Health monitoring of composites embedded with magnetostrictive thick film withoutdisassembly

Abstract

A new method of detecting delaminations in a composite structure embedded withmagnetostrictive particulate sensors is presented in this paper. The main advantages of thismethod are that it is non-contact, requires access to only one side of the structure, does notneed disassembly, and is free of mechanical coupling errors. The composite structure ismade of several carbon-fiber-reinforced-polymer (CFRP) layers and one layer ofmagnetostrictive thick film. To make the fabrication of composite structure simple andpractical, a special magnetostrictive thick film whose thickness is comparable to thethickness of CFRP layers was developed. The magnetostrictive thick film consists of finemagnetostrictive particles uniformly distributed in a binding polymer, preferably curedunder a bias magnetic field. Also, a compact non-contact sensing module that can be usedto scan the surface of a composite structure was developed that consists of a U-shapedmagnetic core with excitation and sensing coils on the two arms of the core. Amathematical model for sensing delamination in composite structures with anembedded magnetostrictive thick film layer was developed. Extensive experiments wereconducted to validate the model. The open circuit voltage induced in the sensing coilchanges significantly, in the range of 50–250 mV, in the presence of delamination.