Degradation instabilities in brittle material structural systems

The paper focuses on energy based instability analysis of brittle material structural systems. In such structures, two types of degradation instabilities are possible. The first is due to surface degradation growth and results into spalling of layers at the stress-free surfaces. The second is due to damage progression, and results into globally unstable response of the structure. Simple problems are treated analytically, while more complicated ones are treated computationally. It is concluded that surface degradation instability and/or damage progression instability occurs before the peak strength is reached. Thus a homogeneous post peak material response may be impossible, since basic energy criteria are violated. Numerical results are presented and discussed in detail.