Eco-friendly laminates: From the indentation to non-destructive evaluation by optical and infrared monitoring techniques

S. Sfarra, C. Ibarra-Castanedo, C. Santulli, F. Sarasini, D. Ambrosini, D. Paoletti, X. Maldague

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


In this work, the combined effect of indentation damage and of manufacturing defects of a hybrid laminate including jute hessian cloth (plain weave) and hemp fibres in an epoxy matrix has been investigated. With this aim, various non-destructive evaluation (NDE) techniques have been employed, such as near-infrared (NIR) reflectography, infrared thermography (IRT), holographic interferometry (HI) and digital speckle photography (DSP). In particular, two different methods of heating were applied during IRT data collection: pulse thermography and square pulse thermography (SPT). The first one using a mid-wave infrared (IR) camera, while the second one using a long-wave IR camera. In the same way, two different cameras working into the near- and short-wave IR spectra were used, to compare different results from ∼ 0.74 to 14 μm. Data were processed applying principal component thermography (PCT), correlation and the robust second-order blind identification (SOBI-RO) algorithms. The latter is used for the first time to our knowledge in this work. The defects found were enhanced by image subtraction between the reflectogram and the transmittogram, distance transform and image fusion. In particular, data fusion from IRT and DPS images allowed clearly defining the extension of the indentation damage.

Original languageEnglish
Pages (from-to)175-189
Number of pages15
Issue number2
Publication statusPublished - Apr 2013
Externally publishedYes


  • digital speckle photography
  • holographic interferometry
  • hybrid material
  • image processing
  • infrared thermography

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering

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