Broad area damage detection in composites using fibre Bragg grating arrays

This article reports on the development of a technique for broad area detection of structural irregularities in composites using an integrated fibre optic sensing network. The technique is founded on a broadband vibration-based methodology known as the structural irregularity and damage evaluation routine that uses features in complex curvature operating shapes to locate damage and other areas with structural stiffness variations. The original structural irregularity and damage evaluation routine methodology relied on impact excitation at a series of grid points on the structure with the response recorded using a small number of reference accelerometers to determine the operating curvature shapes. This methodology has been modified to allow for single-point or environmental excitation with measurement of the curvature shapes provided by a spatially dense network of fibre Bragg grating strain sensors' surface mounted on the structure. This modified approach is known as the inverse structural irregularity and damage evaluation routine and has been experimentally validated on an impact-damaged composite panel. The technique was then applied to a full size composite structure (ship's rudder) containing structural features, where it was shown to successfully locate impact damage.