Internal defect analysis in composite materials by active thermography

Abstract

The aeronautical industry found in carbon fiber reinforced composite materials an excellent ratio of low weight and high strength making it an attractive option to replace aluminum in aircraft structures. These composites, however, still present technical challenges regarding their manufacturing. For safety reasons, composite components must be inspected after manufacturing and during operation, in order to check for internal defects that may cause mechanical failure and accidents.Currently, in most practical cases the internal defect verification process is performed by a trained inspector, responsible for identifying and classifying defects with the aid of ultrasonic equipment. The current process is slow, intense, repetitive, and the evaluation depends on the inspector's subjective interpretation. It is estimated that the inspection rate of a handheld ultrasonic probe is approximately 0.5m²/hour, since the inspector must cover the inspection area with a sensor whose contact area is less than 1 cm². In addition to the delay in the delivery of the aircraft, there is a considerable risk of missing defects.The current project presents a methodology for detection of internal defects in composite materials, with higher objectivity and reproducibility. The primary objective of the research is the validation of active thermography as a robust composite inspection technique. A thermographic camera will be used to measure the surface temperature of the material and an optical excitation source will be responsible for providing the heat input. The signals from the test will be processed by a computational algorithm. The results will be analyzed and compared to reports obtained via ultrasonic inspection. At a later development stage, a functional prototype of the system, consisting of hardware and software, will be constructed and validated in a representative industrial environment. (AU)