Mullins Effect in Filled Elastomers Revealed by Stretching Measurements with Various Geometries

多様な伸長モードを用いたフィラー充填エラストマーのマリンス効果の研究

2018-03-26

2018-03-26

In this thesis, the Mullins effect and induced anisotropy by stress-softening in filled elastomers are characterized by the stretching measurements in various geometries. The present study reveals the influences of (1) degree and type of deformation, (2) filler content, (3) filler-polymer interaction, and (4) crosshead speed on the Mullins effect, and the anisotropy in energy dissipation, and directional energy dissipation, respectively. The dissipated energy (D), residual strain (εr), and dissipation factor (Δ; the ratio of D to input strain energy) in the loading-unloading cycles for silica filler-reinforced elastomers were evaluated as a function of the maximum stretch in cyclic loading (λm) using various modes of stretching. Both D and εr increase with an increase in λm for each type of deformation. When compared at the same λm, D and εr increase in the order of equibiaxial, planar, and uniaxial extension. The λm dependences of Δ in various geometries of extension fall into a single curve when the first invariant of deformation tensor (I1,m) is employed as a variable. Δ steeply increases with an increase in I1,m in the small deformation regime of I1,m < 3.2, which reflects the rupture processes of the inherent structures including the filler networks and the filler-polymer interface. In contrast, Δ levels off in the large deformation regime of I1,m > 3.5, which is caused by the friction between the fillers and the rubber matrix after the inherent structures are fully destroyed. Δ also increases with an increase in the filler content and the introduction of silane coupling agent as a result of an increase in friction loss at the filler-polymer interfaces. In the investigation of anisotropy induced by stress-softening, the following important features of the anisotropic Mullins effect have been revealed: (1) The damage in the direction of the larger pre-strain (x-direction) (D0, directional energy dissipation with θ = 0°) was governed only by the maximum stretch in the corresponding direction, and it was independent of the degree of the pre-strain in the other direction (y-direction); (2) The damages in the directions unparalleled to the x-direction (Dθ, directional energy dissipation with θ = 45° or 90°) were influenced by the degrees of the pre-strains in both x- and y-directions; (3) Dθ was generally expressed as a sum of the contributions of the strains in the two directions, i.e., the quadratic effect of the pre-strain in x-direction, and the linear effect of that in y-direction. (4) The anisotropy of damage in Mullins effect (fθ; the ratio of D0 to Dθ) increased with an increase in the anisotropy in the pre-strain field. The values of Dθ and fθ increased with an increase in the volume fraction of the silica (Φ), and Dθ and fθ for the specimens without silane coupling agent (SCA) were considerably lower than those for the specimens with SCA.

博士（工学）

京都工芸繊維大学

14303甲第868号

http://hdl.handle.net/10212/2463

eng

ETD

Thesis or Dissertation

Thesis