Surface Damage Modeling of Oxidized Metal Matrix Composite Laminates under Axial and Transverse Tension

The oxidation effects on surface crack development of oxidized Ti-15-3 and fl-21S Metal Matrix Composite (MMC) unidirectional laminates under applied axial or transverse tension loadings are investigated in the present study. An approximate mechanical model is established and a stress analysis of an oxidized laminate with surface cracks is performed. To simplify the analysis, motivated by experimental observations, a periodic distribution of surface cracks in the oxide layer is assumed. The critical value of the applied mechanical load, which is necessary for the information of new cracks as a function of crack density, is calculated for given oxide layer thickness. The effective stiffness reduction, caused by the formation of the surface cracks, is also evaluated. Finally, the influence of gradient effective properties of the metal matrix underneath the oxide layer, caused by the diffusion of oxygen, on the stress field is considered.