Speaker
Description
The non-destructive testing (NDT) sector within aerospace composites is predominantly an end-process inspection approach and composite manufacturers report approximately 30% failure rates at the end-process inspection. Although some surface damage can be repaired, irreparable sub-surface defects usually cause high volumes of materials waste. Despite the benefits of identifying defects early, in-process inspection is not common in aerospace composites due to the high cost and slow speed of traditional NDT methods such as ultrasonic testing. High speed automated active thermography could make in-process inspection viable. Infrared Active Thermography (IRT) combines a thermal imaging camera with an excitation source to quickly measure a components temperature gradient response. This temperature gradient is administered by an excitation source as thermal waves, which flow into the material via diffusion. As a defect will have different thermal properties to the sound material, the diffusion rate differs between defect and sound material. This disparity allows for the quantification and detection of material damage. Therefore, IRT can be classified as non-contact and in turn has significant advantages other types of NDT techniques. However, the parameters associated with the excitation source are still an area of on-going research. These parameters include temporal (Pulse Duration, Excitation Frequency), energetic (Energy Density, Source Power, Spectral Range) and spatial (Heating Uniformity, Scan Velocity, Stand-off Distance) components and it is non-trivial to generalise these parameters for differing material and geometric variables, especially when the aim is quantitative analysis. The goal of this work is to compare between different IRT techniques, to facilitate the inspection of Carbon Fibre Reinforced Polymer (CFRP) components commonly seen in the aerospace sector. The techniques are quantitatively compared, in terms of effectiveness and efficiency when scanning representative aerospace grade composites that contain a wide range of defect depths and shapes.
