The Role of Local Interaction Mechanics in Fiber Optic Smart Structures

The concept of using "smart" composite materials/structures with built-in self- diagnostic capabilities for health monitoring involves embedding discrete and/or distributed sensory networks in the host composite material, along with a central and/or distributed artificial intelligence capability for signal processing, data collection, interpretation and diagnostic evaluations. This arti cle concentrates on the sensory functions in "smart" structure applications and concentrates in particular on optical fiber sensors. Specifically, we present an overview of recent research dealing with the basic mechanics of local interactions between the embedded optical fiber sensors and the surrounding host composite. The term "local" is defined by length scales on the order of several op tical fiber diameters. We examine some generic issues, such as the "calibration" and "obtrusivity" of the sensor, and the inherent damage caused by the sensor inclusions to the surrounding host and vice-versa under internal and/or external applied loads. Analytical, numerical and experimental results are presented regarding the influence of local strain concentrations caused by the sensory in clusions on sensor and host performance. The important issues examined are the local mechanistic effects of optical fiber coatings on the behavior of the sensor and the host, and mechanical sur vivability of optical fibers experiencing quasi-static and time-varying thermomechanical loading.