Monitoring of water absorption in CFRP laminates using embedded fiber Bragg grating sensors

Practical monitoring technologies are needed for evaluating water absorption/desorption in actual CFRP structures. In this study, the monitoring of water absorption in laminated CFRPs was demonstrated by a simple evaluation using fiber Bragg grating (FBG) sensors. The swelling strain and coefficient of moisture expansion (CME) of unidirectional (UD) laminates were estimated from the axial strain of FBGs. The measured swelling strains of cross-ply laminates agreed with that obtained from transient swelling analysis using the results of UD laminates. The swelling analysis showed that the change in the axial strain of FBG represents the swelling strain of the laminated CFRP. Moreover, another evaluation method employing changes in the FBG spectrum was proposed, and noted its possibility for laminated CFRP with almost 0 in-plane swelling strain. The present results suggested that the FBG measurement technique is useful for monitoring of water absorption in CFRP.