Study of the Effect of Accelerated Ageing on the Properties of Selected Hyperelastic Materials

Hyperelastic materials, which include various types of rubber, are widely used in industry (such as the automotive industry). Their main disadvantage is the loss of their original properties over time due to environmental factors (called ageing). The ageing process is long-lasting, which is why so-called accelerated ageing is used when studying the effect of ageing on material properties. Accelerated ageing is realized with a higher intensity of the ageing agent, e.g., by irradiating specimens with UV radiation or by holding them at elevated temperatures. In the literature, there is a lack of parameters for constitutive models that take into account the effect of ageing on material properties. This paper presents the process of determining the parameters for a selected constitutive model using two commonly used rubbers in industry: chloroprene (CR) and ethylene-propylene-diene (EPDM). Before determining the material parameters, the samples were subjected to accelerated ageing at 100 °C for periods of 7, 21, and 35 days. Stress–strain curves were then determined from a tensile test and the parameters of the constitutive model were determined using the non-linear least squares method. Finally, numerical validation of the obtained values was also carried out.