CHAPTER 5
RELIABILITY-BASED DESIGN OF COMPOSITE LAMINATES FOR CRYOGENIC
ENVIRONMENTS
This chapter presents reliability-based designs of composite laminates for hydrogen
tanks in cryogenic environments, comparison between deterministic and reliability-based
design, identification of uncertainty parameters that have the largest influence on the
optimum design, and quantification of the weight penalty associated with level of
uncertainty in those parameters. The results indicate that the most effective measure for
reducing thickness is quality control (refer also to Qu et al., 2001). The reliability-based
optimization is carried out using response surface approximations combined with Monte
Carlo simulation described in chapter three.
Reliability-Based Design Optimization
Problem Formulation
The reliability-based optimization is formulated as
minimize h= 4(tz +t2)
such that
P < P"
0.005 < t, 51
0.005 < t2
where h is the laminate thickness, tl is the stack thickness of lamina with ply-angle 6, and
has a lower limit of 0.005 inch on it, t2 is the stack thickness of lamina with ply-angle 82
and has a lower limit of 0.005 inch. The limits on tl and t2 alSo ensure that the laminate
has a minimum thickness of 0.04 inch to prevent hydrogen leakage. The reliability