Indentation deformation and fracture of thin polystyrene films

Min Li, Manuel L. Palacio, C. Barry Carter, William W. Gerberich

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Nanoindentation-induced deformation and fracture of thin polystyrene (PS) films on glass substrates were characterized using visible-light microscopy and atomic force microscopy (AFM). Two film thicknesses, 2 and 3.5 μm were studied. It was difficult to induce delamination in the 2-μm film while the 3.5-μm film delaminated easily under indentation loads of 150 mN and higher. AFM cross-section analysis of the deformation and fracture geometry revealed that the ratio of the delamination radius to contact radius was between 3 and 4. Analysis of the fracture surface on the glass side indicates that substrate cracking acts as a trigger for initiation and propagation of interfacial cracks. Crack-arrest marks and process-zone marks were also observed by AFM imaging. The interfacial fracture toughness, or practical work of adhesion, was evaluated following two methods based on the indentation-induced delamination and a process-zone analysis. The fracture toughness was found to be approximately 0.6 J/m2 for the 3.5-μm PS film on glass. AFM examination of the glass surface after indentation also showed fine flow lines around the indentation impression, indicating plastic deformation of glass.

Original languageEnglish (US)
Pages (from-to)174-183
Number of pages10
JournalThin Solid Films
Issue number1-2
StatePublished - Sep 2 2002


  • Atomic force microscopy
  • Indentation
  • Interfacial fracture
  • Polymer coatings

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