Impact Response of Sandwich Beams with Functionally Graded Core

Abstract

The problem of low-speed impact between a rigid cylindrical indentor and a sandwich beam with functionally graded core is solved. The problem is a combination of the static contact problem and the dynamic response of the sandwich panel obtained via a simple spring-mass model. The variation of core Young's modulus is represented by a polynomial in the thickness coordinate, but the Poisson's ratio is kept constant. The two-dimensional elasticity equations for a sandwich structure with functionally graded core subjected to transverse loads are solved using a combination of Fourier analysis and Galerkin method. The contact problem is solved using the assumed contact stress distribution method. For the impact problem we used a simple dynamic model: the sandwich beam was modeled as a combination of two springs, a linear spring to account for the global deflection and a nonlinear spring to represent the local indentation effects. Results indicate that the contact stiffness of the beam with FG core increases causing the contact stresses and other stress components in the vicinity of contact to increase. However, the values of maximum strains corresponding to the maximum impact load are reduced considerably due to grading of the core properties. For a better comparison, the core thicknesses of FG cores were chosen such that the flexural stiffness of the sandwich beam will be equal to flexural stiffness of the beam with homogeneous core. The results indicate that functionally graded cores can be used effectively to mitigate or completely prevent impact damage in sandwich composites.