Effect of sensing distance of aluminum-coated FBG sensors installed on a composite plate under a low-velocity impact

This study investigates the effect of sensing distance on multiplexed aluminum-coated (Al-coated) fiber Bragg grating (FBG) sensors when they are applied to a carbon fiber reinforced polymer (CFRP) composite plate. The study involved a low-velocity impact test and its finite element analysis for the plate. The findings indicated that all the results from the test and FEA were consistent with each other. Additionally, the results revealed that permanently induced residual strains of all three Al-coated FBG sensors were linearly related to the sensing distance measured from the impact point. The findings also suggested that the linear relationship between the residual strains and sensing distances was closely related to the linear correlation between the sensing position and the maximum strains experienced by the composite plate. This implied that the impact information experienced by the composite structure could be quantitatively evaluated if the correlations between the structural deformation and residual strains with respect to the sensing distance were constructed in advance. Therefore, the correlation between the residual strains and the sensing distance examined in this study can improve the integrity of the proposed damage evaluation methodology and can be utilized as guidelines for designing a metal-coated optical fiber sensor (MCOFS) based damage evaluation systems for actual applications.