Experimental determination of viscoelastic properties of a highly compressible porous materials imbibed with water

Abstract

-The experimental study of a highly compressible porous material, made of cellulose fibers, and imbibed with water, during stress relaxation tests on a rheometer, shows that the material relaxes when kept at constant strain as long as there are open pores. Using the relaxation curves, the behaviour under compression can be divided into two distinct zones, a poro-elastic one and a purely-elastic one, bounded by the zero-porosity limit. In the poro-elastic zone, the "non-hookean" stress-strain curve is fitted using Spriggs' expression of the elastic modulus dependence with porosity. Therefore, the elastic modulus of the porous material is expressed as an exponential function with two parameters: the elastic modulus of the fibers and the initial porosity of the material. For the purely -elastic zone the variation of stress is expressed as a sum of the residual stress obtained from the continuity equation and a Hookean stressstrain variation of a thinner material with the elastic modulus of the fibers -determined previously. The relaxation curves are fitted with a relationship between the decay stress and time, approximated with three terms of Prony series expansion of the generalized Maxwell model.

Synergetic Effect of Porous Elastomer and Percolation of Carbon Nanotube Filler toward High Performance Capacitive Pressure Sensors

“…This can be explained by the fact that pores within the whole volume of the PEMC can reduce the volume fraction of the elastomer. As the existence of pores led to reducing the viscoelastic property of the SEMC, a reversible sensor response could be achieved without noticeable hysteresis. , We also confirmed these viscoelastic properties of SEMC and PEMC using the standard solid model; a spring and the Kelvin–Voigt model are connected in series (Figures S4 and S5). In Figure d, the long-term stability and electromechanical durability of the PEMC were evaluated under 10000 cycles of repeated compression/release at ∼10 kPa (compressive strain of 70%).…”

Multiwalled Carbon Nanotube/Graphite Powder Film for Wearable Pressure Sensors with High Sensing Performance

“…The pores within the whole volume of the 5%MWCNTs@5%Gp also can reduce the volume fraction of the elastomer. As the existence of pores led to reducing the viscoelastic property of the conductive composite materials, a reversible sensor response could be achieved without noticeable hysteresis [ 34 ]. It is worthy to mention that the sensor presented gradual and smooth current changes at strain of 0%–200%–0%.…”

Instrumentation and preliminary evaluation of a drop tower tester for low and medium impact energy

“…The studies on the impact behavior of porous materials could help optimize their structural design for improved protective solutions. The assessment of the damping capacity of dry or imbibed soft, porous materials, is characterized by medium or low impact energy and large displacements [1] [8]. The geometry of the impactor (plane, sphere, ogive, etc.)…”

“…has also a critical influence on the response of the compressed material and can modify the deformation mechanism of the solid structure. Finally, it must be noted that the imbibition modifies the physical properties of the porous materials and their compression response when compared with the response of a dry material [8].…”