Separation at the Interface of a Circular Inclusion and the Surrounding Medium Under an Incident Compressive Wave

Abstract

Separation at the interface of a circular inclusion embedded in a matrix of lower characteristic impedance and subjected to incident compressive waves is investigated, both experimentally and analytically. In the experiment, the compressive waves were generated by small explosive charges. For small charges, separation was not observed. As the explosive charge was increased, separation was observed at the “shadow side” of the inclusion. For still higher charges, separation was observed at the front face as well as at the shadow side of the inclusion. The qualitative analytical treatment is based on the methods of propagating stress discontinuities. It is shown that a compressive stress wave is converted into a tensile wave after a refraction and a reflection inside the inclusion. The reflected discontinuity of the tensile stress at the wave front is magnified upon passage through a focal point before reaching the shadow side of the inclusion. A divergence factor in conjunction with the closer proximity of the caustic to the back face reduces the level of tensile stresses reaching the front face. Separation is thus less likely to occur at the front face, which was verified experimentally. The results of this paper apply to the behavior of fiber-reinforced composites under dynamic loading conditions.