Analysis of mode II fractured surfaces of graphite/epoxy laminates using SEM and optical reflectivity methods.

This paper presents a study of scanning electron microscope surface morphology and the reflectivity of the mode II fractured surface of graphite/epoxy laminates. A discrete number average method was developed for the quantitative characterization of hackles formation. The variation of hackle marks linear density with impact energy for end-notch flexure and centre-notch flexure for pure mode II loading were determined. The results indicated that hackles formation decreased with impact energy and the maximum hackles formation were observed at the centre area. Reflectivity was observed to be increased with the angle of reflection and decreased with impact energy, which is in agreement with the scanning electron microscope analysis. With the incident light scanned in the transverse direction, the intensity of the reflected light increases much more exponentially compared with along the fibre direction. Reflectivity in the fibre direction was clearly lower than in the transverse direction in the damaged area. The greater the damaged area, the less the intensity (reflectivity) of light reflected. [ABSTRACT FROM AUTHOR]