Table 4-5. Optimal laminates for temperature dependent material properties with Ezu Of
 0.0110 (optimized for 21 temperatures)

 6, 6,t; tha (inch) Probability of failure
 (degree) (degree) (inch) (inch)
 0.00 28.16 0.005 0.020 0.100 (0.103) 0.019338 (0.014541)
 27.04 27.04 0.010 0.015 0.100 (0.095) 0.000479 (0.001683)
 25.16 27.31 0.005 0.020 0.100 (0.094) 0.000592 (0.001879)
a Numbers in parentheses indicate unrounded thickness
b The probabilities were calculated by the methodology described in the chapter 5


-


 SEpsilon1 Epsilon2 +-Gammal 2




- 4 M~2


0.012
0.010
0.008
0.006
0.004
0.002
0.000
-0.002!
-0.004
-0.006


 Temperature (oF)



Figure 4-5. Strains in optimal laminate for temperature dependent material properties
 with EZu Of 0.01 10 (second design in Table 4-3)

 These optimal laminates have similar thickness but different ply angles. The failure

probabilities of the continuous designs are shown in parentheses. The high failure

probabilities of the first design (continuous and discrete) clearly show a smaller safety

margin than the other two. The second and third designs show that a slight rounding can

change the failure probability significantly. Designs with two similar ply angles have

much lower failure probabilities than designs with two substantially different ply angles.

The failure probabilities of these laminates are too high (compared with 10-4 to 10-6), and

this provides incentives to conduct reliability-based design.