This paper describes experimental observations of various phenomena charact
eristic of dynamic intersonic decohesion of bimaterial interfaces. Two sepa
rate but complementary optical methods are used in conjunction with high-sp
eed photography to explore the nature of the large-scale contact and mach w
ave formation at the vicinity of running cracks in two different bimaterial
systems. Theoretical predictions of crack tip speed regimes, where large-s
cale contact is implied, are confirmed. Also, the theoretically predicted m
ach wave emanating from the intersonically propagating crack tip is observe
d. Direct visual evidence is also obtained for another traveling mach wave
emanating from the end of the intersonically moving contact zone. Subsequen
tly, a physical model for intersonic crack propagation along bimaterial int
erfaces is presented and ratified in view of recent experimental observatio
ns and theoretical developments. Finally, the paper presents very recent ex
perimental evidence that shows crack tip speeds exceeding the intersonic re
gime and becoming clearly supersonic. (C) 1998 Elsevier Science Ltd. All ri
ghts reserved.