Insert-molded poly(ether imide)/carbon fiber poly(ether ether ketone) bimaterial composites: Fracture and interfacial analysis



Bimaterial composites were constructed by injecting carbon-fiber-filled poly(etheretherketone) (CF PEEK) into a mold containing one-half of a poly(etherimide) (PEI) tensile specimen. Specimens were notched at the interface and tested in tension. Using fracture mechanics, the adhesion strength of the interface (a fracture energy with units of energy per area) was calculated from notch size and stress–strain behavior of the notched specimens. Fracture energies (with units of energy per area) of the PEI/CF PEEK bimaterial composites were slightly less than those measured from the monolithic materials of construction. Variations in test speed (below the glass transition temperature of the two components) had little effect on stiffness or fracture energy. However, fracture energies decreased slightly as temperature increased. Composites fractured through the CF PEEK near the PEI/CF PEEK interface. Consequently, the fracture surface of the PEI portion had a thin layer of CF PEEK (a qualitative indicator of good adhesion). Microscopy and X-ray photoelectron spectroscopy confirmed the presence of a thin layer of CF PEEK on the PEI. It appears that the miscibility of PEI and PEEK contributed to the strength of the PEI/CF PEEK thermophysical bond. The strength of the thermophysical bond of the PEI/CF PEEK bimaterial composites was greater than the cohesive strength of amorphous commodity polymers such as polystyrene and should be more than adequate for most microelectronics device handling applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:2362–2371, 2006