THE DEVELOPMENT OF A CONTROLLED INTERFACIAL BOND STRENGTH PROCESS FOR CARBON-PHENOLIC AND CARBON-CARBON COMPOSITES

CARBON/PHENOLIC COMPOSITES SUFFER FROM LOW INTERFACIAL BOND STRENGTHS, THE RESULT OF POOR SECONDARY BONDING AND THE FAILURE TO DEVELOP COVALENT BONDS AT THE FIBER-MATRIX INTERFACE. THE CONSEQUENCES ARE A COMPOSITE MATERIAL SYSTEM WITH MAJOR LIMITATIONS DUE TO LOW INTERFACIAL SHEAR AND TRANSVERSE TENSILE STRENGTHS. THE CONVERSION OF CARBON/PHENOLIC INTO A CARBON/CARBON MATERIAL FURTHER REDUCES INTERFACIAL BOND STRENGTHS. THIS LIMITS THE STRUCTURAL USAGES OF CARBON/CARBON BECAUSE OF VERY LOW OFF-AXIS MECHANICAL PROPERTIES. PLASMA TREATMENT PROCESSES UTILIZING AMMONIA AS A SOURCE GAS HAVE DEMONSTRATED THE CAPABILITY OF ESTABLISHING REACTIVE AMINE GROUPS ON ARAMID AND CARBON FIBERS WHICH CAN FORM COVALENT BONDS WITH EPOXY RESINS. MECHANICAL TESTING OF THE PLASMA-TREATED ARAMID/EPOXY COMPOSITES HAVE DEMONSTRATED MAJOR INCREASES IN OFF-AXIS MECHANICAL PROPERTIES AND RESISTANCE TO MOISTURE ABSORPTION, CONFIRMING THE STRENGTHENING OF INTERFACIAL BONDS. THE FEASIBILITY OF IMPROVING THE INTERFACIAL BOND STRENGTH OF A CARBON/PHENOLIC COMPOSITE THROUGH A PLASMA TREATMENT PROCESS WILL BE INVESTIGATED. WATER VAPOR WILL BE THE PLASMA SOURCE GAS TO PROVIDE HYDROXYLS FOR SURFACE DEPOSITION ON THE CARBON FIBERS. THE ABILITY TO CONTROL THE HYDROXYL GROUP CONCENTRATION AS A FUNCTION OF PLASMA TREATMENT CONDITION WILL BE INVESTIGATED. MECHANICAL TESTING OF COMPOSITES AND FRACTURE SURFACE MORPHOLOGY STUDIES WILL INDICATE THE DEGREE OF COVALENT BONDING ATTAINED. MAINTENANCE OF THE COVALENT BONDING THROUGH A CARBON/PHENOLIC CARBONIZATION CYCLE WILL ALSO BE ADDRESSEDVIA MECHANICAL TESTING.