The Study of SMAT Based Multistable Nanomaterials for Wing Morphing and Energy Harvesting

基於SMAT技術的多穩態納米材料在機翼變形和能量收集中的研究

Student thesis: Doctoral Thesis

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Award date29 Jul 2020

Abstract

Multistable materials have attracted people’s eye for a long time due to their morphing abilities which have excellent application foreground in both energy conservation and generation fields. So far, the multistable materials are mainly explored for wing morphing to reduce the energy expenditure of aircraft, and for energy harvesting to broaden new sources of energy. Compared with the most commonly used bistable composite laminates, the surface mechanical attrition treatment (SMAT) based multistable nanomaterials have more advantages in the above two applications. Firstly, the multistable nanomaterials have a higher load capacity than the bistable composite laminates due to the nanometer effect caused by SMAT processing. Secondly, different from the monolithic deformation mechanism of the bistable composite laminates, the multistable nanomaterials are locally deformed. The local bistable regions can be arbitrarily designed on a metallic plate. Besides, the local bistability is beneficial to design different forms of multistable nanomaterials. Thirdly, the multistable nanomaterials can offer more morphing abilities and nonlinear characters which are crucial for the applications of wing morphing and energy harvesting. Based on these two potential applications of the multistable nanomaterials, this dissertation is divided into two parts: multistable morphing trailing-edge wing for energy conservation and bistable vibration energy harvester for energy collection.

In the first part of this dissertation, a continuous morphing trailing-edge wing (CMW) concept based on the novel multistable nanomaterial is proposed and numerically studied. It is generally known that the morphing technology has been one of the most effective methods to improve the aerodynamic performance of aircraft. Traditional morphing methods based on control surfaces are mature and widely used on current civil and military aircraft, but insufficiently effective for the entire flight envelope. Recent research on morphing wing still faces the challenge that the skin materials for morphing should be both deformable and stiff. In this dissertation, the multistable nanomaterial-based CMW is designed and fabricated. The computational fluid dynamics (CFD) method is adopted to study the aerodynamic performance of the CMW. Results show that the CMW can effectively reduce drag during the morphing process and has a better aerodynamic performance than the traditional flap morphing wing (FMW).

The second part of this dissertation is about energy harvesting research using bistable nanomaterial. It is well known that one of the critical drawbacks of the linear vibrational energy harvesting devices is that their optimum performances are only effective around their fundamental resonance frequencies. This narrow-band feature restricts the application of these linear devices in a real environment where the vibration sources always have a wide frequency spectrum. Therefore, to solve this problem, a novel concept of nonlinear broadband vibration energy harvester fabricated with a new bistable nanomaterial is proposed. Numerical simulations and experimental tests are conducted to explore its energy harvesting performance and intrinsic nonlinear vibration characteristics. Both the results from simulation and experiments prove that this nonlinear nanomaterial-based bistable energy harvester (NBEH) is far superior to the linear resonant harvesters.

It seems that these two works are independent but are all related. It is because they all rely on the morphing ability of the multistable nanomaterials, and also have a common goal for contributing to the energy issue. Therefore, some research details of these two works are crossed and referred to in this dissertation. The results of these two works prove that the SMAT based multistable nanomaterials can play a positive effect on both morphing wings for energy conservation and bistable harvesters for energy conversion. Besides, they all show great potential for future practical applications.

    Research areas

  • multistable nanomaterials, SMAT, morphing wing, energy harvesting, CFD, nonlinear vibration