Moisture contamination due to diffusion process changes the volumetric parameters of an adhesive layer material induced internal strain occurrence. This strain can be measured by FBG sensors embedded in the layer.
FBG sensors can be used for determination of moisture concentration in adhesive layer even when the amount of moisture is no higher than 2% of the sample weight.
Experimental relationship between measured strain and moisture concentration can be used for determination of estimated moisture concentration in the adhesive layer after both soaking and drying processes.