PSI - Issue 5

Khodjet-Kesba Mohamed et al. / Procedia Structural Integrity 5 (2017) 271–278 Khodjet-Kesba Mohamed et al / Structural Integrity Procedia 00 (2017) 000 – 000

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a and b are constants and N is the total number of plies. From Lundgren and Gudmundson (1999) the values of a=5.96 and b=1.43 are obtained. The presented model is applied to [0/90] 2s glass/epoxy reported by Talerja (1986), which the mechanical properties of fibre and matrix of the lamina are listed in Table 2. The Single ply thickness = 0.203 mm, √ = 0.3 and Fibre volume fraction V f = 0.45 . Table 2. Fibre and matrix characteristics of glass/epoxy material Talerja (1986). (Gpa) 12 (Gpa) 12 Fibre 84 33.6 0.27 Matrix 3.2 1.26 0.27

4.1. Moisture absorption effect on the longitudinal stress along the laminate

0,30

i=1 (T=22°C) i=2 (T=60°C) i=3 (T=120°C)

0,25

0,20

0,15

0,10

 90 xx /  c

0,05

0,00

-0,05

-0,10

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 -0,15

X/l

Fig. 5. Hygrothermal effect on the longitudinal stress σ xx along the length of [0/90 3 ] s laminates with a=1 and Vf=0.7

With a parabolic variation of the longitudinal displacement across the thickness of the layer at 90° and 0°, a reduction in the longitudinal stress in the layer 90 is being much lower than σ c in the case of increasing in temperature (Fig. 5) and for high c rack densities on a large part of the crack spacing (0 ≤x / l ≤0.7). Then the longitudinal stress decreases and tends to be in compression at the crack plane. The hygrothermal effect is more observed with increasing of the cracking aspect ratio.

4.2. Moisture absorption effect on the interlaminar shear stress along the laminate

Figures 6 shows the influence of the moisture absorption effect on the variation of the interlaminar shear stress at the interface between the 0° and 90° layers as a function of longitudinal coordinate for the [0/903]s laminate. The results show a remarkable influence of hygrothermal conditions for interlaminar shear stress on a large part of crack spacing (0.2 ≤ x/l ≤ 1). A maximum rate of reduction, approximately 9% is observed between cracked cross-ply under standard environment (T=22 ° C) and the other under high temperature (T=120°C). The hygrothermal effect in the case of the absorption makes very interesting the study of the interlaminar shear stress on the cross-ply composite laminates with transverse cracking and delamination between the 0° and 90° layers.