PSI - Issue 28

Mohamed Khodjet Kesba et al. / Procedia Structural Integrity 28 (2020) 864–872 KHODJET KESBA Mohamed/ Structural Integrity Procedia 00 (2019) 00 – 00

869

6

1,00

Parabolic analysis Progressif shear Variational model Experimental [9]

0,95

Ex/Ex 0

0,90

0,85

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 0,80

Crack density (1/mm)

Fig. 2. Longitudinal Young’s modulus degradation due to transverse cracks in a [0/45] s glass/epoxy laminate with t 45 =0.61mm.

1,00

Parabolic analysis Progressif shear Variational model Experimental [9]

0,95

Ex/Ex 0

0,90

0,85

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 0,80

Crack density (1/mm)

Fig. 3. Longitudinal Young’s modulus degradation due to transverse cracks in a [0/45] s glass/epoxy laminate with t 45 =0.64mm.

3.2 Influence of hygrothermal conditions on the reduced Young’s modulus The study, here has been focused on the stiffness reduction due to transverse ply cracking in [0/β 3 ] s laminate when this latter is initially exposed to the hygothermal aging submitted to transient and non-uniform moisture concentration distribution in desorption case. For that the model which will enable us to introduce ageing and to see its development on the fiber and matrix scales is the Tsai model (1988). Tsai (1988) proposes the adimensional temperature T*, which is the essential parameter for evaluation of the hygrothermal effect in stress distribution: (28) Where T g is the glass transition temperature, T opr is the operating temperature and T rm is the room temperature.We further assume that moisture suppresses the glass transition temperature by simple temperature shift. (29) Let us consider a laminated plate of thickness h made of polymer matrix composite, submitted on it two sides to the same dry environment. The plate is considered to be infinite in both x and y directions and the moisture vary only in the z direction. The initial moisture concentration C init is uniform at t=0. Both sides of the plate are suddenly exposed to a zero moist environment (Fig. 4). The moisture concentration inside the plate is described by Fick equation (Shen and Springer (1981)) with diffusivity D z . g rm opr g T T T T T    * 0 g T T T gc g g   0