Here we derive the laminate coefficients hygral expansion, 
, for symmetric laminates. Let us define the coefficient of hygral expansion for laminate as laminate mid-plane strains to the per percentage change in moisture absorption, 
. Thus,
 | (5.121) |
For symmetric laminates with hygral loads alone, we can write
 | (5.122) |
Combining Equation (5.121) and Equation (5.122), we get
 | (5.123) |
For a uniform moisture absorption the equivalent hygral force is given as
 | (5.124) |
Thus, the laminate coefficient of hygral expansion becomes
 | (5.125) |
It is known that the 
and 
are constant in each lamina in thickness direction. Thus, the integration over thickness can be simplified as summation over laminae thicknesses as
 | (5.126) |
Combining Equation (5.124) and Equation (5.125) we can get the effective hygral force as
 | (5.127) |
Figure 5.15 shows the variation of 
for 
laminate along with 
of a layer of 
for T300/5208 material from Pipes et al [5]. Similarly, Figure 5.16 and Figure 5.16 show the variation of 
and 
.
|
| Figure 5.15: Variation of for lamina and of for laminate |
|
| Figure 5.16: Variation of for lamina and of for laminate |
|
| Figure 5.17: Variation of for lamina and of for laminate |
