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Abstract This review highlights recent progress in additive manufacturing (AM) techniques for polymer composites reinforced with nanoparticles, short fibers, and continuous fibers. It also explores the integration of functional resins and fibers to enable advanced capabilities such as shape morphing, enhanced electrical and thermal conductivity, and self-healing behavior. Building on these advances, the review examines computational design strategies that optimize material distribution and fiber orientation. Representative approaches range from density-based methods to emerging level-set topology optimization frameworks, with objectives evolving from improving mechanical performance to addressing complex multi-physics functional requirements. The review also identifies emerging opportunities, including the need for technological innovations to further improve mechanical properties and enable adaptable multifunctionality. Further advances in theoretical modeling and integrated design-printing workflows are also discussed. By synthesizing these developments, this review aims to foster interdisciplinary collaborations and accelerate innovation in AM-enabled composite materials across a wide range of applications. 

Abstract Within the past two decades, covalent adaptable networks (CANs) have emerged as a novel class of dynamically crosslinked polymers, combining the benefits of thermosets and thermoplastics. Although some CANs with charged side chains have been reported, CANs with negatively charged backbones remain very limited. The integration of permanent charge into the backbones upon their formation could open up important new applications. Here, we introduce a series of aliphatic spiroborate‐linked ionic covalent adaptable networks (ICANs), representing a new category of dynamic ionomer thermosets. These ICANs were synthesized using a catalyst‐free, scalable, and environment‐friendly method. Incorporating lithium or sodium as counter cations in these networks yielded promising ion conductivity without the need of plasticizers. The dynamic nature of the spiroborate linkages in these materials allows for rapid reprocessing and recycling under moderate conditions. Furthermore, their potential as flexible solid‐state electrolytes is demonstrated in a device that maintained robust conducting performance under extreme physical deformation, coupled with effective self‐healing properties. This research opens new possibilities for future development of dynamic ionomer thermosets and their potential applications in flexible electronic devices. 

Abstract Liquid crystal elastomers (LCEs) exhibit unique mechanical properties of soft elasticity and reversible shape‐changing behaviors, and so serve as potentially transformative materials for various protective and actuation applications. This study contributes to filling a critical knowledge gap in the field by investigating the microscale mesogen organization of nematic LCEs with diverse macroscopic deformation. A polarized Fourier transform infrared light spectroscopy (FTIR) tester is utilized to examine the mesogen organizations, including both the nematic director and mesogen order parameter. Three types of material deformation are analyzed: uniaxial tension, simple shear, and bi‐axial tension, which are all commonly encountered in practical designs of LCEs. By integrating customized loading fixtures into the FTIR tester, mesogen organizations are examined across varying magnitudes of strain levels for each deformation mode. Their relationships with macroscopic stress responses are revealed and compared with predictions from existing theories. Furthermore, this study reveals unique features of mesogen organizations that have not been previously reported, such as simultaneous evolutions of the mesogen order parameter and nematic director in simple shear and bi‐axial loading conditions. Overall, the findings presented in this study offer significant new insights for future rational designs, modeling, and applications of LCE materials. 

Abstract Soft-elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications where strain energy is ideally absorbed at constant stress. Conventionally, compressive and impact studies on LCEs have not been performed given the notorious difficulty synthesizing sufficiently large monodomain devices. Here, we use direct-ink writing 3D printing to fabricate bulk (>cm 3 ) monodomain LCE devices and study their compressive soft-elasticity over 8 decades of strain rate. At quasi-static rates, the monodomain soft-elastic LCE dissipated 45% of strain energy while comparator materials dissipated less than 20%. At strain rates up to 3000 s −1 , our soft-elastic monodomain LCE consistently performed closest to an ideal-impact absorber. Drop testing reveals soft-elasticity as a likely mechanism for effectively reducing the severity of impacts – with soft elastic LCEs offering a Gadd Severity Index 40% lower than a comparable isotropic elastomer. Lastly, we demonstrate tailoring deformation and buckling behavior in monodomain LCEs via the printed director orientation.