Electrical self-sensing of strain and damage of thermoplastic hierarchical composites subjected to monotonic and cyclic tensile loading

Abstract

Electrical monitoring of strain and damage in multiscale hierarchical composites comprising unidirectional aramid fibers modified by multiwall carbon nanotubes and polypropylene as matrix is investigated. The key factor for electrical self-sensing in these thermoplastic composites is the formation of a multiwall carbon nanotube network, which is achieved by using two material architectures. In the first architecture, the multiwall carbon nanotubes are dispersed within the polypropylene matrix, while aramid fibers remain unmodified. The second architecture uses also multiwall carbon nanotube-modified polypropylene matrix, but the aramid fibers are also modified by depositing multiwall carbon nanotubes. Under tensile loading, the electrical response is nonlinear with strain ( ε), and the piezoresistive sensitivity was quantified by gage factors corresponding to low ( ε < 0.25%) and high ( ε > 0.3%) strain regimes. Such gage factors were 4.83 (for ε < 0.25%) and 13.2 (for ε > 0.3%) for composites containing multiwall carbon nanotubes only in the polypropylene matrix. The composites containing multiwall carbon nanotubes in the matrix and fibers presented higher piezoresistive sensitivity, with average gage factors of 9.24 ( ε < 0.25%) and 14.0 ( ε > 0.3%). The higher sensitivity to strain and damage for a specific material architecture was also evident during cyclic and constant strain loading programs and is attributed to the preferential localization of multiwall carbon nanotubes in the hierarchical composite.

Hierarchical Network Enabled Flexible Textile Pressure Sensor with Ultrabroad Response Range and High‐Temperature Resistance

“…This process not only was beneficial to the wettability and dispersibility of the CNT, but also made the CNT functionalized with negatively charged carboxyl group. [40,41] An EPD process [42] was then adopted to deposit FCNT on PI fiber fabric (Figure 1i). Under an electric field, these FCNTs migrated to the PI fiber fabric (anode) and were evenly wrapped to the fiber surface (Figure S4a, Supporting Information), as evidenced by the optical and SEM images of PI/CNT(EPD) (Figure 1j-l).…”

Hierarchical network enabled flexible textile pressure sensor with ultra-broad response range and high-temperature resistance

“…To improve the uniformity, a highly acidic and thermal oxidation process was used as the initial step to modify the CNT. This process not only was bene cial to the wettability and dispersibility of the CNT, but also made the CNT functionalized with negatively charged carboxyl group 34,35 . An EPD process 36 was then adopted to deposit FCNT on PI ber fabric (Figure 1i).…”