Fibre-reinforced, fluid-filled structures are commonly found in nature and emulated in devices. Researchers in the field of soft robotics have used such structures to build lightweight, impact-resistant and safe robots. The polymers and biological materials in many soft actuators have these advantageous characteristics because of viscoelastic energy dissipation. Yet, the gross effects of these underlying viscoelastic properties have not been studied. We explore nonlinear viscoelasticity in soft, pressurized fibre-reinforced tubes, which are a popular type of soft actuation and a common biological architecture. Relative properties of the reinforcement and matrix materials lead to a rich parameter space connecting actuator inputs, loading response and energy dissipation. We solve a mechanical problem in which both the fibre and the matrix are nonlinearly viscoelastic, and the tube deforms into component materials’ nonlinear response regimes. We show that stress relaxation of an actuator can cause the relationship between the working fluid input and the output force to reverse over time compared to the equivalent, non-dissipative case. We further show that differences in design parameter and viscoelastic material properties can affect energy dissipation throughout the use cycle. This approach bridges the gap between viscoelastic behaviour of fibre-reinforced materials and time-dependent soft robot actuation.

中文翻译：

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通过组件材料的非线性粘弹性实现复合管中的力反转和能量耗散


纤维增强、充满液体的结构在自然界中很常见，并在设备中被模拟。软体机器人领域的研究人员已经利用这种结构来建造轻质、耐冲击且安全的机器人。由于粘弹性能量耗散，许多软致动器中的聚合物和生物材料具有这些有利的特性。然而，这些潜在粘弹性特性的总体影响尚未得到研究。我们探索柔软的加压纤维增强管中的非线性粘弹性，这是一种流行的软驱动类型和常见的生物结构。增强材料和基体材料的相对特性导致连接致动器输入、负载响应和能量耗散的丰富参数空间。我们解决了一个机械问题，其中纤维和基体都是非线性粘弹性的，并且管变形为组件材料的非线性响应状态。我们表明，与等效的非耗散情况相比，执行器的应力松弛会导致工作流体输入和输出力之间的关系随着时间的推移而发生逆转。我们进一步表明，设计参数和粘弹性材料特性的差异会影响整个使用周期的能量耗散。这种方法弥补了纤维增强材料的粘弹性行为与时间相关的软机器人驱动之间的差距。