The 3-D effective properties module provides a “Convergence study” that determines the 9 independent orthotropic properties for typical elements composed of composite materials. It has been found that the bending properties of a composite laminate are functions of thickness of the laminate up to a particular threshold thickness. The study of how the properties converge to a particular value and after that it does not change by changing the thickness of the laminate, can be performed using this module. The result has important implications in case of FEM analysis of composite laminates. If one wants to use the converged effective engineering properties of a sub-laminate in the FEM analysis, the size of the element chosen to analyze a particular laminate has to be greater than the threshold thickness of that sub-laminate. If the element size is less than the threshold thickness then for every new element size, one has to find the effective properties for that particular thickness. However, it is found that the threshold thickness of a sub-laminate normally composed of a few repeating laminae is less than typical element sizes used in finite element analysis of automobile structures.

For example, users of the software will input the ply (or lamina) properties, ply thickness, and ply orientation for all plies (laminae) within the laminate. The program will then provide the users with the 3-D effective orthotropic homogeneous properties of the composite laminate. Also, the program will provide the threshold thickness if the “Convergence Study” is included in the analysis. These converged effective properties can then be used as inputs into the DYNA3D or any other finite element analysis software.

Note: For a thick composite structure that made up of the sublaminates, the minimum thickness (for elements) should not be below the threshold thickness, to use the same effective properties as the size of elements are varied in the FEA design process.