Crack initiation in brittle solids under multiaxial compression

Experiments combined with numerical simulations were used to study crack initiation in brittle materials under biaxial static compression with particular attention to the frictional resistance of the cracks. A new methodology has been developed to prepare specimens with a central crack where crack surfaces are in contact and with the desired friction coefficient: two pieces of Homalite-100 (a brittle polymer) were bonded except for a central region that served as a crack. The measured failure load for cracks with different orientation angles and surface roughness was in close agreement with theoretical predictions for compressive failure. In situ photoelastic fringes were obtained and compared with numerical results enabling the determination of stress distribution along crack faces, as well as the identification of slip and stick regions.