Abstract
Unidirecitonal pre-preg carbon fibers of ten peel plies were laid up at 0-, 45-, -45-, and 45-degree stacking sequences on a flat and smooth aluminum (Al) plate, and then carbonized electrospun polyacrylonitrile (PAN) nanofibers were placed on top of the last ply prior to vacuum curing in a vacuum oven. The PAN electrospun fibers were oxidized at 280 degrees C in an ambient condition for 1 hr and then carbonized at 850 degrees C for 1 hr in an argon (Ar) gas atmosphere. The resultant composite panels were cut into small pieces and subjected to a number of different characterization techniques. Thermal mechanical analysis (TMA) measurements clearly showed that significant reinforcement was achieved for the pre-preg/carbonized PAN fiber composites because of the enhanced interfacial bonding between the PAN nanofibers and the matrix. Dynamic mechanical analysis (DMA) tests exhibited a shift of the glass transition temperature of the carbonized PAN nanofiber/composite, which may be helpful for high-temperature applications of the present composites. A Raman spectroscopy peak around 897 cm(-1) indicated formation of the gamma-phase of the carbonized PAN fibers. The highest stretching peak of the CH2 group was recognized within the range of 2,500-2,800 cm(-1) for the carbonized fibers. The vibration peak of the C N group also appeared at 1,452 cm(-1) spectrum. TMA determined the coefficient of thermal expansion (CTE), indicating an improvement in stability of the composite material, which can be useful for structural health monitoring (SHM) as well as lightning strikes and electromagnetic interference shielding applications of new carbon fiber composites.