Embedded Fiber Optic Sensors for Integral Armor

摘要

This report describes the work performed with Production Products Manufacturing & Sales (PPMS), Inc., under the 'Liquid Molded Composite Armor Smart Structures Using Embedded Sensors' Small Business Innovative Research (SBlR) Program sponsored by the U.S. Army Research Laboratory (ARL). In the Phase I effort, fiber optic sensor systems were investigated for in-process cure monitoring and in-service health and dynamic response monitoring of monocoque and hybrid liquid molded composite armor structural parts. Sensor embedding techniques during resin infusion molding were developed, thick panels with varying residual stress characteristics were fabricated, two fiber optic sensor types were utilized and compared, several demodulation techniques were studied, and information processing programs were written for converting the sensor signal to engineering data. Bragg grating and fluorescence optrode fiber optic sensors were selected and embedded in armor panels to monitor the cure of the systems and health of the panels during impact and four-point bend tests. During panel curing, the Bragg gratings detected the change in strain in the material at the onset of cross-linking as well as the strain changes (residual stress) resulting from panel processing. The Bragg gratings, serving a dual purpose, measured the resulting strain from the external loads applied due to impact and bending. The fluorescence optrode was used during the cure process only to measure the changes in the material as it cured (degree of cure). Stitching of thick-section fiberglass preforms was also investigated.