In this study, silicon carbide fiber was proposed as a sensor for detection and localization of low-velocity impacts on composite structures. Semi-conductive silicon carbide fibers have excellent piezoresistivity and good mechanical properties, so their potential as a sensor for low-velocity impact detection and localization was investigated by attaching it on the surface of a composite panel. By measuring the resistance change of the silicon carbide fiber sensor due to low-velocity impacts on the composite material, impacts signals were obtained, and the resistance changes of the silicon carbide fiber sensor were acquired by conversion to voltage using a Wheatstone bridge circuit. The impact signals acquired using the silicon carbide fiber sensors were investigated to analyze the repeatability for impacts at the same location point and impact distinguishability at different points. Finally, impact localization based on a reference database using the silicon carbide fiber sensors attached to the composite panel was performed, and a total of 20 impacts were localized with an average error of 16.2 mm and a maximum error of 39.5 mm for a test section with planar dimensions of 200 mm × 200 mm.

This investigation highlights different surface functionalization processes of multi-walled carbon nanotubes (MWCNTs) and their effects on mechanical properties of polyetherimide nanocomposite. Surfaces of MWCNTs were modified by chemical process and by low-pressure plasma process. There is a significant change in physicochemical characteristics of MWCNTs after chemical and low plasma treatment evident from scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy studies. Due to surface modification of CNTs, there is a significant change in surface morphology and increase in oxygen functionalities such as C=O, C-O, and COOH especially evident in low-pressure plasma treatment; however, differential scanning calorimeter and thermogravimetric analysis studies reveal that thermal properties of the composite do not alter as such. There is a significant increase in mechanical properties of high-performance polymeric nanocomposites when surface-functionalized MWCNTs are dispersed in polymeric matrix; however, surface characteristics of the composite remain almost unchanged evident from contact angle and surface energy studies.