Tuesday November 28, 2023 Time: 3:30-4:30
This seminar will be held in ASE 2.134
Shawn A. Chester, Associate Professor Mechanical Engineering & Associate Vice Provost for Research New Jersey Institute of Technology
This talk discusses recent and ongoing research on the inelastic behavior of soft materials, specifically filled rubber-like materials and renewable degradable glassy polymers. The majority of the talk is related to understanding the combined Mullins effect – viscoelastic response of filled rubber-like materials. Filled rubber-like materials are widely used in engineering applications and are known to exhibit a rate-dependent non-linear inelastic behavior and stress-softening, also known as Mullins effect, is frequently encountered. In this work, we characterized and modeled the constitutive response of a handful commercially available filled rubber-like materials. We first perform a set of large-deformation uniaxial experiments at room temperature and at multiple rates. Those experimental findings are used to develop and calibrate a thermodynamically consistent constitutive model, which is then numerically implemented in a finite element package by writing a user material subroutine. The constitutive model is validated by comparing the results of an inhomogeneous experiment and simulation. A key finding of this work is that the mechanisms that cause the Mullins effect appear to be the main drivers of viscoelasticity.
Near the end of the talk, a bit of time is devoted to our initial work to characterize the effect of stress on photo-degradation, and thus on the mechanical performance of cellulose acetate. Renewable and degradable polymers have emerged in everyday applications ranging from mundane eating utensils to high-tech medical devices. Many of these polymers exhibit photo-degradation, which is the result of bond cleavage in the polymer backbone due to chemical reactions, where the rate of reaction can be influenced by several factors. One can find in the current literature preliminary findings on how degradation under stress-free conditions can affect the mechanical performance. However there is a gap in the literature, we are still lacking experimental data and an appropriate continuum level constitutive framework.
