Internal strain measurement by fiber Bragg grating sensors in textile composites

This paper is concerned with a study of internal strain measurement by fibe r Bragg grating sensors (FBGSs) embedded inside textile composites. First, on the basis of the measurement principle of FBGSs, the effects of transver se strain and temperature on the measurement results are discussed. A compo site model comprising an optical fiber, coating and resin was developed to determine the measurement effectiveness of an embedded optical fiber sensor by analyzing the strain held of the system under a uniform thermal load. F actors influencing the measurement effectiveness were considered including the elastic modulus and Poisson's ratio of coating material, tension stiffn ess ratio and the length of the host. Secondly, an experimental investigati on was carried out to determine the reliability of FBGSs embedded in textil e composites with different interfaces of fiber/coating and coating/resin a nd with two configurations, that is, single-ended and dual-ended. The measu rement errors induced by the deviation of position and direction of the sen sors were estimated. Finally, Volanthen's low-coherence technique was appli ed to measure the internal strain distribution along the length of FBGSs wh ich were embedded into textile composite. (C) 2000 Elsevier Science Ltd. Al l rights reserved.