Isabelle Pillin

Engineering of graphene/epoxy nanocomposites with improved distribution of graphene nanosheets for advanced piezo-resistive mechanical sensing

Conductive nanostructured composites combining an epoxy polymer and graphene have been explored for applications such as electrostatic-dissipative, anti-corrosive, and electromagnetic interference (EMI) shielding, stealth composite coating and specifically for sensors. For many of these applications, the limits of dispersion of graphene nanosheets and the interface between fillers and matrices have affected their electrical, structural and mechanical properties. To address these problems, we present the use of a dimethylbenzamide (DMBA)-based hardener to modify the surface of reduced graphene oxide (RGO) and create a 3D architecture with a micro-porous structure. DMBA is applied to provide two functions: one is to act as a stabilizer to avoid restacking of graphene sheets during the reduction process, and the second is to provide a linkage between RGO and epoxy for the formation of homogeneous nanocomposites. Thin films of conductive polymer graphene composites (CPCs) were prepared using a simple doctor blade method, while piezoresistive sensors were prepared by spraying to demonstrate their application for mechanical strain sensing. The electrical properties of the composites as a function of graphene fillers were shown to significantly increase from 1012 Ω sq−1 for neat epoxy to 106 Ω sq−1 for 2 wt% RGO in epoxy composites, while the modulus calculated using nanoindentation exhibited a 43.3% enhancement from 3.56 GPa for epoxy to 6.28 GPa for the composites containing 2 wt% graphene. The results of piezo-resistive performance for mechanical strain sensing under both static and dynamic strain modes showed good sensitivity with a gauge factor (GF) of 12.8 and a fast response time of 20 milliseconds. A minor loading/unloading hysteresis loop after 1000 cycles indicated good reversibility and reproducibility of the sensors. Excellent reproducibility, long-term stability and reliability of the sensing devices are confirmed working without decay of sensitivity after a 6-month exposure to ambient atmosphere. The results obtained suggest that these types of piezo-resistive sensors based on RGO/epoxy CPCs due to their simple, scalable and low cost production could lead to the development of high-performance mechanical strain sensors for a broad range of applications including real-time monitoring, wearable electronics, and structural health monitoring (SHM).

Robustness of carbon nanotube-based sensor to probe composites' interfacial damage in situ

A carbon nanotube-based sensing interphase, acting as a quantum resistive sensor, has been homogenously integrated in glass fibres–epoxy composites to investigate their interfacial damage in situ. Depending on the chemical constitution of the transducer, the strain monitoring of composites via quantum resistive sensor can be limited to the elastic domain of deformation over which it is progressively destroyed, or it can allow collecting information on the damage in the nonlinear range. Combined macro- and micromechanical tests on composites with quantum resistive sensor interphase appear helpful to develop smart composites with health monitoring capability.

The effects of PHBV-g-MA compatibilizer on morphology and properties of poly(3-hydroxybutyrate-Co-3-hydroxyvalerate)/olive husk flour composites

Abstract The paper provides some experimental data on the effects of a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) grafted maleic anhydride (PHBV-g-MA) used as the compatibilizer for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/olive husk flour (OHF) composites prepared by melt compounding. The natural filler was added to PHBV at various contents, i.e. 10, 20, and 30 wt%, while the amount of PHBV-g-MA was 5 wt% based on neat PHBV. Morphology, contact angle measurements, water absorption (WA), mechanical, viscoelastic, and barrier properties of the various composites were investigated with and without the compatibilizer. The study showed through scanning electron microscopy that the addition of PHBV-g-MA to PHBV/OHF composites resulted in better and finer dispersion of the filler in the matrix, even at a higher content ratio, indicating improved affinity between the components. This is in agreement with the decrease in both surface energy and WA. Furthermore, tensile and dynamic mechanical measurements indicated a reinforcing effect of OHF in PHBV composites, being more pronounced in the presence of PHBV-g-MA. The barrier properties against oxygen and water vapor were also improved for the compatibilized composites.