Induced anisotropy by the Mullins effect in filled silicone rubber

Abstract

This study is concerned with the experimental characterization of anisotropy induced by the Mullins effect in a particle-reinforced silicone rubber. Experimental data concerning the influence of type and direction of initial loading on the subsequent stress softening are quite scarce. In this scope, a set of experimental tests were carried out on a filled silicone rubber. Uniaxial tensile tests and bulge tests were used to precondition the samples, i.e., to induce some primary stress softening. In both cases, subsequent uniaxial tensile tests were conducted on preconditioned specimens. The first set of experiments consists of a uniaxial tension path followed by uniaxial tension along different directions. It appears that the stress softening varies from a maximum in the same direction load to a minimum in the orthogonal direction, with respect to the first tensile load direction. Next, the bulge test is proposed as an original way to yield very different biaxial tensile strain-histories for first loading path. The fact that the biaxiality ratio varies from the pole (uniaxial tension) until the bulge border (planar tension), permits to analyze second tensile load curves in a material that experienced a more complex first load path. These experimental data allow to discuss the most appropriate criteria to describe the strain-induced anisotropy phenomenon.

Hyperelasticity with rate-independent microsphere hysteresis model for rubberlike materials

“…Its mechanical properties were previously investigated [7,20,21] and it was shown that this material exhibits stress-softening, occurring mainly during the first load, hysteresis and temperature dependent behavior.…”

Development and modeling of filled silicone architectured membranes

“…This material was already used in previous works and some non linear phenomena as hysteresis, relaxation [11,21] and induced anisotropy [13] were already studied. As illustrated by [21], the Mullins effect is the prevailing phenomenon so the experimental results focus on the study of this phenomenon.…”

“…The filled silicone rubber used in this study presents an induced anisotropy [11,13]. [19] developed a constitutive equation written with strain invariants to predict the behavior of this material.…”

“…8 a representation of the studied path on the bulge test [13]. b Biaxility ratio along the path equivalent model is able to well describe the strain states in a complex structure calculation i.e.…”

Effect of the Mullins softening on mode I fracture of carbon-black filled rubbers

“…Strain induced crystallization in filled natural rubber is known to retard crack growth, increasing significantly the critical energy release rate compared to non-crystallizing filled gum like SBR (Buist 1945 Diani et al 2009), exhibited by carbon-black filled rubbers, affects the resistance to crack propagation. The Mullins effect experienced by filled rubbers when first stretched above the maximum stretch ever applied, induces anisotropic softening (Diani et al 2006, Itskov et al 2006, Machado et al 2012 for instance) which consequences on the resistance to crack propagation remains unknown. Since the anisotropic softening may be characterized by a three-dimensional envelope that has been assessed on experimental evidences (Merckel et al 2012), it is relevant to study not only the impact of the softening magnitude but also its directional aspect on crack propagation.…”