PSI - Issue 33

Daniele Gaetano et al. / Procedia Structural Integrity 33 (2021) 1042–1054 Author name / Structural Integrity Procedia 00 (2019) 000–000

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used in engineering applications, especially in aeronautical engineering for the construction of aircraft fuselages, by virtue of its excellent fatigue and fracture behavior (see for instance Hashagen and de Borst, 2000). The glass/epoxy pre-preg layer is characterized by a periodic microstructure with a hexagonal fiber arrangement, here assumed to preserve isotropy in the orthogonal plane to the fiber direction. Each fiber as a diameter of 10 μm and the fiber volume fraction is of 60%. It follows that the transverse homogenized response of this layer can be obtained, after choosing as RUC geometry that sketched in Fig. 4.

Fig. 4. Periodic microstructure of the glass/epoxy pre-preg layer and related Repeating Unit Cell (RUC).

As elastic property values of the different components of the GLARE TM composite system, those reported in Table 1 have been used for obtaining the present numerical results.

Table 1. Elastic properties of the GLARE TM components. Component Material

E (GPa)

ν (-) 0.37 0.23

Matrix

Epoxy Glass

3.90 86.9

Fiber

Metal layer

Aluminum

72

0.3

According to the procedure described in Section 3, firstly, the undamaged overall moduli of the pre-preg layer have been computed via a classical first-order linear homogenization, restricted to only in-plane constitutive components. To this end, only three linear perturbation analyses (i.e. two uniaxial and a pure shear analysis) have been performed, as shown in Fig. 5.

Fig. 5. Linear perturbation analyses for the evaluation of the homogenized tensor.

After this step, a nonlinear homogenization is performed under the application of a tensile loading able to promote global Mode-I crack propagation conditions. To this end, the Diffuse Interface Model (DIM) described in Section 2.2 has been used, by considering both fiber/matrix and matric/matrix damageable interfaces, characterized by the mixed mode cohesive fracture properties listed in Table 2.