Fracture initiation associated with chemical degradation: Observation and modeling

Byoung Ho Choi, Zhenwen Zhou, Alexander Chudnovsky, Salvatore S. Stivala, Kalyan Sehanobish, Clive P. Bosnyak

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)


The fracture initiation in engineering thermoplastics resulting from chemical degradation is usually observed in the form of a microcrack network within a surface layer of degraded polymer exposed to a combined action of mechanical stresses and chemically aggressive environment. Degradation of polymers is usually manifested in a reduction of molecular weight, increase of crystallinity in semi crystalline polymers, increase of material density, a subtle increase in yield strength, and a dramatic reduction in toughness. An increase in material density, i.e., shrinkage of the degraded layer is constrained by adjacent unchanged material results in a buildup of tensile stress within the degraded layer and compressive stress in the adjacent unchanged material due to increasing incompatibility between the two. These stresses are an addition to preexisting manufacturing and service stresses. At a certain level of degradation, a combination of toughness reduction and increase of tensile stress result in fracture initiation. A quantitative model of the described above processes is presented in these work. For specificity, the internally pressurized plastic pipes that transport a fluid containing a chemically aggressive (oxidizing) agent is used as the model of fracture initiation. Experimental observations of material density and toughness dependence on degradation reported elsewhere are employed in the model. An equation for determination of a critical level of degradation corresponding to the offset of fracture is constructed. The critical level of degradation for fracture initiation depends on the rates of toughness deterioration and build-up of the degradation related stresses as well as on the manufacturing and service stresses. A method for evaluation of the time interval prior to fracture initiation is also formulated.

Original languageEnglish
Pages (from-to)681-695
Number of pages15
JournalInternational Journal of Solids and Structures
Issue number2
Publication statusPublished - 2005 Jan
Externally publishedYes

Bibliographical note

Copyright 2008 Elsevier B.V., All rights reserved.


  • Chemical degradation
  • Fracture initiation
  • Fracture toughness
  • Material density change
  • Microcrack network

ASJC Scopus subject areas

  • Modelling and Simulation
  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Applied Mathematics


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