Numerical Analysis of Complex Composite Structures Using LISA: Local Interaction Simulation Approach

Student : Kalyan Nadella

Sponsor : NASA Constellation University Institutes Projects / Advanced Composites Technologies Program


A complete 3D-elasticity based formulation becomes extremely complicated for modeling sandwich structures because of the interface conditions and accounting the shape of the unit cells in the formulation and Traditional numerical tools such as FEM inefficient due to large computational cost associated with small wavelength discretizations. So, a numerical method is being implemented to model the composite structures.

Schematic diagram showing the discretization in a 1D LISA formulation. The black dots represent the nodes and the line between two dots represents a unit cell.


  • The LISA method is based on iterative equations (IE) for “unit cells” that are used to represent/discretize the model as shown in figure below.
  • The actual IEs are derived from the elastodynamic equilibrium equations. The coefficients in these iterative equations depend only on the local physical properties.
  • Continuity of displacements and stresses are enforced at the interface between the cells (sharp interface method). Therefore, changes in stiffness, density, or attenuation can be accounted for as the IE coefficients in adjacent cells with different properties will be different.
Time domain propagation of Hann-modulated toneburst in a structure made up of two materials with different physical properties.


  • Objectives of the project are to develop a working and robust 2-D and 3-D modeling to analyze guided wave propagation in complex composite structures like honeycomb composite structures.