Table 5-13. Effects of quality control of EZu On probability of failure for 0. 1 inch-thick
(+6)s laminates
Probability of failure from MCS 1,000,000 samples
Un-truncated Truncate at Truncate at Truncate at
Normal -4a (3/100,000) -3 a(14/10,000) -2.5 a(6/1,000)
24.00 0.002224 0.002163 0.001054 0.000071
25.00 0.001030 0.000992 0.000229 0.000007
26.00 0.000615 0.000629 0.000092 0.000003
Table 5-14 shows that QC of EZu at -1.60, which corresponds to rejecting 55
specimens out of 1000, will reduce the thickness to 0.08 inch with a failure probability
below 0.0001. Therefore, the laminate thickness can be reduced to 0.08 inch if QC is able
to find and rej ect 55 specimens out of 1000.
Table 5-14. Effects of quality control of EZu On probability of failure for 0.08 inch-thick
(+6)s laminates
Probability of failure from MCS 1,000,000 samples
Un-truncated Truncate at Truncate at Truncate at
Normal -30(14/10,000) -20(23/1,000) -1.60 (55/1,000)
24.00 0.061204 0.060264 0.039804 0.015017
25.00 0.028289 0.027103 0.008820 0.001019
26.00 0.013595 0.012154 0.001243 0.000071
Effects of Other Improvements in Material Properties
Instead of quality control, it is possible to improve the design by using a better
material. Table 5-15 shows the effects of changing the mean value of E2u by f 10 percent
of the nominal value of 0.0154. Comparison with Table 5-10 shows that a 10%
improvement has big influence on failure probability but is not as powerful as quality
control at -30 level.