distributions. For large failure probability, increasing the mean value of E2u is more
effective. Increasing the mean value of E2u by 10 percent or truncating 82u at 2cr can
reduce the laminate thickness to 0.10 inch for a safety level of le-4. Combining all three
measures together, the laminate thickness can be reduced to 0.08 inch with a safety level
of le-7.
Table 5-17 shows the changes of maximum E2 calculated by the laminate analyses.
Ten percent changes of the mean values of E2, Tzero, and a2 (Same CV) will lead to about
5% change in the maximum E2, which indicate that further study needs to focus on the
three quantities. Table 5-18 shows the probabilities of failure are reduced by a factor of
five by 10 percent change of the mean values of E2, Tzero, and a2 (Same CVs). This
reduction of probability shows the potential of further improvements via improvements in
all three material properties.
1.0E+00
-*-Nominal
1.0E-01 -Qual~ity control to -2 Sigma
-%-10% mecrease in allowable
1.0E-02 % rex~~ duction in variability~l
S1.0E-03
1.0E-07
1.0E-08
0.06 0.08 0.1 0.12 0.14 0.16
Thickness (inch)
Figure 5-1. Tradeoff plot of probability of failure, cost, and weight (laminate thickness)
for [+25]s