Evaluating damage in smart composite laminates using embedded EFPI strain sensors

Extrinsic Fabry-Perot interferometric strain sensors were assessed for their sensing capacity and survivability via the surface mounting and die interior embedment in the carbon/epoxy beams. Artificial delaminations of two different sizes were used to simulate delamination. The embedded EFPI-SSs along with surface-mounted SGs were used to evaluate the effect of the delaminations on bending stiffness induced by quasi-static loading on a comparative basis. The response of EFPI-SSs was shown to be linear up to a bending strain of 0.5% and was in good agreement with the interpolated strains of surface strain measurements. The embedded EFPI-SSs were able to differentiate the effect of the tensile delaminations on bending stiffness. The interior strain data from embedded EFPI-SSs were shown to be very useful to extrapolate the strain difference on both sides of the delaminations as well as deducing local stresses.