Micromechanics of a model heterogeneous material system under compressive loading

Abstract

Compressive loading is often encountered in mining and mineral processes during the comminution of ore bearing minerals, or alternatively, in the wear-resistant materials used in the comminution circuit. A common thread joining many of the engineered materials used predominantly under compressive loading is the presence of a high modulus secondary phase, either fiber or particulate, embedded within a lower modulus matrix phase (i.e., a brittle heterogeneous material). To improve their toughness, an imperfect or a less-than-coherent interface is often strived for in the manufacture of many heterogeneous materials. To better understand the complex behavior of these materials, a model heterogeneous material system was developed by the U.S. Bureau of Mines and the Idaho National Engineering Laboratory. In this work, moire interferometry was used to map the micromechanical displacements on the surface of the model system. Uniaxial and biaxial compressive loading was applied to a model system consisting of a PMMA (polymethylmethacrylate) plate having a precision ground steel rod as the cylindrical reinforcement. Moire patterns revealed that two dominant phenomena occur along the interface: (1) frictional slip/stick and (2) a form of semi-cohesive bonding or mechanical locking. These observations were subsequently confirmed by nonlinear finite-element simulations of the model heterogeneous system. Experimental and numerical results show that the imperfect interface plays an important role in the micromechanical behavior of these model systems.