Multi‐Scale Analysis of Mechanical Properties of Amorphous Polymer Systems

Abstract

Use of proper constitutive equations for the intrinsic behavior of glassy polymers (including yield, strain softening and hardening) allows nowadays for analyzing the mechanical response of homogeneous and heterogeneous polymer systems in great detail. Analyses are performed on both the periodic RVE, representative volume element, level and, via a MLFEM, multi‐level finite element method, also on the macroscopic level of e.g. a notched, scratched tensile test bar. Introduction of a failure criterion, in this case the critical tri‐axial stress that initiates crazing, allows for the prediction of brittle‐to‐tough transitions, both as a function of temperature as well as of the absolute critical local material thickness. The analyses give clear suggestions towards possible directions to optimize the microstructure in heterogeneous polymer systems in order to obtain the ultimate toughness of polymers.

Challenges and Progress in High‐Throughput Screening of Polymer Mechanical Properties by Indentation

“…Compressive testing can be used to study the stress and strain behavior of the material beyond the yield point, as, in contrast to tensile testing, localization of the deformation phenomena is minimized. [52][53][54] As the load-displacement response and the contact area development during the indentation experiment depend on the yield stress, the strain softening and the strain hardening, [18] several findings from uniaxial compression tests combined with modeling are summarized here.…”

Modeling of the Postyield Response of Glassy Polymers: Influence of Thermomechanical History

“…[1][2][3][4][5] These efforts were motivated by the desire to predict mechanical properties and performance and to develop (numerical) tools for better understanding and, finally, improving properties of homogeneous, as well as heterogeneous, polymer systems. 6 A landmark in this area of research is the original paper of Haward and Thackray from 1968, 1 where they proposed to govern the large strain deformation of polymers below their glass transition temperature by two separate processes. The first process reflects the rate-dependent plastic flow related to temperature and stress-activated motion of chain segments, which is represented by an Eyring viscosity.…”

Processing-induced Properties in Glassy Polymers

“…10 In the last 15 years, a lot of effort has been invested by a number of groups at different universities into the development and validation of 3D constitutive models that can describe this localization behavior of glassy polymers, for example, in the group of Mary Boyce at MIT, [11][12][13] the group of Paul Buckley in Oxford [14][15][16] and in our Eindhoven group. [17][18][19] It was shown in subsequent quantitative studies 10,[19][20][21][22][23][24] that it is the large strain intrinsic behavior (yield, strain softening, and subsequent strain hardening) of the polymer that determines the macroscopic localization behavior, and thus failure. The model developed in our group proved to be capable of also predicting the long term static failure, 25,26 including a static fatigue limit when aging kinetics were taken into account.…”