Optimum Panel Design

 Using the DRS of the PSF in Table 8-9, reliability-based design optimization is

performed. The optimum design is shown in Table 8-10. Its reliability evaluated by MCS

using ARS, whose error statistics are shown in Table 8-5, with 106 Samples is shown in

Table 8-11. It is seen that the reliability-based design is slightly lighter and safer than the

deterministic design. The probability of failure of reliability-based design is slightly

higher than the target reliability, which is due to the errors in the ARS approximation.

The design can be refined by another design iteration that use a smaller design domain

centered around it.

Table 8-10. Optimum panel design
 b h tl t2 Weight (lb)

 10.70 1.9854 0.1004 0.1246 2581


Table 8-1 1. Probabilities of failure calculated by Monte Carlo simulation of 1x106
 samples
 Probability of failure of Probability of failure of System probability of
 load case 1 load case 2 failure
 0 123x10-6 123x10-6


 Composite Isogrid Panel Design Example

 Next we consider a composite isogrid panel. The panel and the zero degree

direction for the composite angle ply laminates in isogrid and skin are shown in Figure 2.

It is shown in chapter four that angle ply laminates with plies oriented close to each other

is a good design for cryogenic environments due to reduced residual strains. Two

additional design variables are the ply angles of angle ply laminates in the isogrid and

skins, Bi and 62, TOSpectively. Reliability-based optimization seeks the lightest structures