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Novel Sensing Technique for Non Destructive Composites Monitoring
The real time non-destructive monitoring of stresses and temperature is one of the most demanded solutions in the field of sensor technologies.
One of the most prospective technologies addressing this problem is a novel sensing technique for non-destructive monitoring utilizing ferromagnetic wire inclusions presenting the high frequency magnetoimpedance, MI, effect quite sensitive to tensile stress and magnetic field 1. One of the advantages of this technology is that proposed free space microwave spectroscopy allows remote monitoring of external stimuli, like stress, magnetic field or temperature.
The glass-coated microwires with typical diameters from 1 to 50 μm can provide new functionalities such as improved mechanical and corrosive properties, adherence with polymeric matrices and biocompatibility 2.
In the present paper a novel sensing technique for direct non-destructive and non-contact monitoring of the composite polymerization utilizing ferromagnetic glass-coated microwire inclusions with magnetic properties sensitive to tensile stress and temperature is described. We provide in-situ studies of the evolution of the hysteresis loop of arrays consisting of Co- rich (Fe3.8Co65.4Ni1B13.8Si13Mo1.35C1.65) microwires during the composites matrix polymerization. We observed remarkable change of the hysteresis loops upon matrix polymerization: remarkable coercivity change and transformation of linear hysteresis loop into rectangular in the arrays with Co-rich microwires placed inside the matrix (see Fig.1a). Using the free space technique we observed considerable variation of the Transmission parameter of the microwires array in the range of 4-7 GHz upon the matrix polymerization (see Fig.1b).
Observed dependencies are discussed considering heating during the matrix polymerization measured using a standard thermocouple (Fig.1c) and the matrix shrinkage and their influence on magnetic properties and MI effect of glass-coated microwires.