guide the development of innovative 3D printing techniques for polymers and composites with extended applications.

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