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