Strain sensors in creep tests

This paper describes the behavior of block copolymer nanocomposites of poly(ethylene-co-methacrylic acid) (EMAA) during creep and recovery by utilizing the material's self-sensing capabilities. Carbon nanotubes (CNT), dispersed in the soft polymer EMAA, improve the matrix's mechanical, electrical, and thermal characteristics. The nanofiller enhances the creep behavior, reducing recoverable and creep strain. The modified Burger's model and the Weibull distribution function fit the experimental data well. The corresponding simulated settings show how the nanofiller affects the bulk matrix's creep and recovery capabilities. The study of the piezoresistive properties evidences a variation of electrical resistance in response to mechanical stress, which allows for detecting changes in the material structure. These structural rearrangements are generally not detectable in conventional stress-strain tests performed on soft polymers. The presence of irreversible damage in permanent strain is evident from the residual resistance when the system returns to rest after dynamic mechanical solicitation. Finally, the sensitivity of the nanocomposites to strain is greater when the filler concentration is lower.