Crack monitoring of tension members with distributed fiber optic sensor considering substrate strain redistribution and coating/fiber interfacial slip

An analytical model is proposed to describe the strain transfer from crack opening displacement (COD) of a tension member substrate to the distributed fiber optic sensor (DFOS), considering the DFOS/fiber coating interfacial slip and strain redistribution of the cracked structural substrate. The DFOS/fiber coating interfacial bond-slip relation is simplified by using a three-phase linear model, and the analytical expression of the substrate strain distribution of a tensile plate with different depth of crack is derived. The effect of the COD and crack depth on the strain distribution of the DFOS is obtained analytically, and tensile tests were also conducted on aluminum plates with different depth of precut crack to validate the developed model. Analytical results showed that the strain distribution of the DFOS is dependent on the COD and the crack depth, and the effect of the COD on the strain distribution of the DFOS is more significant than the crack depth. The analytical results of the developed model are in good agreement with those of the tensile tests.