Mode II fracture behaviour of PET modified brittle epoxies

Mode II Fracture behaviour of PET modified epoxy systems are studied in comparison with that of mode I. For mode II fracture, single edge notched specimens were used under skew symmetric four-point loading. The mode II fracture toughness obtained for modified systems has been found to increase significantly over the control whereas the increase of mode I fracture toughness for modified systems over the control is moderate. This finding is discussed in relation with cavitation and equivalent mode I stress intensity factor and also in comparison with rubber modified epoxy systems in the literature to account for the increase. In addition, difference in morphology of fracture surfaces between mode I and II is discussed.