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Scanning Electron Microscopy

Upon completion of mechanical testing, the failed samples were returned to their humidity chambers. A representative sample of each board type from each humidity and from both three point bend and tensile tests was to be analysed using a Scanning Electron Microscope (SEM) (Figure ). The procedure for observing the the specimens was:

• The samples were held at their appropriate humidity for as long as possible. Fracture surfaces were preserved
• A match head sized () was taken from the fracture surface using a scalpel
• The samples were mounted on aluminium tabs with a conductive varnish
• The tabs were coated with gold, using a sputter coating procces. This ensures conductivity between the fracture surface, the aluminium tab, the electron beam and the imaging software. Due to the 'furry' nature of some of the samples the gold coating had to be done twice
• Samples were then loaded into the SEM. Comparisons of the fracture surfaces were made between the samples from different humidities, board types and failure mechanisms.

  
Figure: The SEM used to analyse the fracture surfaces of the board samples. The actual electron chamber is in the left background.