Genetic evolution of nonlinear material constitutive models

Material constitutive model is highly nonlinear and multimodal in the large parameter space. A genetic evolution algorithm is thus proposed for its recognition. The nonlinear stress-strain relationship presented by several added multinomials, whose structure is not simplified, is automatically recognized from global response information, e.g., load vs. reflection data, obtained from a structure test through genetic evolution in global space. Nonlinear finite element analysis is used as a bridge to build a relationship between stress-strain data and load-deflection information. The potential of the proposed method is demonstrated by applying it to the macromechanical modeling of nonlinear behavior in advanced composite materials. A nonlinear material model for the ply is recognized using experimental results on a lamina plate [(+/- 45)(6)](s) to be a modification of Hahn-Tsai model [H.T. Hahn, S.W. Tsai, J. Compos. Mater. (1973) (7) 102]. The obtained nonlinear constitutive model is subsequently used to predict nonlinear behaviors of the [(+/- 30)(6)](s) and [(0/45)(4)](s) plates. The results are satisfying. This modeling procedure can be used as a method to guide to improve analysis of nonlinear behavior and damage of composite materials. (C) 2001 Elsevier Science B.V. All rights reserved.