Effects of stretching on the frictional stress of rubber

Abstract

In this paper, we report on new experimental results on the effects of in-plane surface stretching on the friction of Poly(DiMethylSiloxane) (PDMS) rubber with smooth rigid probes. Frictioninduced displacement fields are measured at the surface of the PDMS substrate under steady-state sliding. Then, the corresponding contact pressure and frictional stress distributions are determined from an inversion procedure. Using this approach, we show that the local frictional stress τ is proportional to the local stretch ratio λ at the rubber surface. Additional data using a triangular flat punch indicate that τ (λ) relationship is independent on the contact geometry. From friction experiments using pre-stretched PDMS substrate, it is also found that the stretch-dependence of the frictional stress is isotropic, i.e. it does not depend on the angle between stretching and sliding directions. Potential physical explanations for this phenomenon are provided within the framework of Schallamach's friction model. Although the present experiments are dealing with smooth contact interfaces, the reported τ (λ) dependence is also relevant to the friction of statistically rough contact interfaces, while not accounted for in related contact mechanics models.

Adhesion-induced fingering instability in thin elastic films under strain

“…This result implies that the larger the strain, the more θ = 0 is a favoured orientation, and thus the overall morphology becomes more anisotropic, in agreement with experiments. Finally, we note that the preference for deformation along the low-strain direction in comparison to the highstrain direction bears similarity with the results by Chateauminois et al, who studied friction on elastomeric surfaces with a pre-strain [36]. In these recent results, the authors found that the friction increases as a function of pre-strain, but that the increased friction is isotropic and independent of the indenter's geometry.…”

Memory effects in friction: the role of sliding heterogeneities

“…For smooth glass/PDMS contacts, we have also previously shown that the frictional shear stress τ is proportional to the local stretch ratio ζ within the contact, i.e. τ = ζ τ 0 , where τ 0 is the stress in the absence of stretch [13]. Such a feature could also be implemented in the numerical resolution of the problem.…”

“…In finite size contacts, deformation gradients are however invariably induced at the contact scale. Such gradients are expected to be especially strong in the case of finite size contacts between soft substrates such as rubbers or gels where frictional shear stresses are typically of the order of magnitude of the shear modulus [13]. As a consequence, the non-uniform deformation field of the contacting bodies should be specified to describe the state of the system.…”

Temperature effect on rubber gasket under high-frequency load

“…In addition, high temperature easily leads to the increase of cross-linking density and the decrease of flexibility of cross-linking links, which makes the main chain of polymer not arranged in an orderly manner, resulting in a small number of crosslinking links withstanding external forces, 8,9 thus making the material hard, brittle, inelastic, tensile strength, and tear strength reduced. 10,11…”

“…In addition, high temperature easily leads to the increase of cross-linking density and the decrease of flexibility of cross-linking links, which makes the main chain of polymer not arranged in an orderly manner, resulting in a small number of crosslinking links withstanding external forces, 8,9 thus making the material hard, brittle, inelastic, tensile strength, and tear strength reduced. 10,11 When the high frequency and large amplitude vibration of rubber gasket occurs, the vibration causes serious compressive stress concentration of rubber gasket. Under long-term load, the gasket root is in stress fatigue state, and then micro-cracks are generated, and gradually expand into deep cracks.…”