PSI - Issue 64

Alamgir Khan et al. / Procedia Structural Integrity 64 (2024) 539–548 Alamgir khan / Structural Integrity Procedia 00 (2019) 000–000

542

Cyclic loading

(PC)

30 mm

50 mm

50 mm

50 mm

(Multimeter)

(b)

(a)

Fig.1 (a) Testing setup and (b) electrode arrangment of MWCNT/NCB compostie.

2.2 Electrical resistivity, heat-treatment, and strength measurement of MWCNT/NCB composite fillers

The electrical resistivities of the CNCB1 and CNCB2 specimens were investigated at room temperature for 28 d, and all the specimens were kept in plastic sheets to ensure uniform curing conditions. The electrical resistance was measured at 28 d and after 3 d of oven drying in an oven at 60 °C using two probe electrodes (Xian Victor Instruments Co., Ltd.). The electrical resistivity was calculated using Eq. 1. = ( / ) (1) where is the electrical resistivity, is the measured resistance, is the specimen area, and is the difference between the two electrodes. The CAC control and CNCB1-CNCB2 specimens were subjected to the targeted temperatures using an electric furnace (model BLMT) purchased from Luoyang Boermante Experimental Electric Furnace Co., Ltd., China, with a maximum temperature capacity of 1400 °C. Each sample, including the control, was placed in a furnace, and subjected to a constant increase of 5 °C/min from the initial room temperature until the target elevated temperature was attained. After attaining the targeted temperature, the samples were placed inside for two hours to get a uniform temperature distribution. Subsequently, the specimens were allowed to cool down to the ambient temperature without any intervention, while the furnace underwent a similar passive cooling process. Afterword, the compressive strengths of CAC control and CNCB1-CCB2 specimens were investigated and loaded to failure at a constant loading rate of 0.5 kN/s to at normal, 200 °C and 400 °C temperatures to further investigate the piezoresistive behavior under five different repeatable cyclic compressive loading amplitudes. The frictional change in the electrical resistivity (FCR) was calculated using Eq.2. = / 0 =( − 0)/ 0 ×100 (2) where 0 is the initial electrical resistance before loading, and is the real change in electrical resistance under cyclic compression loading.