Electrical self-sensing of impact damage in multiscale hierarchical composites with tailored location of carbon nanotube networks

Abstract

Low-velocity impact damage in multiscale hierarchical composites comprising glass fiber weaves reinforcing a vinyl ester matrix with tailored location of multiwall carbon nanotubes is assessed through the changes of electrical resistance before and after impact. The location of the multiwall carbon nanotubes within the multiscale composite is controlled from manufacturing, rendering two hierarchical architectures. In the first one, as-received glass fiber weaves are used and the multiwall carbon nanotubes are only dispersed within the matrix, while in the second one the multiwall carbon nanotubes are dispersed within the matrix and also bonded to the glass fibers. Spatial electrical resistance maps are able to track the damage progression and growth of damage extension under consecutive impacts and the results are correlated to stresses determined by finite element analysis and ultrasonic C-scanning. The correlation between the electrical mapping and finite element analysis showed that the panels containing multiwall carbon nanotubes on the fiber are more sensitive to delamination and interfacial damage than the ones containing multiwall carbon nanotubes only dispersed within the polymer matrix.

Influence of electrode configuration on impact damage evaluation of self-sensing hierarchical composites

“…The oxidized MWCNTs possess –OH and –COOH functional groups and are held on the fiber surface by ester formation, hydrogen bonding, and epoxy ring opening reactions with the fiber sizing (Ku-Herrera et al, 2015). When these CNT-fiber weaves are used to manufacture hierarchical composites, the presence of MWCNTs on the fiber surface allows their participation in the conductive network formed within the CNT-modified polymer matrix, improving their electrical sensitivity to damage (Isaac-Medina et al, 2019).…”

“…Negative values of Δ R/R 0 have been associated with the redistribution of CNTs due to transverse shear stresses applied during impact events. Impact loading is known to cause delamination, where CNTs may separate from the GFs and agglomerate around the cracked zone; this could yield small resin pockets with a local accumulation of CNTs, thus decreasing the electrical resistance in localized zones (Isaac-Medina et al, 2019; Proper et al, 2009).…”

“…Since the multiscale hierarchical composites employed herein possess small nanotubes embedded within the polymer matrix, bonded to the fiber, and also bridging the fiber/matrix interface, the CNTs can infiltrate within the small interstices of the composite, yielding a very sensitive and non-invasive technique for impact damage detection. Thus, it seems reasonable that small matrix cracking, small fiber breakups, and even matrix plastic deformation can produce a change in the CNT network configuration, and consequently in the electrical resistance of the composite (Baltopoulos et al, 2015; Chung, 2001; Gao et al, 2011; Isaac-Medina et al, 2019; Viets et al, 2014). This could make this technique particularly sensitive to irreversible mechanisms (like plasticity) that are hard to identify by other techniques.…”

“…Techniques such as ultrasonic scanning, acoustic emissions, and X-ray scanning provide reliable information about the occurrence and localization of damage, but they are frequently costly, require complex instrumentation, and are not suitable for online assessment (Jan and Kim, 2017; Roh et al, 2016). As a non-destructive alternative which allows online and real-time evaluation, techniques based on the electrical response of carbon fibers (Abry et al, 1999; Angelidis and Irving, 2007; Chung, 2001; Schulte and Baron, 1989) and carbon-nanostructured fillers such as carbon nanotubes (CNTs) (Baltopoulos et al, 2015; Gallo and Thostenson, 2016; Gao et al, 2011; Isaac-Medina et al, 2019; Loh et al, 2009; Naghashpour and Van Hoa, 2015; Viets et al, 2014) or graphenic sheets (Lu et al, 2017; Moriche et al, 2016) have emerged to detect damage in advanced composite materials. Relying on the inherent electrical response is a technique which is fully integrated into the material and may allow monitoring impact damage in a non-invasive and online fashion, requiring minimum instrumentation (Alexopoulos et al, 2010; Roh et al, 2016).…”

“…Most analyses have been conducted on flat composite plates, and the choice of the surface where the grid of electrodes is applied is frequently arbitrary. While some authors have chosen to use a grid of electrodes directly on the impacted surface (Angelidis and Irving, 2007; Gallo and Thostenson, 2016; Isaac-Medina et al, 2019; Monti et al, 2011; Naghashpour and Van Hoa, 2015; Viets et al, 2014; Wang and Chung, 2006; Wang et al, 2005a, 2006a, 2006b), others have chosen the back (non-impacted) surface (Angelidis and Irving, 2007; Viets et al, 2014; Wang et al, 2005; Wang et al, 2006a). There are also a few works which have placed pairs of electrodes and circulated current through the thickness of the laminate (Viets et al, 2014; Wang et al, 2005, 2006a).…”