Abstract
In constant pursuit of lightweight, efficient, and resilient structures, the focus to Multi-Functional Structure (MSF) has increasing grown over the past decade. The MFSs combine load-bearing capacity with other functionalities such as thermal/electrical conductivity or insulation, electromagnetic shielding, energy storage, self-healing, stiffness modulation, or any combination of them. In constant pursuit of lightweight, efficient, and resilient structures, attention to Multi-Functional Structure (MSF) has increasing grown over the last decade. The MFSs often combine load-bearing capacity with other functionalities such as thermal/electrical conductivity or insulation, electromagnetic shielding, energy storage, self-healing, stiffness modulation, or any combination of them. Often constituted of hybrid materials, MFSs employ stimuli-responsive materials, allowing them to adapt to external factors like heat, pressure, electrical current, magnetic or electrical fields, moisture, pH levels, or light. Amongst various methods, thermal softening in thermoplastics 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. However, the reliance on delivering thermal energy introduces challenges such as prolonged activation times and high-power requirements, limiting its application in scenarios requiring rapid de-stiffening, such as impact protection. This paper systematically investigates the parameters influencing the response time of de-stiffening, focusing on characteristics such as the size of the heating element and the volume, as well as the thermal properties of the material to be heated. We employed three types of heating elements embedded in multi-layered structures, namely wires, structured metallic meshes, and random metallic meshes (refer to Figure 1). Our findings demonstrate that achieving a very fast heating rate (45°C·s-1) is feasible using random metallic meshes under 4.8 V excitation. Figure 1: Embedding various types of heating element in multi-layered structures.