The possibility of obtaining electrically conductive composites by applying carbon suspensions to fibrous materials by aerosol spraying and screen printing, on printing equipment, which ensures high productivity, is shown. A manufacturing technology has been developed and the electromechanical properties of layered fibrous composites based on knitwear and graphite dispersion designed for the manufacture of strain and stress sensors used in "wearable electronics", robotics and medicine have been investigated. In an experimental study, it is shown that the conductive path, that is, the length of the chains of contacting filler particles decreases with tensile deformation due to the growth of microcracks in the material. The electrical resistance of growing microcracks has much higher values than the resistance of deformable piezoresistive material. Cracks can open and close in various ways during bending, torsion, stretching and compression deformation. The electrical conductivity of fibers and filaments significantly depends on the localization of electrically conductive particles on their surface or in volume. The location of the conductive chains on the surface or in the volume of the filaments determines the dependence of the electrical properties of composites on the state of the environment (composition, temperature, humidity). Preliminary studies of filaments with electrically conductive components of various chemical nature (metals, metal salts, carbon in various allotropic forms) show that changes in temperature and humidity significantly affect the resistivity of the conductive fiber. The paper presents data on the effect of temperature and humidity on the electromechanical properties of elastic fiber composites with graphite. When stretched to 15%, the calibration coefficient GF is reduced by 2 times at 100% humidity. The different influence of air temperature in the range of 100C-700C on the deformation and strain sensitivity during cyclic deformation up to 15% and 30% has been established. The presence of two ranges of deformation sensitivity is due to the difference in the mechanisms of elongation of knitwear due to straightening and stretching of threads. Different deformation and strain sensitivity of composites in the ranges of small and significant strains, at different temperatures and humidity of the air, has been established. The strain sensitivity reaches 130, and the strain sensitivity is 12 MPa -1, which is an order of magnitude higher than the stress sensitivity of known polymer composites with various electrically conductive fillers.

1. Ryu H., Lee J.H., Khan U., Kwak S.S. et al. Sustainable direct current powering a triboelectric nanogenerator via a novel asymmetrical design. Energy Environ. Sci. 2018. vol. 11. pp. 2057–2063.

2. Monti M., Natali M., Petrucci R., Kenny J.M. et al. Impact damage sensing in glass fiber reinforced composites based on carbon nanotubes by electrical resistance measurements. J. ApplPolymSci. 2011. vol. 122. no. 4. pp. 2829–36.

3. Zhang H., Tao X.M., Yu T.X. Effects of Temperature, Relative Humidity and Washing Times on the Electrical Conductivity of Carbon-Coated Filaments. Sensors and Actuators A. 2005. vol. 126. pp. 803–807.

4. Zieba J., Frydrysiak M. Textronics System for Breathing Measurement. Fibres& Textiles. 2006. vol. 14. pp.43–48.

5. Wilson S.A., Jourdain R.P.J., Zhang Q., Dorey R.A. et al. New materials for micro-scale sensors and actuators: an engineering review. Mater SciEng R Rep. 2007. vol. 56. no. 1–6. pp. 1–129.

6. Huang Y., Tan G., Gou F., Li M. et al. Prospects and challenges of mini-LED and micro-LED displays. J. Soc. Inf. Disp. 2019. vol. 27. pp. 387–401. doi:10.1002/jsid.760

7. Hu N., Karube Y., Yan C. Tunneling effect in a polymer/carbon nanotube nanocomposite strain sensor. Acta Materialia. 2008. vol. 56. no. 13. pp. 2929–2936. doi:10.1016/j.actamat.2008.02.030

8. Chen Y., Pan F., Wang S., Liu B. et al. Theoretical estimation on the percolation threshold for polymer matrix composites with hybrid fillers. 2015. vol. 124. pp. 292–299. doi:10.1016/j.compstruct.2015.01.013

9. Mazaheri M., Payandehpeyman J., Jamasb S. Modeling of Effective Electrical Conductivity and Percolation Behavior in Conductive-Polymer Nanocomposites Reinforced with Spherical Carbon Black. Appl Compos Mater. 2022. vol. 29. pp. 695–710. doi: 10.1007/s10443–021–09991

10. Knite M., Teteris V., Kiploka A., Kaupuzs J. Polyisoprene-carbon black nanocomposites as tensile strain and pressure sensor materials. Sensor Actuat A. 2004. vol. 110. no. 1–3. P. 142.

11. Kawabe H., Natsume Y., Higo Y. et al. Nondestructive evaluation of crazes and microcracks on polymers by the elastic-wave transfer function method. Journal of materials science. 1993. vol. 28. pp. 3197–3204. doi: 10.1007/BF00354236

12. Zou F.Y., Xu Y.H., Chen H., Ye L. Study on the Sensing Property of Carbon-Coated Filaments. Advanced Materials Research. 2011. vol. 287. pp. 2911-2915. doi: 10.4028/www.scientific.net/AMR.287–290.2911

13. Yoshida A., Wang Y.F., Sekine T., Takeda Y. et al. Printed Low-Hysteresis Stretchable Strain Sensor Based on a Self-Segregating Conductive Composite. ACS Appl. Eng. Mater. 2022. vol. 1. no. 1. pp. 50–58. doi:10.1021/acsaenm.2c00010

14. Larimi S.R., Nejadb H.R., Oyatsi M., O’Briena A. et al. Low-cost ultra-stretchable strain sensors for monitoring human motion and bio-signals. Sensors and Actuators A: Physical. 2018. vol. 271. pp. 182–191. doi:10.1016/j.sna.2018.01.028

15. Tang J., Wu Y., Ma S., Yan T. et al. Sensing mechanism of a flexible strain sensor developed directly using electrospun composite nanofiber yarn with ternary carbon-based nanomaterials. Journal Pre-proof. 2022. vol. 22. S2589–0042. doi: 10.1016/j.isci.2022.105162

16. Bose A., Zhang X., Maddipatla D. ScreenPrinted Strain Gauge for Micro-Strain Detection Applications. IEEE Sensors Journal. 2020. vol. 20. no. 21. pp. 12652–12660. doi: 10.1109/JSEN.2020.3002388

17. Leseman Z.C. Design of a Microscale Optomechanical Load Cell for Micro-/Nanostructured Materials Testing Applications. Arabian Journal for Science and Engineering. 2022. vol. 47. no. 1. pp. 1053-1067. doi: 10.1007/s13369–021–06019–2

18. Mattmann C., Clemens F., Tröster G. Sensor for measuring strain in textile. Sensors. 2008. vol. 8. no. 6. pp. 3719-3732.

19. Hu Y. et al. A low-cost, printable, and stretchable strain sensor based on highly conductive elastic composites with tunable sensitivity for human motion monitoring. Nano Research. 2018. vol. 11. pp. 1938-1955.

20. Xiao X., Yuan L., Zhong J., Ding T. et al. High‐strain sensors based on ZnO nanowire/polystyrene hybridized flexible films. Advanced materials. 2011. vol. 23. no. 45. pp. 5440-5444. doi: 10.1002/adma.201103406

21. Boyko E.V., Kostogrud I.A., Smovzh D.V. The dependence of the graphene electrical resistance on mechanical deformation. Journal of Physics: Conference Series. IOP Publishing, 2020. vol. 1677. no. 1. pp. 012125. doi: 10.1088/1742–6596/1677/1/012125

22. Butera R.A., Waldeck D.H. The dependence of resistance on temperature for metals, semiconductors, and superconductors. Journal of chemical education. 1997. vol. 74. no. 9. pp. 1090. doi: 10.1021/ed074p1090

23. Király A., Ronkay F. Temperature dependence of electrical properties in conductive polymer composites. Polymer testing. 2015. vol. 43. pp. 154-162. doi: 10.1016/j.polymertesting.2015.03.011