[2C7] From cradle to the grave: eddy current testing for manufacture and remanufacture of carbon fibre composite structures
E Arabul¹, M Mussatayev¹, R Palazzetti², P Saunders³ and R Hughes¹
¹University of Bristol, UK
²Politecnico di Milano, Italy
³National Composites Centre, UK
Carbon fibre-reinforced polymer (CFRP) composite components can be manufactured with a near infinite variety of materials, stacking sequences, manufacturing methods and conditions, shapes and sizes. There is so much variety in these manufacturing processes that building confidence in the as-manufactured quality of the components is extremely challenging. Detailed non-destructive evaluation is needed to accurately make the critical design features, for example fibre alignment and manufacturing flaws, to confirm that parts are fit for purpose; however, few techniques besides X-ray computed tomography (CT) have the sensitivity and resolution to meet these non-destructive evaluation (NDE) requirements. In addition, CFRP manufacturing is an additive process, which therefore lends itself to in-line monitoring, where flaws can be identified early and can be removed or discarded quickly, eliminating waste and building confidence in the as-manufactured structural integrity. While X-ray CT and ultrasonic testing (UT) techniques are ill suited to in-line monitoring, eddy-current testing (ECT) techniques are possible due to the electrical conductivity of the carbon fibres of CFRP. Non-contact ECT inspection techniques are therefore well suited to monitor variations in CFRP electrical properties, which correlate with fibre density variations. In this paper, recent advances and results are presented on the development of ECT inspection techniques for in-line monitoring of the automated fibre placement (AFP) manufacturing process. The results demonstrate and quantify the capability of ECT inspection techniques for monitoring and detecting structural variations and defects in uncured AFP CFRP structures. The results are also presented from ECT inspections of CFRP samples remanufactured from reclaimed woven coupons and tested pre- and post-fatigue testing. The ECT results are shown to successfully identify resin-rich regions as potential sites of mechanical failure and detect quantifiable changes in the fatigued samples.
