IMPROVE GRAPHITE/EPOXY COMPOSITES

HIGH STRENGTH CARBON-FIBER COMPOSITE MATERIALS CONTINUE TO HAVE A MAJOR LIMITATION IN THE WEEK BONDING ACHIEVED BETWEENTHE FIBER AND THE MATRIX. THE RESULTS ARE LOW INTERLAMINAR SHEAR STRENGTH AND LOW TRANSVERSE TENSILE STRENGTH OF THE FIBER. OXIDATIVE ETCHINGS AND COATINGS HAVE PROVEN MOST EFFECTIVE IN IMPROVING THE BOND STRENGTH, BUT THE EXTENT TO WHICH PRIMARY CHEMICAL BONDS HAVE BEEN ACHIEVED REMAINS QUESTIONABLE. THE TREND TO HIGHER PERFORMANCE GRAPHITE FIBERS AGGRAVATES THE BONDING PROBLEM. SURFACE CHEMICAL MODIFICATION OF POLYARAMID FILAMENTS, INDUCED BY GLOW DISCHARGE PLASMA TREATING, HAS BEEN HIGHLY EFFECTIVE IN MODIFYING THE SURFACE ENERGETICS TO ENHANCE WETTING AND DEPOSITING REACTIVE GROUPS WHICH CAN FORM COVALENT BONDS WITH THE RESIN. THE RESULT HAS BEEN A SIGNIFICANT IMPROVEMENT IN OFF-AXIS PROPERTIES OF KEVLAR/EPOXY COMPOSITES. THE FEASIBILITY OF MODIFYING THE SURFACE CHEMISTRY OF GRAPHIC FIBERS WITH GLOW DISCHARGE PLASMA TREATMENT PROCESS TO INCREASE CHEMICAL BONDS WITH RESINS WILL BE INVESTIGATED.TWO CARBON FIBERS AND TWO EPOXY RESINS WILL BE STUDIED WITH AMMONIA AS THE SOURCE GAS. FIBER CHARACTERIZATION TESTS WILL BE CONDUCTED ALONG WITH MECHANICAL TESTING OF GRAPHITE/EPOXY SPECIMENS.