PSI - Issue 72

Mohamed Khodjet Kesba et al. / Procedia Structural Integrity 72 (2025) 164–171

167

4. Hygrothermal stress The change in temperature produces a thermal expansion (extension or contraction) of the material. The thermal expansion phenomena can be described by writing the deformations at a point M, and at time t in the form:

*

(10)

( , ) z t

.

e

T

i   





i thermal

The dilatation phenomena by absorption or desorption humidity, lead to similar effects to thermal effects, déformations that result can be put in the form:

*

(11)

( , ) z t

( , ).

e

C z t

i   

 hygroscpic i



The resultants of the hygrothermal forces are given by:

N N

xx Q Q Q e Q Q Q e t Q Q Q e       xy xs x yx yy ys y      

    

   

   

HT

x

( / ) 1 h dz 

(12)



.

HT

  

y

i

1

i



N

HT



xy

sx

sy

ss

s i

i

Hygrothermal moments are defined as follows:

M M

Q Q Q e    

    

    

HT

x

xx

xy

xs

x

   

y         

( / ) 1 h dz 



(13)

.

Q Q Q e zt



HT

y

yx

yy

ys

i i

1

i



M

Q Q Q e

HT



xy

sx

sy

ss

s i

i

Table 1 – Characteristics of graphite / epoxy (T300/5208) [4],[5],[12]. Efx Efy υfx Em νm Vf T°g(°C) 259 18.69 0.25, 3.4 0.35 0.7 160

Trm(°C) g(°C/c) a

b c

f

h

e

22

2000 0.5 0.2 0.9 0.04 0.04 0.2

αx(10 -6k-1) αy(10 -6k-1)

βx βy 0.0 0.6

T300/5208

0.02

22.5

Residual deformations in each sublayer i are given by:

xx         x yy           y xy s i i e e e   

xx         yy xy     

.

 

(14)

i residuelles

Residual stresses in the xy landmark for each sublayer i are given by: \