TOUGHENING MECHANISMS IN MODIFIED EPOXY-RESINS WITH DIFFERENT CROSS-LINK DENSITIES

Crack-tip deformation has been investigated in pre-cracked samples of core-shell rubber particle modified epoxy resins with different degree s of crosslinking. Light cross linking resulted in cavitation of the m odifier, the formation of croids and extensive crack-tip yielding, whe reas these deformation mechanisms were suppressed at room T in highly crosslinked specimens. A zone of particle debonding was observed in th ese latter at high T, but this appeared detrimental to the toughness. Indeed it was possible to increase the toughness in this case by oxyge n plasma treatment of the modifier particles.