On the Identification and Validation of an Anisotropic Damage Model Using Full-field Measurements

Abstract

Two different mechanical tests are performed on a laminated composite coupon to induce an anisotropic damage affecting essentially shear modulus softening. The first test is a uniaxial tension loading on a straight coupon, which is used to evaluate the damage law using a conventional approach, while the second contains a notch that enhances dramatically the strain (and hence damage) heterogeneity. A global digital image correlation approach is used to quantify the kinematic fields all along the loading path of the second experiment. Displacement fields are hence evaluated based on a finite element type discretization. A further exploitation based on the reconditioned equilibrium gap method (and without any further information) gives access to a quantitative measurement of the damage law. The latter approach makes use of a finite element model based on the very same mesh and element shape function. This full-field-based identification method compares very well with traditional techniques, up to the stage where macroscopic localization prevents their subsequent exploitations. Moreover, it is shown that neither the type of mechanical test, nor the discretization of the displacement field, affects the identification of the damage law.

Evaluating Damage with Digital Image Correlation: C. Applications to Composite Materials

“…For the last considered cycle (#14), a localized damage pattern is observed with a value of D approaching 1. This is in good accordance with the experimental failure pattern (Ben Azzouna et al 2011). The best solution is obtained with only one parameter e c1 for which c 1 is therefore close to 1.…”

“…Only the last of 14 loading/unloading cycles is shown herein. More results can be found in (Ben Azzouna et al 2011).…”

Direct identification of nonlinear damage behavior of composite materials using the constitutive equation gap method

“…(25). The resolution requires the calculation of the direction and the step of the descent using the gradient and the Hessian matrix of function Φ n ðpÞ.…”

“…There are five main techniques likely to be used to solve the identification problem: the virtual field method [3,[13][14][15][16], the FE model updating method [17][18][19][20][21], the reciprocity gap method [22,23], the equilibrium gap method [24,25], and the constitutive equation gap (CEG) method [26][27][28][29]. A review of these techniques is presented in [30] with a focus on noisy data in [5].…”

Enhanced features of a constitutive equation gap identification method for heterogeneous elastoplastic behaviours

“…digital image correlation, interferometric techniques, grid methods, etc. ): the finite element model updating method (FEMU) [1][2][3][4], the reciprocity gap method (RGM) [5,6], the constitutive equation gap method (CEGM) [7][8][9], the virtual field method (VFM) [10][11][12][13][14][15][16][17][18] and the equilibrium gap method (EGM) [19,20]. An overview of these identification procedures and their applications on experimental data can be found in [21].…”