Abstract
The fiber/matrix interfacial strength of graphite fiber reinforced epoxy (DGEBF cured with diprimary amine (9,9-bis[3-methyl-4-aminophenyl]fluorene) has been studied to determine the effect of second phase additions of rubber and glass on the interfacial strength. Single fiber fragmentation tests, microindentation tests, single fiber push-out tests, and in-situ observations of fracture of specimens loaded in a SEM have been utilized. The single fiber fragmentation tests were not successful due to the failure of the single fiber test specimen prior to saturation in the fiber fragmentation process. The microindentation tests were also unsuccessful due to fracture in the carbon fiber prior to interfacial debond. The fiber push-out test results were twice as high as the shear strength of the resin, raising questions about what was really being measured and whether the 30% difference was significant on a relative scale. On the other hand, in-situ fracture observation in a scanning electron microscope (SEM) indicated that the initiation of damage, which occurred due to fiber/matrix debonding, occurred at similar ply stress levels in each of the four specimens. Furthermore, the propagation of such damage in all four systems studied seemed to pass along fiber/matrix interfaces only when it was convenient to the fracture path and not preferentially, again suggesting equally good interfaces in each of the four tests. In conclusion, it does not appear that the addition of rubber or glass second phase particles to this composite material has any significant effect on the interfacial strength of the composite system.
Lu, Chung-Yuan (1996). The effect of second phase particles in the fiber/matrix interfacial strength of carbon fiber reinforced thermoset composites. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -L8.