Influence of orthogonal prestrain on the viscoelastic behaviour of highly-filled elastomers

Abstract

International audienceHighly filled elastomers exhibit a complex nonlinear mechanical behaviour that is difficult to characterize experimentally. This paper presents a Dynamic Mechanical Analysis (DMA) method coupled with orthogonal prestrains, applied in two distinct steps. A localization operator between measurements at the arms of a cross shaped specimen and the stress and strain fields at its center was determined using elastic small strain finite element computations. The operator makes estimating the storage and loss moduli at the center of the specimen possible. A mathematical model is then fitted to the moduli values. These results are compared to DMA measurements of highly filled elastomers under uniaxial prestrain. Although the storage and loss moduli increase with the prestrain under both loadings, the nonlinear behaviour is quantitatively modified by adding an orthogonal prestrain. In addition, the modification of the behaviour under a horizontal prestrain is cancelled out by an increase of the vertical prestrain, which may be explained by fillers aligning in the direction of the prestrain

Prestrained biaxial DMA investigation of viscoelastic nonlinearities in highly filled elastomers

“…One can further remark that the model proposed here is different from the model developed in [9] or [10] where elements are added step by step in a Generalized Maxwell model, as a function of the increasing prestrain. The model here is described by the continuous spectrum H(t) with only one prestrain dependent parameter, and is not directly related to a Generalized Maxwell model [25].…”

“…In the present study, as in [10], the specimen will keep its cruciform shape (see a schematic view displayed in Fig. 5).…”

“…Recently, an experimental exploration of the outcome of a uniaxial and biaxial prestrain on the viscoelastic properties of highly filled elastomers has been proposed (see [9] and [10]). …”

“…Using an adaptive method, viscous elements were added to the model with increasing prestrain and were able to reproduce the increasing stiffness. Later, in [10] a biaxial prestrained DMA experiment was proposed where one of the axial directions of the cruciform specimen was blocked at a given prestrain level, and DMA tests were performed in the orthogonal direction. In this paper, we present biaxial DMA experiments superimposed on a fully biaxial prestrain.…”

Microstructure and deformation mechanisms of a solid propellant using 1 H NMR spectroscopy

“…The relations between the nonlinear mechanical behavior at the macroscopic scale and the microstructure at the scale of the fillers or the polymer chains have been explored [1][2][3][4][5][6]. However, direct experimental evidence of the physical mechanisms of deformation at the scale of the polymer network is difficult to obtain.…”