High-Energy Ion Implantation of Polymeric Fibers for Modification of Reinforcement-Matrix Adhesion

The effet is considered of high-energy ion irradiation of ultrahigh molecular weight polyethylene (UHMW-PE), and Kevlar-49 polyaramid fibers, on fiber/matrix adhesion and interfacial shear strength (ISS) in epoxy matrix composites. Irradiation of UHMW-PE fibers produces large improvements in ISS, without degrading fiber tensile strength. ISS is not generally affected in irradiated Kevlar-49, and fiber tensile strength decreases. The divergence in response between polyaramid and polyethylene relates both to differences in the mesoscopic structure of the individual fibers, and to the different forms of beam induced structural modification favored by the individual polymer chemistries. Surface energy measurements, infrared spectroscopy analysis, and X-ray photoelectron spectroscopy studies have been performed on UHMW-PE and polyaramid fibers, irradiated to fluences between 2 x 10 exp 12 and 5 x 10 exp 15 cm exp --2 with N exp + , Ar exp + , Ti exp + , Na exp + , and He exp + at energies 30-400 keV. UHMW-PE fibers showed a pronounced increase in the polar component of surface energy which could be associated with carbonyl, hydroxyl, and hydroperoxide groups at the surface. Kevlar, on the other hand, tended toward carbonization and showed a decrease in nitrogen and oxygen concentrations and a sharp drop in polar surface energy.