A micro-mechanical model for predicting the stress response of particulate filled elastomers
Abstract
Elastomers typically are filled with nanoscopic particulates to improve their mechanical properties, where these properties depend upon the concentration and the state of aggregation of the filler particles inside the elastomer. Due to the presence of these rigid particulates inside a deformable matrix, considerable kinematic heterogeneity is observed inside these materials. Simulation of the microscopic kinematic field for filled elastomers has been performed to determine how the microscopic kinematic heterogeneity is related to the macroscopic mechanical response. The finite element simulations were performed for single as well as aggregated particles. A cluster growth algorithm has been developed to generate aggregated particles and they have been characterized by a variety of morphological parameters. The predictions of the finite element model have been validated by comparing the small strain elastic modulus of filled systems with that predicted by the Einstein-Guth-Gold equation for single particles, employing the concept of occluded volume. Finite element simulations were performed for four different non-linear rubber models, three different filler structures and a wide range of particulate volume fractions. Significant deviations from the Einstein-Guth-Gold theory are observed at large strains and higher volume fractions, where the internal kinematic heterogeneity is a strong function of the filler structure, volume fraction as well as the type of stress-strain non-linearity exhibited by the rubber matrix. A physical picture is proposed to describe the effect of this heterogeneity on the macroscopic stress response of the elastomer and the observed deviations from the classical Einstein-Guth-Gold theory. It is shown that the primary factor affecting the deviation of the macroscopic stress-strain response from the classical theory is the coupling between the non-linearity in the rubber and the structure of the aggregated particles. A model is proposed for simulating the stress-strain behavior of any non-linear rubber filled with particulate fillers varying in aggregate size and structure.
Degree
Ph.D.
Advisors
Caruthers, Purdue University.
Subject Area
Chemical engineering
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