A Brief Discussion About Image Quality and SEM Methods for Quantitative Fractography of Polymer Composites

Abstract

The methodology for fracture analysis of polymeric composites with scanning electron microscopes (SEM) is still under discussion. Many authors prefer to use sputter coating with a conductive material instead of applying low-voltage (LV) or variable-pressure (VP) methods, which preserves the original surfaces. The present work examines the effects of sputter coating with 25 nm of gold on the topography of carbon-epoxy composites fracture surfaces, using an atomic force microscope. Also, the influence of SEM imaging parameters on fractal measurements is evaluated for the VP-SEM and LV-SEM methods. It was observed that topographic measurements were not significantly affected by the gold coating at tested scale. Moreover, changes on SEM setup leads to nonlinear outcome on texture parameters, such as fractal dimension and entropy values. For VP-SEM or LV-SEM, fractal dimension and entropy values did not present any evident relation with image quality parameters, but the resolution must be optimized with imaging setup, accompanied by charge neutralization.

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

“…Nevertheless the SEM has several limitations [11,12,13]: costly operation, electron beam-induced damage, vacuum degradation, charging effects, sputter-coating artifacts. Similarly, the use of atomic force microscopy, in spite of the large resolution and directly providing 3D images, usually covers very small and shallow areas.…”

The Effect of Hybridisation on Mechanical Properties and Water Absorption Behaviour of Woven Jute/Ramie Reinforced Epoxy Composites

“…It has a tungsten hairpin thermionic electron gun and can function from a low vacuum (5 Pa) to high chamber pressures of up to 3000 Pa in either a water vapor or nitrogen atmosphere (air). The secondary electron (SE) detector and the backscattered electron (BSE) detector are utilized with a working distance of 10 mm (at Analytical Working Distance) [ 35 ]. The specimens were sputter-coated with a thin layer of palladium and placed on the SEM holder through double-sided electrically conducting carbon adhesive tapes to avoid surface charge when exposed to the electron beam on the specimens.…”

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

“…The SEM stage was then calibrated with the Zeiss AxioVision 4.8 "Shuttle & Find" module by finding the reference marks, at low-voltage mode. The optimum level of beam energy (0.9 keV in this case) was defined according to the procedure developed by Hein et al (2013c) for the carbon-epoxy composite finding the optimum imaging condition for the range from 0.7 to 1.2 keV, as the boundary values for E 2 crossover secondary electron energies. Long fiber carbon-epoxy composites have heterogeneous properties of electric conductivity, where the conductive carbon fibers redistribute the charge carriers, whereas the insulator character of the epoxy resin sustains the charge imbalance, acting as a floating conductor (Craven et al, 2002).…”

“…Finally, the correlative light-electron fractography method (Hein et al, 2013 a , 2013 b ) presented here combines, pixel by pixel, the quantitative topography and contrast information provided by LMs to the fine lateral resolution from SEMs. It should permit translation of well-known fracture features from SEM images to those with LMs, paving the path for new development for fracture investigation of polymer composites.…”