EFFECT OF FLUX TEMPERATURE ON DUAL RESIN BOND PERFORMANCE

Dual resin bonding of thermoplastic matrix advanced composite componen ts has been developed in an attempt to overcome many of the inherent p roblems encountered when using conventional adhesives or fusion bondin g approaches. The dual resin bonding process makes use of a second mis cible polymer to ''flux'' the composite surface and allow joining to b e accomplished at temperatures lower than the distortion temperature o f the matrix material. This approach minimizes she need for special to oling and facilitates reproducible, high performance joints which requ ire minimal surface preparation and can be performed in the field with out damaging the composite structure. PEI is the polymer used in combi nation with PEEK in much of the work to date on dual resin bonding. Th e common approach to processing PEEK/PEI involves applying the ''flux' ' PEI at 380 degrees C, the process temperature of the PEEK matrix. Th is allows the ''flux'' to be applied in a coprocessing operation durin g composite consolidation. Final joining is then accomplished at a sub stantially lower temperature, near 300 degrees C. While using the PEEK processing temperature is convenient, it may not be the optimal proce ss condition for maximum joint performance. This work investigates the effect of variation in the ''flux'' stage processing temperature. Sin gle lap shear testing was performed on dual resin bonded carbon fiber reinforced PEEK composite joints fabricated with ''flux'' temperatures ranging from 310 degrees C to 425 degrees C. The resulting joint perf ormance was relatively uniform for samples processed from 330 degrees C to 390 degrees C for tests at both room temperature and 150 degrees C. However, based on failure mode investigations and preliminary FTIR studies, a ''flux'' temperature of approximately 340 degrees C, which is lower than that currently used, has the potential to yield the high est single lap shear values. Thus, this work suggests that, based on d etails of the polymer blend formation, consideration be given to the u se of modified ''flux'' temperatures to attain the maximum performance from dual resin processes.