Modal analysis of an aluminum beam coated with damaged and porous functionally graded material.

In this paper modal analysis is performed on a symmetric aluminum beam which is coated with functionally graded material containing porosities. A polynomial function is used to vary the density and elasticity through the thickness of the coating, while the effective elastic modulus and density are found with classical lamination theory. To achieve a truthful modeling the gradually changing mechanical properties of the coating are modeled as 25 layers of material, while each individual layer is isotropic and homogeneous. MATLAB is used to write a finite element code and Timoshenko beam elements are used to include shear deformation effects. To show the influences of crack location, crack depth, porosity and the polynomial function index on the natural beam frequencies a parametric study is conducted. Multiple boundary conditions were also considered and it was found that the natural frequency values were significantly affected by the studied parameters. [ABSTRACT FROM AUTHOR]