SIM-AM 2023

Thermomechanical Behavior of 3D-printed Liquid Crystal Elastomer

  • Chen, Yuzhen (Fudan University)
  • Li, Wenxuan (Fudan University)
  • Zhao, Songshan (Fudan University)
  • Huo, Yongzhong (Fudan University)

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Liquid crystal elastomers (LCEs) are soft materials capable of large, reversible deformations in response to external stimuli such as temperature, light or electric fields. Due to the coupling between the polymer network deformation and the rotation of the mesogens, LCEs exhibit very unique and intriguing thermomechanical behaviors. Recently, additive manufacturing (AM) techniques for LCEs have been largely explored, and have enabled complex geometries and various patterns of mesogen alignment, leading to a wide range of applications in artificial muscles, soft robots and morphing medical devices. Particularly, the direct ink writing (DIW), which is an extrusion-based AM technique, can print complex three-dimensional LCE structures and align the mesogens along the print path by imposing shear forces. Herein, we investigate the influence of printing parameters on the thermomechanical properties of the 3D-printed LCEs. We examine the stress-strain curves of uniaxially-stretched LCE sheets with the loading direction perpendicular to the mesogen alignment direction, and observe semi-soft elasticity featuring stress plateaus when the testing temperature is below the nematic-to-isotropic transition temperature. Based on the stress-strain curves, we calculate relevant material parameters at different testing temperatures, and find great dependency on the printing parameters. With these material parameters, our numerical model can predict the stress-strain relations for LCEs with other mesogen alignment directions. Our work established a connection between the 3D printing process and the material properties, which provides assistance in developing LCE-based morphing and actuating structures.