Interfacial nanocomposite sensors (sQRS) for the core monitoring of polymer composites’ fatigue and damage analysis

Abstract

The quick development of the smart factory and prognostic and health management (PHM), in the fields of aeronautic, automotive and green energies, is evidencing a need for sensors able to monitor the behavior of composite materials all along their life at the closest of the matter. In situ fabricated conductive polymer nanocomposite (CPC) sensors are bringing an interesting solution to this prospect as they can be integrated homogeneously in the core of composites to probe their deformations and damage. In particular fatigue which is one important mode of failure of polymer composites can be monitored from early signs of damage until the final breakage by analyzing the piezo-resistive response of quantum resistive strain sensors (sQRS) made of carbon nanotubes. We have developed all these aspects in the paper taking the example of a classical glass fibers/epoxy composite instrumented in its core with two sQRS to monitor its short and long term fatigue behavior.

Multifunctional Carbon Nanotubes Enhanced Structural Composites with Improved Toughness and Damage Monitoring

“…A layer of 60 µm of 1.5 wt % CNT masterbatch was intercalated into the center of a glass fiber epoxy composite plate. This conductive layer was used as an in situ quantum resistive strain sensor (sQRS) [48] in these samples. The proportion of glass fiber was 55 wt %.…”

“…This interesting feature allows the in situ measurement of strain and damage of the composite, and Chou et al [45] showed that it was possible to model the appearance and the development of cracks during damage accumulation with a finite element method. Moreover, the nature of the electrical pattern during mechanical solicitations makes possible to distinguish between reversible elastic behavior, non-reversible plastic deformation and damage due to cracks ignition and propagation, validating the possibility of health monitoring [41][42][43][44][45][46][47][48][49].…”

“…Particularly in the boating, aeronautic, wind energy and automotive industries, the increasing use of structural composites have razed a need for the improvement of performances and the reliability of these materials. In this context CNTs have revealed to be promising multifunctional nanofillers, able to simultaneously enhance mechanical properties [36][37][38][39][40], monitor the strain [41][42][43] and predict the appearance of cracks [44][45][46][47][48][49], leading to SHM capability [50][51][52]. But the exceptional theoretical mechanical properties of CNTs resulting from a unique tubular configuration and sp 2 carbon bounding [4], although confirmed experimentally on small bundles of CNTs [53][54][55], are hardly transferrable to the composite without deterioration.…”

“…Later on, the use of a 3D conductive network within the epoxy matrix to monitor the damage of glass fiber-reinforced composite (GFRC) was demonstrated by Chou et al [41,45]. More recently, localized patches of conductive polymer nanocomposites were inserted in the core of composites made of epoxy reinforced with glass [48,51,52] and flax [64] fibers to design smart composites able to monitor structural health (SHM). The conductivity in CPC is mainly ruled by the tunneling effect, which is very sensitive to the evolution of the average gap between carbon fillers [65][66][67][68].…”

Damage monitoring of adhesively bonded composite-metal hybrid joints using carbon nanotube-based sensing layer

“…Due to their extraordinary properties, carbon nanotubes are of particular interest in a variety of applications such as improving mechanical properties [13][14][15], self-sensing composites [16,17], structural health monitoring [18][19][20][21][22] and flexible sensors [23,24]. Thostenson et al [25] added carbon nanotubes to an epoxy resin while manufacturing a composite to monitor the health of mechanically fastened composite joints and the characterization of the damage mode.…”