Fig. 1. Strain transfer models of a crack causing an infinitesimal displacement for a high (a) and a low (b) shear modulus sensing fiber.

Fig. 2. Schematics of the cable prototypes.

Fig. 3. Numerical model. Highlighted region represents the fixed displacement imposed to simulate the applied load; (a) first cable, (b) second cable.

Fig. 4. Calibration setup: test rig (a), linear actuator (b) and controller (c).

Fig. 5. Clamps in the test rig (a), CAD representation (b) and test cable insertion (c).

Fig. 6. Calibration data for the first (a), and the second (b), cable prototypes.

Fig. 7. Aluminium specimen in the tensile strength machine.

Fig. 8. Strain transfer of the first sensing cable (up) and second sensing cable (down). Horizontal lines: strains measured by the gauges. Stars: OBR measurements. Dashed lines: analytical model. Diamonds: numerical FEM model.

Fig. 9. OBR characterization of the strain response for the strain and temperature sensing cables. Horizontal dashed lines: real strain of the linear actuator.