Aerodynamic and Morphological Properties of Carbon-Fiber Aerosols

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Abstract
Aerodynamic size analysis and electron microscope studies of the carbon-fiber aerosol particles generated in cutting and grinding virgin carbon fibers and their laminates showed the presence of a significant quantity of respirable, fiberlike particulates, presumably caused by fiber splitting. The mass median aerodynamic diameter (MMAD) of the fiber particles, sampled from a point 10 cm above the workpiece, was 4.0 μm, which was considerably smaller than the geometric diameter (7–8 μm) of the original individual fibers. The microscopic analysis showed that small quantities of fiber fragments had sharp edges, possibly resulting from splitting of the fibers during the machining process. The resin binders when exposed to temperatures of above 400°C vaporized and generated condensation aerosol particles in the accumulation mode with an MMAD of 0.77 μm. The carbon fibers when exposed to temperatures of above 850°C began to oxidize, which resulted in diminished diameters and significant changes in their structural properties. The change in structure was first apparent after 30 min and became substantial after 4 1/2 hr, when the data were taken. Debris generated in this process from carbon fibers consists primarily of amorphous carbon particles rather than fiberlike particles.

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