Effect of the Strain Rate on Damage in Filled EPDM during Single and Cyclic Loadings.

Nicolas Candau,Jean-Luc Bouvard,Christophe Pradille,Edith Peuvrel-Disdier,Noëlle Billon,María Lluïsa Maspoch,Guillaume Corvec,Oguzhan Oguz

doi:10.3390/polym12123021

Abstract

The effect of the strain rate on damage in carbon black filled Ethylene Propylene Diene Monomer rubber (EPDM)stretched during single and multiple uniaxial loading is investigated. This has been performed by analyzing the stress–strain response, the evolution of damage by Digital Image Correlation (DIC), the associated dissipative heat source by InfraRed thermography (IR), and the chains network damage by swelling. The strain rates were selected to cover the transition from quasi-static to medium strain rate conditions. In single loading conditions, the increase of the strain rate yields in a preferential damage of the filler network while the rubber network is preserved. Such damage is accompanied by a stress softening and an adiabatic heat source rise. Conversely, increasing the strain rate in cyclic loading conditions yields in a filler network accommodation and a high self-heating whose combined effect is proposed as a possible cause of the ability of filled EPDM to limit damage by reducing cavities opening during loading, and favoring cavities closing upon unloading.

Highlights

The fracture behavior of rubber materials during service is widely affected by its thermomechanical history, in turn governed by the loading conditions
The effect of the strain rate on damage is of significance, especially when elastomers undergo severe loading conditions, like high frequency cyclic loading [1]
Chains are elastically active due to trapped entanglements, sulfur bonds, or bonds at filler interface. These elastically active chains are expected to experience some damage upon deformation via chains scission, breakage of chemical crosslinks, and breakage at filler interface

Summary

Introduction

The fracture behavior of rubber materials during service is widely affected by its thermomechanical history, in turn governed by the loading conditions. The effect of the strain rate on damage is of significance, especially when elastomers undergo severe loading conditions, like high frequency cyclic loading [1]. Such conditions are met in many industrial applications such as rubber fatigue in pneumatic tires [2], mechanical devulcanization of wastes rubber [3,4], cyclic compression of cellular elastomers [5], and dynamic loading of rubber springs [6]. The recent progress in automation of the testing methods and limited computational time due to algorithm improvements allows us to investigate damage mechanisms at larger strain rate range [7], expanding the investigation of damage behavior on a wider number of applications [8].

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