Mullins effect in polymer large deformation strain gauges

The possibility of making strain gauges with high sensitivity to changes in mechanical stress based on hard elastic films of isotactic polypropylene, with thixotropic polymer softening during cyclic deformation (Patrikeev-Mullins effect) and the dry crazing effect, is studied. Three options of rigid elastic film preparation using isotactic polypropylene for successive deposition of an adhesive layer of a solution of macromolecular compounds and an electrically conductive layer of a graphite dispersion are proposed. The optimal order of operations for manufacturing electrical sensors with high sensitivity to changes in mechanical stress has been established, including preliminary cyclic deformation in the air to form open micropores as a result of dry crazing . A mathematical model has been developed, which predicts the mechanical stress and/or the change in mechanical stress of film strain gauges based on the change in the electrical resistance of the conductive layer in the 6-35% strain range with up to 700 relative strain sensitivity.

Automated summary

This study investigates the possibility of producing strain gauges with high sensitivity to mechanical stress using hard elastic films of isotactic polypropylene. The films exhibit thixotropic polymer softening during cyclic deformation (Patrikeev-Mullins effect) and the dry crazing effect. Three methods for preparing rigid elastic films using isotactic polypropylene are proposed, involving the deposition of an adhesive layer and an electrically conductive layer. The optimal manufacturing process for electrical sensors with high sensitivity is determined, including pre-cyclic deformation to form open micropores. A mathematical model is developed to predict the mechanical stress and/or the change in mechanical stress of the strain gauges based on the electrical resistance change in the conductive layer, with up to 700 relative strain sensitivity in the range of 6-35% strain.