Damage Quantification in Metal Matrix Composites

An experimental procedure is presented to quantify damage in terms of microcrack density. This is accomplished by experimentally evaluating the components of a second-order damage tensor for a metal matrix composite material. The procedure involves the use of a scanning electron microscope and image analyzing software to quantify physical damage features found on a representative volume element. These features are quantified in terms of crack density, which is used in developing the second-order damage tensor. The procedure could be applied to voids in a similar fashion. This procedure is applied to the following two different balanced symmetric layups: (1) (0/90)S; and (2) (±45)S. Uniaxial tensile loads are used to induce damage in test specimens for each of the layups. Damage evolution is obtained by loading specimens over a range of load intensities from rupture load down to 70% rupture load. A good comparison is obtained between experimentally evaluated and numerically calculated damage values. A companion paper by Voyiadjis and Deliktas used the experimental data presented here in order to verify their proposed formulation for a coupled anisotropic damage model for the inelastic response of composite materials. A physical interpretation of the second-order damage tensor, ;qf, is presented in their work.