further. Table 5-12 shows that this conclusion applies also to the elastic moduli,
coefficients of thermal expansion, and stress-free temperature. By comparing with Table
5-10, we see that truncating any of the other parameters at -2 o does not change the
failure probability as significantly as truncating 82u at -4 o. Note that some probabilities
from truncated distributions are slightly larger than those from untruncated distributions,
which is due to the sampling errors.
Table 5-11i. Effects of quality control of st", sil, E21, and Y12 On probability of failure of
0.12 inch-thick (f6)s laminates
Probability of failure from MCS 10,000,000 samples
Un-truncated Truncated Truncated Truncated Truncated
Normal e1U at -20 s/1 at -20 eat at -20 77, at -20
24.00 60.5e-6 58.6e-6 61.5e-6 54.4e-6 55.4e-6
25.00 56.5e-6 53.0e-6 52.3e-6 54.0e-6 53.2e-6
26.00 60.7e-6 63.4e-6 62.0e-6 60.1e-6 61.0e-6
Table 5-12. Effects of quality control of El, E2, G12, Cl12, Tzero, al, and a2 On probability
of failure of 0. 12 inch-thick (f6)s laminates
Probability of failure from MCS 10,000,000 samples by truncating
B at -20
E1 Ez Gol go1 Tzero ao at
24.00 62.2e-6 52. 1e-6 57.8e-6 51.8e-6 54.6e-6 52.7e-6 58.2e-6
25.00 52.5e-6 48. 1e-6 55.1e-6 49.7e-6 55.1e-6 56.8e-6 54.4e-6
26.00 54.5e-6 59. 1e-6 60.4e-6 59.4e-6 59.8e-6 63.0e-6 60.4e-6
Effects of Quality Control on Optimal Laminate Thickness
Quality control (QC) can be used to reduce the laminate thickness instead of the
probability of failure. Table 5-13 shows that QC of EZu at -30 will allow 0.1 inch-thick
laminates with failure probability below the required 0.0001.