PSI - Issue 28

Buşra M. Baykan et al. / Procedia Structural Integrity 28 (2020) 2055 – 2064 Baykan et al./ Structural Integrity Procedia 00 (2019) 000–000

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(2005). The elastic modulus in loading direction

, x E normal to loading direction

, y E in-plane shear modulus

xy G

and the Poisson’s ratio xy  of the laminate then can be calculated as * 12 * * * * 11 22 66 11 , . 1 1 1 , , x y xy xy A E E G v hA hA hA A      (9) The equivalent engineering constants in Eq. (9) are substituted in Eq. (6) in order to calculate the bond constants f c and . m c In PD, material failure can be considered by breaking the bonds between material points when the stretch in Eq. (3) reaches a critical value 0 . s The critical stretch, 0 s can be related to the fracture toughness 0 G by calculating the PD energy to break all the bonds per unit area Ha et al. (2010). 2 0 0 9 . 4 s E G    (10) PD mesh of the composite specimens with open holes are shown in Fig. 2a. Zoomed view of the PD mesh and the material points are illustrated in Fig. 2b. In this study, the grid size in OHT1 and OHT2-1 specimens are 0.667 x   mm. In OHT2-2, the grid size is reduced to 0.5 x   mm or more accuracy, since path3 is the shortest path.

b

a

OHT1

OHT2-1

OHT2-2

Path1

Path2

Path3

Fig. 2. Peridynamic mesh a) general view with holes b) zoomed view.

3.2. Finite Element Method FEA solution of the problem defined in Section 2 is conducted in ANSYS software. The FEA model of the specimens are generated with shell181 elements as shown in Fig. 3. The element size around the holes for OHT1 is 18 0.175   mm, OHT2-1 and OHT2-2 are 20 0.157   mm. To design a fine mesh region as shown in Fig. 3. specimens are divided on the symmetry planes, squares with the holes in the center are defined and rings are defined to get annular mesh around the holes as in Fig. 3. The equivalent material properties of the laminate in Özaslan et al. (2019) are calculated using Eq. (9).

OHT1

OHT2-1

OHT2-2

Fig. 3. FEA mesh around the holes of the specimens