The mechanical behaviour of isotropic-genesis, polydomain liquid crystal elastomers (I-PLCEs) at various strain rates is systematically investigated via experiments, theoretical analysis, and numerical modelling. Experiments encompassing SEM (scanning electron microscope), DSC (differential scanning calorimetry), TGA (thermogravimetric analyser), quasi-static and dynamic (SHPB – split Hopkinson pressure bar) mechanical tests, as well as drop-weight impact tests, are undertaken to identify the nonlinear, large-strain, rate-dependent relationship between compressive stress and deformation of the I-PLCEs studied. Subsequently, a three-dimensional compressible visco-hyperelastic constitutive model for the material is established based on the summation of Cauchy stress components. The as-used model yields good agreement with experimental data, particularly an excellent description of the mechanical responses at high strain rates of 103∼104 s−1. The fully-calibrated constitutive model is implemented in the commercial finite element code ABAQUS via a virtual user-defined material (VUMAT) subroutine. The inhomogeneous deformation processes of the I-PLCEs, corresponding to impact by a hemispherically-tipped drop weight, which induces complex stress states, are also well described. Finally, when evaluated by two dimensionless physical parameters, the I-PLCEs demonstrate a more pronounced strain rate sensitivity in terms of dynamic strength and impact toughness compared to other commonly used materials, highlighting their superior performance in dynamic loading scenarios. The present study is helpful for the design and development of impact-resistant LCE-based materials and structures.

中文翻译：

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高应变速率下各向同性成因、多域液晶弹性体的非线性力学行为和粘超弹性本构描述


通过实验、理论分析和数值建模，系统研究了各向同性成因、多域液晶弹性体 （I-PLCEs） 在不同应变速率下的机械行为。进行了包括 SEM（扫描电子显微镜）、DSC（差示扫描量热法）、TGA（热重分析仪）、准静态和动态（SHPB – 分体式霍普金森压力棒）机械测试以及落锤冲击测试在内的实验，以确定所研究的 I-PLCE 的压应力和变形之间的非线性、大应变、速率依赖性关系。随后，基于柯西应力分量的总和建立了该材料的三维可压缩粘超弹性本构模型。现有模型与实验数据具有良好的一致性，特别是对 103∼104 s-1 高应变速率下的机械响应的出色描述。完全校准的本构模型通过虚拟用户定义材料 （VUMAT） 子程序在商业有限元代码 ABAQUS 中实现。I-PLCE 的非均匀变形过程，对应于半球形落锤的冲击，这会导致复杂的应力状态，也得到了很好的描述。最后，当通过两个无量纲物理参数进行评估时，与其他常用材料相比，I-PLCE 在动态强度和冲击韧性方面表现出更明显的应变速率敏感性，突出了它们在动态载荷场景中的卓越性能。本研究有助于设计和开发抗冲击的 LCE 基材料和结构。