FRACTURE OF AN ELASTIC STRIP CONTAINING A PAIR OF COLLINEAR CRACKS PERPENDICULAR TO THE EDGES OF THE STRIP - THEORY AND EXPERIMENT

A theoretical and experimental study is made on the fracture of an infinitely long strip containing a pair of collinear cracks perpendicular to the edges of the strip. In the theoretical investigation, the surfaces of the cracks are loaded by an arbitrary opening pressure, while the edges of the strip are free from tractions. By the use of the Fourier transforms and the finite Hilbert transform, the problem is reduced to the solution of the Fredholm integral equations of the second kind. In the case of uniform opening pressure, the exact expressions for the stress intensity factors at the inner tip and the outer tip of the cracks and the shape of the deformed crack are derived. Numerical calculations are carried out to study the interaction between the cracks and the effect of the edge free boundary. A series of tensile tests of PMMA strips containing a pair of collinear cracks of equal length is carried out to study the correlation between the experimental data and the values predicted from the equations obtained in this investigation.