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Multi-walled carbon nanotube (MWCNT)/elastomer composites exhibit a piezoresistive behavior, i.e. their resistivity changes when they are subjected to mechanical loading. Thus, these materials can be used as strain or pressure sensors. In this paper, the effect of carbon nanotube weight fraction on the sensitivity and repeatability of the electrica...
Contexts in source publication
Context 1
... the IB, gage 1 measures the incident and reflected strains e i and e r . On the OB, gage 2 measures the transmitted strain e t at 0.4 m from the interface O. To measure distinctly the incident and reflective waves, gage 1 on the IB is bounded at 1.5 m from the interface I ( Figure 5). The signals are then conditioned, amplified and visualized using Labview ! . ...
Context 2
... whole test is filmed by a fast camera, with a frame rate of 100,000 images per second. A schematic view of the SHPB apparatus is given in Figure 5. ...
Context 3
... the IB, gage 1 measures the incident and reflected strains e i and e r . On the OB, gage 2 measures the transmitted strain e t at 0.4 m from the interface O. To measure distinctly the incident and reflective waves, gage 1 on the IB is bounded at 1.5 m from the interface I ( Figure 5). The signals are then conditioned, amplified and visualized using Labview ! . ...
Citations
... An electrical current I in the range of 10 μA to 3 mA was input through a linear measurement device. Thanks to this electronic scheme (see [2]) the range of measurement can be adapted by choosing an appropriate input current value. This setup gives the electrical voltage V as output, which in turn is used to calculate the electrical impedance at the macroscale Z = V/I. ...
... The Finite Element (FE) simulations were executed using the implicit general solver of the LS Dyna mechanical solver on a sample of radius The experimental engineering stress-strain curve σ(ε) (ε is the change in length to original length ratio) was provided by [2]. This enables to determine the material constants μ m and α m . ...
... Comparison of number of contacts from three different methods. Fig. 9. Experimental percolation threshold from [2]. ...
This paper presents the prediction of piezo-resistive behavior under quasi-static uniaxial compression loads using the Percolation Excluded Volume (PEV) approach. The PEV approach is supplemented by Finite Element (FE) simulations to calculate the displacements of Carbon Nano-Tubes (CNTs) embedded in a polymer matrix. The number of contacts between CNTs is determined by the minimum distance threshold (tunnelling distance). The FE model is based on experimental parameters and CNT data. The simulations carried out using the LS-Dyna solver made it possible to calculate the variation of electrical resistance, which was found to be in accordance with its experimental counterpart. The resistance increases when the CNTs are mostly oriented orthogonally to the loading direction. For other orientations, the resistance decreases.
Even though carbon nanotubes offer an excellent solution for the design of strain sensors, their widespread commercial utilization has been hampered by the unavailability of design rules, inconsistencies in their macro‐scale properties, and lack of understanding of the effects of various parameters on their characteristics. Nevertheless, many researches have been carried out to characterize elastomeric nanocomposites filled with carbon nanotubes in order to optimize their properties such as electrical conductivity and strain sensitivity range. This article reviews the effect of different parameters on the electrical properties of such nanocomposites, followed by the analysis of performances of elastomer strain sensors.
Flexible composite films with high power factors are the candidate for wearable energy harvesters, MWCNTs-SnSe/PEDOT: PSS ternary composite films were fabricated by a vacuum filtration method. The effects of cold-pressing on morphology, Raman spectra, and thermoelectric (TE) properties of the composite films were studied. For cold-pressed MSPPD10 ternary composite film, its conductivity and Seebeck coefficient both increase with increasing temperature. The results show that the PF is enhanced to 166.5 μW m⁻¹K⁻² for the cold-pressed MSPPD10 ternary composite film, which is 2.8 times the MSPPD10 (59.35 μW m⁻¹K⁻²) composite film without cold-pressing treatment. Besides, the TE property of cold-pressed MSPPD10 ternary composite film is better than that of SnSe or MWCNTs combined with PEDOT: PSS. The cold-pressed MSPPD10 ternary composite film had excellent flexibility, and the resistance only increases 12% after 1000 bends on an iron rod with a radius of 4 mm. In addition, the TE generator consisting of 4-leg cold-pressed MSPPD10 ternary composite films has a maximum output power of 13.5 nW at a temperature gradient of 30 K, showing great potential for flexible TE applications.
Piezoresistivity is an electromechanical effect characterized by the reversible change in the electrical resistivity with strain. It is useful for electrical-resistance-based strain/stress sensing. The resistivity can be the volumetric, interfacial or surface resistivity, though the volumetric resistivity is most meaningful scientifically. Because the irreversible resistivity change (due to damage or an irreversible microstructural change) adds to the reversible change that occurs at lower strains, the inclusion of the irreversible effect makes the piezoresistivity appear stronger than the inherent effect. This paper focuses on the inherent piezoresistivity that occurs without irreversible resistivity changes. The effect is described by the gage factor (GF), which is defined as the fractional change in resistance per unit strain. The GF can be positive or negative. Strong piezoresistivity involves the magnitude of the fractional change in resistivity much exceeding the strain magnitude. The reversible effect of strain on the electrical connectivity is the primary piezoresistivity mechanism. Giant piezoresistivity is characterized by GF ≥ 500. This critical review with 209 references covers the theory, mechanisms, methodology and status of piezoresistivity, and provides the first review of the emerging field of giant piezoresistivity. Piezoresistivity is exhibited by electrically conductive materials, particularly metals, carbons and composite materials with conductive fillers and nonconductive matrices. They include functional and structural materials. Piezoresistivity enables structural materials to be self-sensing. Unfortunately, GF was incorrectly or unreliably reported in a substantial fraction of the publications, due to the pitfalls systematically presented here. The most common pitfall involves using the two-probe method for the resistance measurement.
The electromechanical response of nanofiller-modified polymers subject to high-rate elastic loading has been little explored. In this paper, we address this gap by studying the piezoresistive response and mechanical properties of epoxy modified by three different kinds of carbon nanofillers when subject to high-rate elastic loading. Specifically, long high aspect-ratio epoxy rods were modified by carbon black, carbon nanofibers, and multi-walled carbon nanotubes and impacted in a split Hopkinson pressure bar. Electrical measurements during this loading reveal that the piezoresistive effect can be used to track elastic wave propagation in real-time, resistivity changes occur at the speed of sound of the nanofiller-modified epoxy, and the piezoresistive effect can be used to monitor stress wave properties. Further, dynamic modulus testing revealed that carbon nanofillers have a positive influence on the dynamic stiffness. These results show that piezoresistivity can be employed to provide real-time insight into the elastodynamics of self-sensing nanocomposites.
