Rapid de-stiffening of multilayer transparent structures using controlled thermoplastic softening
Rapid de-stiffening of multilayer transparent structures using controlled thermoplastic softening
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DOI：
10.1088/1361-665x/acff52
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发表时间：
2023-10
影响因子：
4.1
通讯作者：
Dimitrios Charaklias;D. Qiang;Robert Dorey;Iman Mohagheghian
中科院分区：
文献类型：
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作者：
Dimitrios Charaklias;D. Qiang;Robert Dorey;Iman Mohagheghian
热塑性软化是最理想的去刚化方法之一，因为其可逆性、可扩展性和在许多当前多层结构中的适用性而不损害结构性能。尽管有这些优点，但长激活时间和高激活功率要求通常被认为是该方法的主要缺点，这可能会限制其在需要快速去硬化的情况下的应用。本研究的目的是确定加热元件的关键设计要求，以最大限度地减少使用热塑性软化的去硬化响应时间，同时最大限度地提高透明度。本研究的重点是多层透明结构，具有低发热元件含量。系统的调查，包括实验和数值研究，进行研究的填充因子和加热元件的长度尺度上的响应时间的去刚化的效果。聚合物的熔化和加热元件的熔化或电击穿被观察为实际限制，并且被引入作为对设计图的约束。发现填充因子对改善响应时间具有相当大的影响，特别是在低填充因子（即低于10%）下。对于本文研究的材料组合，设计图显示，导线直径最大为7 μm，最大透明度为2%填充因子，最大透明度为12 μm，最大透明度为20%填充因子的加热元件，可以在温度升高30 °C时实现亚秒级响应时间。这种新的理解将加速主动结构控制技术的技术成熟水平，用于未来的多功能和智能结构，在机器人，形状变形，主动阻尼和主动冲击保护方面具有广泛的应用。
Thermoplastic softening is one of the most desirable de-stiffening methods because of its reversibility, scalability, and applicability in many of current multi-layered structures without compromising structural performance. Despite the advantages, long activation times and high activation power requirements are generally considered as the main drawbacks for this method which can potentially limit its application in scenarios where fast de-stiffening is required. The aim of this study is to identify the key design requirements of heating element to minimise the de-stiffening response time using thermoplastic softening while maximising transparency. The focus of this study is on multilayer transparent structures, with low heating element content. A systematic investigation, including experimental and numerical investigation, is performed to study the effect of the fill factor and the heating element’s length scale on the response time of de-stiffening. Melting of the polymer and melting or electrical breakdown of the heating element are observed as practical limitations and are introduced as constraints to the design maps. The fill factor is found to have considerable influence on improving the response time, especially at low fill factors (i.e. below 10%). For the material combinations investigated here, the design maps show that heating elements with wire diameters up to 7 μm, at maximum transparency of 2% fill factor and up to 12 μm at 20% fill factor can achieve sub-second response times for temperature increase of 30 °C. This new understanding will accelerate the technology readiness level of active structural control technology to be used in the future multi-functional and smart structures with a wide range of application in robotics, shape morphing, active damping, and active impact protection.