A general fractional model of creep response for polymer materials: Simulation and model comparison

Abstract

The creep deformation of polymer materials is a major concern to ensure the safety and reliability of structural designed parts. In this work, a novel fractional creep model is established by introducing the superb Almeida-Caputo fractional derivative into the traditional viscoelastic constitutive equation. The kernel function is determined by conducting several simulations of uniaxial creep tests, making it more flexible and reliable to provide excellent description of creep deformation. Compared to the traditional fractional model, the proposed model exhibits higher accuracy and better performance, and is found to have the ability to depict the nonlinear time-varying characteristic at accelerated creep stage.Furthermore, the physical significance of fractional order is explored by performing the sensitivity analysis of model parameters, the results revel that the order is closely associated with the evolution of material properties where the diagrams of creep deformation of polymer materials under elevated temperature and stress levels could be mirrored by the variation of fractional order.

Correlations between Microscale Indentation Creep and Macroscale Tensile Creep of Polymers

“…The limited stability of the higher-parameter models is documented also in the Supplementary Materials , where we calculated the covariance matrices for selected representative cases, showing that the covariances among parameters increased in the row S + D + 1 KV < S + D + 2 KV < S + D + 3 KV. Nevertheless, it is possible that some other higher-parameter models, such as generalized fractional models [ 50 , 51 ], might perform better.…”