PSI - Issue 67

Oscar Aurelio Mendoza Reales et al. / Procedia Structural Integrity 67 (2025) 8–16 Mendoza Reales et. al./ Structural Integrity Procedia 00 (2024) 000 – 000

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distance between the measuring copper electrodes is governed by the thermal expansion coefficient (α), which is also a fair assumption. Given these assumptions, and that the thermal expansion of a cement-based material can be written as ε = αΔT, equation 3 can be rewritten as equation 5, presented below. ℎ = ( ∆ ) (5 ) GF values were obtained from the 25 °C experiments for both SSCC. These were assumed to be valid for the range of temperature studied since results in Fig. 5 showed that the FCR versus temperature behavior of both SSCC is similar between 25° and 75 °C. This allows plotting the expected increase in FCR with temperature due to thermal expansion, as presented in Fig. 6. Additionally, equation 4 allows plotting the expected effect of temperature increase when deformation is restricted. This is also presented in Fig. 6.

(a) SSCC1 (b) SSCC2 Fig. 6. Decoupling of the effects of thermal expansion and temperature on the studied SSCC.

It should be highlighted that results show that the behavior of the SSCC when exposed to increasing temperature is mainly governed by the increase in electrical conductivity of the material and that the thermal expansion effect plays a secondary role; nevertheless, if SSCC are expected to be used for accurate deformation measurements, this parameter should be included in the calibration equations of the material. 5. Conclusions The following conclusions can be drawn from the experimental data gathered in this work: • It was possible to obtain an SSCC with good repeatability and to determine its gauge factor at room temperature. • It was confirmed that the electrical resistivity of the SSCC with carbon nanotubes as conductive filler decreases when temperature is increased. • The range of temperatures studied in this work was found not to affect significantly the mechanical and piezo resistive performance of the SSCC. • The piezoelectric response of the SSCC was found to be repeatable in different temperatures in steady state. • The effects of thermal expansion can be considered secondary since changes in FCR due to temperature variations are governed mainly by the changes in electrical conductivity of the SSCC due to temperature variations. • The piezo-electric response of the SSCC should be studied in transient state in order to determine correction equations.