Analysis of Strain Field Heterogeneity at the Microstructure Level and Inverse Identification of Composite Constituents by Means of Digital Image Correlation.

Witold Ogierman,Grzegorz Kokot

doi:10.3390/ma13020287

Abstract

The present paper is devoted to the theoretical study on the estimation of the full-field strain at the microstructural level of composite materials by means of Digital Image Correlation (DIC). The main aim of the paper is to investigate the influence of speckle size on the accuracy of the strain field measurement at the microscale. The DIC analysis was conducted based on artificial speckle patterns generated numerically and the deformation behavior of the composites was simulated by using the finite element method (FEM). This approach gives the opportunity to compare the results of the DIC in terms of speckle size with the reference FEM solution. Moreover, the paper focuses on the inverse identification of the material constants of the composite constituents by using information associated with the measured strain field. The inverse problem is solved by using a novel two-step optimization procedure, which reduces the problem complexity. The feasibility and accuracy of the proposed approach are presented by analysis of two exemplary microgeometries representing the microstructures of fiber reinforced composites.

Highlights

Effective mechanical properties of composite materials depend on the material properties of the constituents, the shape and volume fraction of the reinforcement as well as the interactions between the reinforcement and the matrix
Rahmani et al [32] used the full field measurement data for identification of the elastic constants of composite constituents, the authors improved the finite element model updating method by adding a regularization term which assumes that besides the displacements, the results provided by the micromechanical model are fitted to the experimental data
The present paper introduces a novel approach of inverse identification which is based on minimizing the discrepancy between the per phase average strains measured experimentally and computed by using finite element method (FEM)

Summary

Introduction

Effective mechanical properties of composite materials depend on the material properties of the constituents, the shape and volume fraction of the reinforcement as well as the interactions between the reinforcement and the matrix. The strain field at the microscopic level is inhomogeneous due to the contrast between the matrix and reinforcement material properties. The strain field heterogeneity can be analyzed by using various analytical, numerical and experimental methods. Analytical micromechanical models based on Eshelby’s solution [1] such as Mori–Tanaka [2,3] or self-consistent [4,5] methods allow the estimation of the strain partitioning between the matrix and reinforcement by referring to the per phase average strains. The most versatile and widely used numerical method for analysis of the deformation behavior of composites at the microstructural level is the finite element method (FEM) [6,7,8,9]. The other numerical methods which can be used for this purpose are the boundary element method (BEM) [10,11] and meshless methods [12,13]

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