Non-destructive characterization of delaminated areas at interfaces between plies in carbon fiber/epoxy laminates with Foucault currents

Abstract

Carbon fiber epoxy laminates are extensively used in the aerospace industry as they offer a combination of high performance with relatively low weight. However, damage may occur in these materials, either at the manufacturing level or during use, which may affect their structural integrity. Among the type of damage which may occur, delamination is a common defect which causes a reduction in compressive strength and thus limits the life of laminated composites. If undetected, delamination may propagate during use due to mechanical loads and in the worst case may cause fracture of the material. Therefore, delamination in composite materials needs to be efficiently detected and accurately quantified for safety and economic reasons. Because of their heterogeneity, multi-layered structure and anisotropy, the inspection of composite materials remains difficult with conventional NDT methods. A method making use of Foucault currents, and relying on the principle of electromagnetic induction, can be adapted for the detection and characterization of damage in composite materials. The use of Foucault currents in characterizing delaminated areas at interfaces between plies in carbon fiber/epoxy laminates is addressed in this paper. It is demonstrated that Foucault currents can accurately detect and quantify delamination in CFRP materials. Furthermore, the potential of this technique for monitoring defect propagation in composite materials is discussed.