Abstract
In an interlayered carbon fiber reinforced polycarbonate (CFRPC) composite constructed of nine CF plies alternating between ten PC sheets, designated [PC](10)[CF](9), applying homogeneous low voltage electron beam irradiation (HLEBI) at 200 kV cathode potential, with V(c) setting at a 43.2 kGy dose, to both finished sample surfaces resulted in a 47% increase in Charpy impact strength and a(uc) at median fracture probability (P(f)) of 0.50 over that of untreated, from 118 kJm(-2) to 173 kJm(-2). Increasingly higher V(c) settings of 150, 175, and 200 kV successively increased a(uc) at median-P(f) of 0.50 to 128, 155, and 173 kJm(-2), respectively. Strengthening is attributed to increasing the HLEBI penetration depth, D(th), into the sample thickness. Since the [PC](10)[CF](9) has an inhomogeneous structure, D(th) is calculated for each ply successively into the thickness. Scanning electron microscopy (SEM) photos showed a hierarchy of fracture mechanisms from poor PC/CF adhesion in untreated; to sporadic PC adhesion with aggregated CF at 150 kV; to high consolidation of CFs by PC at 200 kV. X-ray photoelectron spectroscopy (XPS) examination of the CF surface in the fracture area showed C1s carbonate O-(C=O)-O and ester O-(C=O)-R peak generation at 289 to 292 eV to be non-existent in untreated; well-defined at 150 kV; and increased in intensity at 200 kV, after which a reduction was observed at 225 kV. Moreover, the 200 kV yielded the largest area sp(3) peak at 49.5%, signifying an increase in graphitic edge planes in the CF, apparently as dangling bonds, for increased adhesion sites to PC. For O1s scan, 200 kV yielded the largest area O-(C=O)-O peak at 34%, indicating maximum PC adhesion to CF. At the higher 225 kV, increase in a(uc) at P(f) of 0.50 was less, to 149 kJm(-2), and XPS indicated a lower amount of O-(C=O)-O groups, apparently by excess bond severing by the higher V(c) setting.