Dr. Richard D. Sudduth, President and Chief Scientist, Materials Research and Processing, LLC, United States

Speech Title: A New Description of Viscoelasticity that can be applied to Mechanical Properties such as Constant Strain Rate, Creep and Stress Relaxation Analysis

Abstract:Viscoelasticity in polymer compounds has often been simulated over the last half century by utilizing a mixture of both elastic and viscous components as described with elements of springs and dashpots. These simplified viscoelastic models have typically included combinations of Voight and Maxwell models either in parallel or in series. Unfortunately, these types of models have been found to be difficult to apply to real world applications that involve creep, constant strain rate and/or stress relaxation.

It was found that the new universal viscoelastic model described in this study effectively characterizes creep, constant strain rate and/or stress relaxation for most practical applications. This new model also characterizes the linear portion of secondary creep very well. The averaged intercept strain determined from secondary creep was also found to define the elastic component of a viscoelastic material.

The viscous component of a viscoelastic material was found to be characterized by a power law relationship between the instantaneous extensional viscosity and the strain rate. This relationship was found to be similar to the one commonly utilized between shear viscosity and shear rate for a non-Newtonian fluid. It was also found that the lowest viscosity was achieved with an efficiency of energy dissipation of n = 1. This result was found to be consistent with Scott-Blair who initially proposed that the value of n must exist in the range from 0(solid) < n < 1(liquid).