Correlative Light-Electron Fractography of Interlaminar Fracture in a Carbon–Epoxy Composite

Abstract

This work evaluates the use of light microscopes (LMs) as a tool for interlaminar fracture of polymer composite investigation with the aid of correlative fractography. Correlative fractography consists of an association of the extended depth of focus (EDF) method, based on reflected LM, with scanning electron microscopy (SEM) to evaluate interlaminar fractures. The use of these combined techniques is exemplified here for the mode I fracture of carbon-epoxy plain-weave reinforced composite. The EDF-LM is a digital image-processing method that consists of the extraction of in-focus pixels for each x-y coordinate in an image from a stack of Z-ordered digital pictures from an LM, resulting in a fully focused picture and a height elevation map for each stack. SEM is the most used tool for the identification of fracture mechanisms in a qualitative approach, with the combined advantages of a large focus depth and fine lateral resolution. However, LMs, with EDF software, may bypass the restriction on focus depth and present enough lateral resolution at low magnification. Finally, correlative fractography can provide the general comprehension of fracture processes, with the benefits of the association of different resolution scales and contrast modes.

3-D reconstruction by extended depth-of-field in tribological analysis: Fractal approach of sliding surface in Polyamide66 with glass fiber reinforcement

“…This technique consists on acquisition of sequence pictures with a digital camera in an optical microscope with progressive focusing with a regular displacement intervals, and taking the best-focused pixels for each x-y position throughout the entire stack to construct a focused picture to provide a reliable elevation map (15]. This technique has been applied to quantitative fractography and is very well supported by the set of articles developed by Hein et al [14][15][16][17][18]. Nowadays there are several freeware solutions for EDF reconstruction.…”

5. Digital tribology and the Industry 4.0 – a note

“…The limitation most often referred to is the depth-of-field. Nevertheless, topography of the sliding surface can be analysed with OMs with the aid of extended depth from focus reconstruction methods, with several advantages over: confocal scanning microscopy, scanning electron microscopy and atomic-force microscopy [13]. Issues related to image processing and analysis, as well as microscopy parameters, are discussed topics in the three examples presented below:…”