MEASUREMENT OF THE FRACTURE ENERGY OF INTERFACES IN COMPOSITES THROUGH SANDWICH-TYPE CHEVRON-NOTCHED SPECIMENS

A sandwich-type chevron-notched specimen with a phase angle of loading near zero has been proposed to measure the fracture energy of interfa ces arising mainly From chemical bonding. With the specimen configurat ion of this kind, the advantages from both sandwich test specimens and chevron-notched specimens can be combined to provide an easy and accu rate test for the measurement of the interfacial fracture energy. The validity of the specimen has been analyzed in terms of the mechanics o f sandwich-type specimens and chevron-notched specimens, and demonstra ted using the Al2O3/Nb bimaterial system. The results show that for a phase angle of loading around -7 degrees the Al2O3/Nb interface has a fracture energy of 9.3 +/- 0.2 J/m(2) that changes to 16.8 +/- 1.1 J/m (2) when Nh is preoxidized before the formation of the Al2O3/Nb interf ace.