A two-level optimization procedure for material characterization of composites using two symmetric angle-ply beams

Abstract

A two-level optimization procedure for determining elastic constants E-1, E-2, G(12), and v(12) of laminated composite materials using measured axial and lateral strains of two symmetric angle-ply beams with different fiber angles subjected to three-point-bending testing is presented. In the first-level optimization process, the theoretically and experimentally predicted axial and lateral strains of a [(45 degrees/-45 degrees)(6)](s) beam are used to construct the strain discrepancy function which is a measure of the sum of the squared differences between the experimental and theoretical predictions of the axial and lateral strains. The identification of the material constants is then formulated as a constrained minimization problem in which the best estimates of shear modulus and Poisson's ratio of the beam are determined to make the strain discrepancy function a global minimum. In the second-level optimization process, shear modulus and Poisson's ratio determined in the first level of optimization are kept constant and Young's moduli of the second angle-ply beam with fiber angles different from 45 degrees are identified by minimizing the strain discrepancy function established t this level of optimization. The suitability of the proposed procedure for material characterization of composite materials has been demonstrated by means of a number of examples. (c) 2007 Elsevier Ltd. All rights reserved.