Novel application of ground penetrating radar for damage detection in thick FRP composites

This paper presents the first successful application of ground penetrating radar (GPR) to the inspection of thick (≥100 mm) fiber-reinforced composites. These thick composites are found in wind/tidal turbine blades and composite-hulled ships, where sufficient non-destructive testing (NDT) remains challenging. Polyester-glass specimens, ranging in thickness from 100 to 120 mm, were created with delamination-mimicking damage. Specimen thickness, damage depth location, antenna orientation and damage dryness were the test variables. Finite-difference time-domain simulations indicated the method's feasibility, and experimental results confirmed these findings. GPR effectively detected and precisely located dry, in-plane damage, with increased detectability for water-filled damage due to the enhanced contrast of electrical properties that creates the damage response in the signal. This capability is particularly advantageous for marine composites, where extensive damage may lead to water ingress. In a comparison with an ultrasonic inspection, GPR proved superior for the thicker composites (≥100 mm). As the first successful application of GPR to composite structures, these findings significantly advance the field of NDT of these materials.