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research-article

A Model for Calculating Hyper-Elastic Materials Material Properties under Thermal Aging

[+] Author and Article Information
Ahmed Korba

Department of Aerospace Engineering and Mechanics, The University of Alabama
agkorba@crimson.ua.edu

Abhishek Kumar

Department of Aerospace Engineering and Mechanics, The University of Alabama
akumar16@crimson.ua.edu

Guoqin Sun

Department of Mechanical Design and Method, College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, China
sguoq@bjut.edu.cn

Dr. Mark E. Barkey

Professor, Department of Aerospace Engineering and Mechanics, The University of Alabama
mbarkey@eng.ua.edu

1Corresponding author.

ASME doi:10.1115/1.4037170 History: Received February 02, 2017; Revised June 18, 2017

Abstract

Understanding the degradation of material properties and stress-strain behavior of rubber-like materials that has been exposed to elevated temperature is essential for rubber components design and life time prediction. The complexity of the relationship between hyper-elastic materials, crosslinking density, and chemical composition presents a difficult problem for the accurate prediction of mechanical properties under thermal aging. In this paper, a new and relatively simple mathematical formulation is presented to expresses the change in material properties of hyper-elastic materials under thermal aging. The proposed formulation has been applied to a natural rubber. Testing was performed on more than 130 specimens that were thermally aged then subjected uni-axial tension and hardness tests. The aging temperatures ranged from 76.7 °C to 115.5 °C, and the aging times ranged from 0 to 600 hours. Based on the recorded experimental data, the natural rubber mechanical properties under thermal aging showed a similar behavior to the rate of change of the crosslinking density (CLD) with aging time and temperature. Three mechanical properties have been chosen to be studied in this paper: the ultimate tensile strength, the fracture stretch value, and the secant modulus at 11.0% strain. The proposed mathematical formulation is a phenomenological equation that relates the material properties with the change in CLD based on a form of Arrhenius equation. The proposed equation showed promising results compared to the experimental data with an acceptable error margin of less than 10% in most of the cases studied.

Copyright (c) 2017 by ASME
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