The mechanical state of structures need to be monitored for a variety of reasons, including health diagnostics and health prognostics. The task of identifying the location and nature of damage initiation and growth is made difficult by limitations of (i) sensor technologies and (ii) sensor densities; that can be achieved in realistic structures. Current technologies for mechanical sensors mostly focus on measuring deformations or stains, and are thus useful for deformation-based failure prediction models. In this study we propose to develop a novel class of MEMS-based, self-sufficient sensors that will make direct in-situ measurements of instantaneous local strain, stress, stiffness and energy density in the host structure. Specifically, we have proposed to: (a) provide proof-of-concept of the basic principles for a novel and completely new stiffness/energy sensor; (b) demonstrate a MEMS implementation of the underlying principles; and (c) demonstrate its application for damage/degradation modeling by mounting it externally to structural coupons. It is anticipated that this study will demonstrate and deliver the first working version of a fully autonomous sensor that will provide real-time, in-situ measurements of the changes in a structure's local stiffness and strain energy density. In conjunction with the damage models to be developed during this study, this sensor will provide the first real opportunity to perform real-time health prognostics in complex structures, experiencing complex dynamic loading throughout their life-cycle.
