Dual-Configuration Fiber Bragg Grating Sensor Technique to Measure Coefficients of Thermal Expansion and Hygroscopic Swelling

摘要

We propose amethod based on the dual-configuration fiber Bragg grating (FBG) sensor to measure the coefficients of thermal expansion (CTE) and hygroscopic swelling (CHS) of polymeric materials. The Bragg wavelength shifts are documented in "two" small but different polymer-FBG assemblies while they are subjected to environmental loading conditions (temperature or moisture). The behavior of the infinite polymer/FBG assembly is reconstructed numerically from the data obtained from the two configurations. The coefficients, then, can be determined from the simple governing equation derived for the infinite assembly. The proposed method is implemented for an underfill material. The validity of measurements is corroborated by a commercially available tool, and the repeatability of measurements is verified by an experiment with a different configuration.