Subcritical Crack Growth along Ceramic‐Metal Interfaces

Environmentally assisted subcritical crack growth along glass/copper interfaces is examined in ambient‐temperature gas environments as a function of humidity. Resulting interfacial crack velocities (v), characterised in terms of the crack extension force (G) and approximate solutions for the linear elastic stress intensity factor (K), show ν‐K curve behavior typical of (bulk) ceramics. Subcritical crack growth rates are found to be initially highly sensitive to K for G) and to show evidence of a threshold stress intensity between 0.1 and 0.25 Mp a°m 1/2 (region I). At higher crack velocities typically between °10 –5 and 10 –4 m/s, growth rates display a plateau and tend to become K independent (region II). Although specimen‐to‐specimen scatter is large in region I, interfacial crack velocities in moist environments far exceed those in dry environments and are over 3 orders of magnitude faster (at fixed K) than reported rat's for (bulk) soda‐lime glass.