Optical Fiber Sensor Research at NCSU
October 1, 2005
By Dr. N Ma, NCSU
Optical fiber sensors can measure a multitude of parameters including strain, temperature, humidity, and acoustic waves. Due to their robustness, small size, immunity to electromagnetic interference and multiplexing capabilities they have been deployed in a large number of structures including aircraft, spacecraft, bridges, and buildings. Professor Peters' research is focused on their implementation in composite laminate material systems. A significant component of this research involves modeling the opto-mechanical response of the sensors due to changes in the surrounding host material system. Currently, Professor Peters is collaborating with Professor Zikry who has internationally recognized expertise in the three-dimensional, computational modeling of such heterogeneous material systems. The goal of this work is the development of an integrated experimental, analytical, and computational and investigation of material deformation, damage, and failure modes for woven composite laminates during low velocity impacts. These efforts will provide for better optimization of these materials and accurate prediction of their failure behavior based on evolving physical mechanisms.
 Specifically, Professors Peters' and Zikry's graduate students are investigating the measurement of strain throughout the impact loading cycle in order to understand the interaction between multiple occurring failure modes. Concurrently, they have developed techniques to separate sensor failure from the composite material based on multiple lightwave modes propagated through the sensor. The measurement of local damage parameters implies that the sensors closest to the localized damage, those which provide the most information about the damage parameters, are necessarily the sensors most susceptible to failure. Thus, in many applications, strictly filtering of the sensor data is not a suitable solution to treating sensor failures.
Professor Peters' group also is developing polymer optical fiber (POF) sensors for high strain applications such as morphing aircraft and earthquake damaged structures (in collaboration with Professors Hassan and Kowalsky in the Civil Engineering department at NCSU). POF sensors have been used considerably for chemical and environmental monitoring due to the high sensitivity of polymers to environmental factors, however only recently has their use in the monitoring of mechanical properties been explored. Silica optical fiber sensors have already demonstrated great potential for advanced composites in spacecraft and other critical structures. However, polymer optical fiber (POF) sensors provide many attractive characteristics beyond those of glass fibers, providing information not obtainable from previous sensors as the structures undergo significant changes. The significant advantage of the plastic optical fiber sensor as compared to either glass optical fiber or electrical strain gages is their high strain to failure. Therefore, POF sensor systems will potentially offer a larger strain range measurement capability along with more long-term survivability.
Section photograph of embedded optical fiber sensor
in woven composite laminate after low velocity impact.
|
