Design and Analysis of a Bracing Bistable Compliant Mechanism with Structural Health Monitoring Capabilities

Abstract

Compliant mechanisms utilize elastic bending to deform in a predictable manner, whileoffering advantages such as monolithic construction, high motion precision, and zero back- lash compared to traditional rigid-body mechanisms. These advantages offer a significant impact in the aerospace industry, where cost, weight, maintainability, and complexity are significant bounding variables. This thesis presents the design and analysis of a bi-stable compliant mechanism utilizing beam bracing to achieve beam snap-through while a critical strain is exceeded. Parametric equations for the response of this mechanism are derived using pseudo-rigid body models (PRBMs) and potential energy to enable efficient iterations on initial designs and to inform parameter tuning for desired behaviors. These parametric equations provide an efficient alternative to more computationally expensive finite element methods, especially with regard to initial mechanism design. A potential application of the proposed compliant mechanism is in aerospace structural health monitoring (SHM). Integrating the bi-stable mechanism response as a function of specified strain threshold offers both a passive and active indicator of excessive loading or possible damage progression in principal structural elements (PSE). Experimental valida- tion and numerical simulations in ANSYS demonstrate the feasibility of the mechanism as an SHM sensor. This study contributes to the broader field of compliant mechanisms by providing a design and analysis methodology for a bracing-triggered bi-stable system that is activated by strain exceedance. This research also highlights the potential applications for compliant mechanisms in aerospace structural monitoring in both passive and active systems as a possible complementary addition to conventional sensors.