CaltechTHESIS
  A Caltech Library Service

Micromechanical damage and fracture in elastomeric polymers

Citation

Heyden, Stefanie (2015) Micromechanical damage and fracture in elastomeric polymers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9HX19NS. http://resolver.caltech.edu/CaltechTHESIS:12202014-233824767

Abstract

This thesis aims at a simple one-parameter macroscopic model of distributed damage and fracture of polymers that is amenable to a straightforward and efficient numerical implementation. The failure model is motivated by post-mortem fractographic observations of void nucleation, growth and coalescence in polyurea stretched to failure, and accounts for the specific fracture energy per unit area attendant to rupture of the material.

Furthermore, it is shown that the macroscopic model can be rigorously derived, in the sense of optimal scaling, from a micromechanical model of chain elasticity and failure regularized by means of fractional strain-gradient elasticity. Optimal scaling laws that supply a link between the single parameter of the macroscopic model, namely the critical energy-release rate of the material, and micromechanical parameters pertaining to the elasticity and strength of the polymer chains, and to the strain-gradient elasticity regularization, are derived. Based on optimal scaling laws, it is shown how the critical energy-release rate of specific materials can be determined from test data. In addition, the scope and fidelity of the model is demonstrated by means of an example of application, namely Taylor-impact experiments of polyurea rods. Hereby, optimal transportation meshfree approximation schemes using maximum-entropy interpolation functions are employed.

Finally, a different crazing model using full derivatives of the deformation gradient and a core cut-off is presented, along with a numerical non-local regularization model. The numerical model takes into account higher-order deformation gradients in a finite element framework. It is shown how the introduction of non-locality into the model stabilizes the effect of strain localization to small volumes in materials undergoing softening. From an investigation of craze formation in the limit of large deformations, convergence studies verifying scaling properties of both local- and non-local energy contributions are presented.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:elastomeric polymers, fractional strain-gradient elasticity, micromechanical damage, non-local regularization
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Mechanics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Ortiz, Michael
Thesis Committee:
  • Ravichandran, Guruswami (chair)
  • Ortiz, Michael
  • Bhattacharya, Kaushik
  • Weinberg, Kerstin
Defense Date:13 October 2014
Record Number:CaltechTHESIS:12202014-233824767
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:12202014-233824767
DOI:10.7907/Z9HX19NS
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8749
Collection:CaltechTHESIS
Deposited By: Stefanie Heyden
Deposited On:09 Jan 2015 17:02
Last Modified:09 Mar 2016 17:37

Thesis Files

[img]
Preview
PDF - Final Version
See Usage Policy.

28Mb

Repository Staff Only: item control page