Piezoresistivity in Micro Carbon Fiber Silicone Composites for Electrical Resistance to Strain Sensing

Abstract

In order to develop a cost-effective carbon fiber reinforced polymer sensor for compressive strain monitoring, a study was carried out to assess electrical and piezoelectric properties of samples containing five different carbon fiber weight percentages. Testing focused on sensing ability throughout measurement of resistivity: (1) when submitted to uniaxial variable compressive strain; (2) to time prolonged relaxation at constant strain; (3) and influence of environment temperature on measurements. Results enabled the possibility of usage for live monitoring of samples by determining sensitivity values of each sample being tested. Electrical resistance measurements assessment test results, show real time resistivity change in respect to experienced strain. Further piezoelectric properties where determined. An exponential decay function was found in fractional resistance in respect to relaxation due to constant strain testing. The total amount of time needed for measurements to present an error less than 1% at the probes was determined and found to vary up to seven days. Strain reversibility of resistivity measurements varied according weight percentages of carbon fibers used in composite sample being tested. Samples were tested in situ for monitoring of displacement on foundations of a dwelling to be built, placed on foundation’s soil. The main objective here was to assess practical questions such as handling and how measurements could be made safely. Results demonstrated successful monitoring during construction phase with easy deployment on site, sensing each construction phase loading.

Creep evaluation and temperature dependence in self-sensing micro carbon polymer-based composites for further development as an Internet of Things Sensor device

“…Moreover, it has an advantage over contact electrodes regarding thermal behavior compatibility with the composite's polymeric matrix. 16 Measurements of R were made using a two-probe technique, 50 mm apart, measured along the intended operational deformation axis (see Figure 3). The selection of a two-probe electrode design was based on the simplicity of manufacture, as well as considerations in everyday use as a sensing unit when deployed for remote monitoring.…”

“…Research on the R behavior of self-sensing carbon fiber polymer composites (SSCFPC) has shown sensing ability to vary as a function of the weight ratio of micro-carbon fibers in a composite (wt%). Previous analysis by Miguel et al 16 found for wt% up to 13% of micro carbon fiber polymer composites (MCFPC), presented measurements of R with linear decreasing behavior. For wt% above 40% and incorporating approximately five times shorter fibers, R was found to have a linear increasing behavior.…”

“…23 Research on the effects of R in MCFPC led to the conclusion that this type of sensing ability can present negative or positive R according to the weight ratio of micro carbon fibers in the composite. 16,[23][24][25] Hussain et al 26 and Wang et al 27 found that electrical resistance decreases with increasing compressive stress. The authors applied the general effective medium theory 28 to the change in volume to evaluate the experimental data for conducting micro-carbon fibers within the composite's matrix and consider it to be arranged in a three-dimensional network.…”

“…The viscoelastic properties of this type of composite are known to result in irreversible values, as reported in previous works. 16,23,35 In this work, the dependence of R on the change in temperature is investigated in terms of the isotropic properties of the carbon fiber composite. These properties will be used to establish a relationship between R outputs and environmental loading conditions.…”

Piezoresistive Chopped Carbon Fiber Rubber Silicone Sensors for Shedding Frequency Detection in Alternating Vortex Streets

“…B and relaxing it to the same preload as in fig.1 C we get a similar change in resistance that follows the load, but with a negative gauge factor. Both resistance change tendencies for B and C seem to decrease as the sample is repeatedly deformed, which previous research hypothesize to be caused by either microcracking, rearrangement of conductive paths or bending of the fibers causing piezoelectric effects [26]. It is clear from the plots that the piezoresistive behavior of the material is not linear, and while some of this, such as additional peaks of increased resistance as the material is being unloaded, might be correlated to Poisson's effect [27] or tunneling [28], making a model for correlating the sensor readings to actual pressure is not novel.…”