M. Schmiicker et al /Composites: Part A 34(2003)613-622 to the European Prestandard ENV 658/5 to be 3L/(4bh) with L= load, b= sample width and h= sample height e 2. 4. Microscopy and image processing Prior to ceramography the porous WHIPOX material was infiltrated with low-viscous epoxy resin. Subsequently, the samples were cut into 1.5-2.0 mm thick slices and prepared for optical inspections by grinding and polishing with standard methods For the microscopic analysis, an optical microscope was used in the transmission mode with low magnification (50 X). This method has the advantage that Fig 3. Optical micrographs of WHIPOX taken in reflection (left) and the fibers'light transmission produces a strong contrast, ansmission mode (right), respectively. The fibers' light conductivity making fibers appear bright and larger fiber free areas dark yields very high contrasts in the transmission mode (Fig. 3), thus facilitating semi-automatic image processing Microscopy ss an contrast reduce size to30% Assemble pictures of one slice Further adjust brightness and contrast Apply Gaussian Blur Change colour mode to black and white Analysis with “ Scion Image Fig. 4. Flow chart showing steps of image processing and analysis.to the European Prestandard ENV 658/5 to be 3L=ð4bhÞ with L ¼ load, b ¼ sample width and h ¼ sample height. 2.4. Microscopy and image processing Prior to ceramography the porous WHIPOX material was infiltrated with low-viscous epoxy resin. Subsequently, the samples were cut into 1.5–2.0 mm thick slices and prepared for optical inspections by grinding and polishing with standard methods. For the microscopic analysis, an optical microscope was used in the transmission mode with low magnification (50 £ ). This method has the advantage that the fibers’ light transmission produces a strong contrast, making fibers appear bright and larger fiber free areas dark (Fig. 3), thus facilitating semi-automatic image processing. Fig. 3. Optical micrographs of WHIPOX taken in reflection (left) and transmission mode (right), respectively. The fibers’ light conductivity yields very high contrasts in the transmission mode. Fig. 4. Flow chart showing steps of image processing and analysis. M. Schmu¨cker et al. / Composites: Part A 34 (2003) 613–622 615