Formation and Growth of Cracks in 7075-T6 Aluminium Matrix Hybrid FML Nanocomposite Materials

Abstract

The paper scopes on the experimental data, computer and theoretical (analytical) models of the crack formation processes in hybrid nanocrystalline materials with nanoparticle filler of 7075-T6 aluminium matrix under the influence of high-speed and quasi-static deformation regimes. Presenting the main experimental facts and results of the computer modelling, particular attention is paid to the theoretical models describing the formation of nanoscopic cracks in the tips of the microcracks in hybrid nanocrystalline materials at high speeds and quasi-static deformation. A model describing the formation and growth of nanocracks near the tips of the blunt cracks in a hybrid nanocomposite material is proposed. Within the model, the concentration of stresses at the tips of the blunt cracks causes the grain boundaries to slip and dislocations at the grain boundary junctions. The stresses, which create these dislocations, and the load applied to the crack peaks cause the nanocracks to form and grow. As shown, an increase in the radius of curvature at the tips of a thick crack and a decrease of the grains’ size contribute to the growth of nanocracks. These trends are consistent with experimental data on the low decomposition viscosity and high plasticity of the most nanocrystalline materials.

Keywords

• fibre metal laminate (fml)
• hybrid fml nanocomposite
• elliptical crack
• viscous collapse
• tension
• plasticity