Embedded fibre Bragg grating sensors in advanced composite materials

Fibre Bragg grating (FBG) sensors have been embedded in a number of advance d composite materials and fibre/metal laminates (FMLs). The post-fabricatio n FBG spectra were studied to examine the influence of manufacturing variab les (such as composite stacking sequence and resin flow during processing) on the final profile of the spectrum and the functionality of the FBG senso r. Distortion and broadening of the width of the FBG spectra were observed in several of the specimens. As a result of a strong nonuniformity of the s train field caused by local asymmetric loading of the sensor., pronounced s plitting of the spectra into multiple peaks was noted for FBG sensors embed ded in angle-ply configurations. In contrast, the FBG spectra for the unidi rectional specimens exhibited a single well-defined peak. Tensile tests car ried out on these specimens showed excellent linearity within the test regi me. However, for specimens exhibiting a multi-peak spectrum. it was observe d that these specimens showed a tendency to produce strain anomalies during the loading event. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.