Characterization of Mechanical Properties in Multifunctional Structural-Energy Storage Nanocomposites for Lightweight Micro Autonomous Systems

A major concern in the design of micro-robotic systems is an on-board energy supply capable of providing the necessary power requirements, while limiting the volume/mass burden to the vehicle. The conventional solution to this design problem is to maximize the energy density of the on-board power supply. An alternative approach is to replace single-function structural components with multifunctional structural-energy storage materials. The mass and volume savings associated with the material substitution could potentially result in improved endurance and/or increased payload (e.g. video camera, microphone, chemical/biological sensors). In this study, carbon nanotube (CNT) based composites were used to fabricate structural-energy storage materials. Specifically, supercapacitor electrodes were constructed from paper covered with CNT ink and from polymer matrices infused with aligned CNT forests. The composites were subject to bulk mechanical tests in order to characterize their suitability as structural components in micro-autonomous systems. Tensile tests on the paper composites show directional and strain rate dependencies. The CNT-ink deposition process was found to degrade the elastic modulus of the paper by approximately 50%, although the tensile strength of the materials was largely unaffected. Preliminary electrical characterization of the CNT-coated electrode materials indicate that the nanomaterials potentially reach a percolation threshold after multiple depositions, resulting in a conductive surface network. Initial results indicate that improvements in the electrical properties of the CNT paper electrodes are met with reductions in the mechanical performance of the composites.