In order to connect different components of the imperfections with structural features and their effect on shell buckling strength, the imperfections are generally decomposed using Fourier series.

In this paper numerical simulation was used on investigating the matrix yielding initiation and expansion of polymer blends which has a continuous single phase and a regular particles shape.

In the double yield surface model proposed by Lade, the projection of shear yield surface and that of volume collapse yield surface are significantly different on π plane.

An equation of the critical volume fraction, fpc, of particle-reinforcement in a composite, including particle size, yield strength of the matrix, dissipation work in the vicinity of the particles and the width of the interface zone, has been educed by the energy theory on the basis of the types of microscopic failure of the composite.