Detection of impact damage in glass fibre-reinforced polymer composites using a microwave planar resonator sensor

A novel non-destructive testing scheme was proposed for the detection of impact damage in glass fibre-reinforced polymer (GFRP) composites using a microwave planar resonator sensor. The sensor offers the advantages of small size, low cost and simple structure. It is an open-circuited λ/2 long microstrip line and the detection principle is material perturbation. Electromagnetic simulation verifies the sensor design. A GFRP specimen subjected to 5,10 and 20 J impact was examined. The 20 J impact damage was detected through line and two-dimensional scanning. The line scanning enabled accurate localisation of the damage, whereas the two-dimensional scanning facilitated more precise reconstruction of the surface damage features in addition to localisation. The sensor performance for detecting impact damage with lower energy levels was investigated by line scanning. It was found that the sensor could detect and locate 10 J impact damage. Principal component analysis was introduced to significantly reduce the false detection of the 5 J impact damage. It is well demonstrated that the proposed scheme could serve as an alternative method.