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Description / Abstract:
Composite cylinders have been used for over 50 years in
commercial, vehicle, defense and aerospace applications. New
materials, processes, design approaches and applications have been
incorporated during that time. The industry has maintained a high
level of safety. The industry has adapted to these changes and has
developed new and revised standards to address these changes and to
reflect a better understanding of service conditions.
Recommendations are made that the industry:
• Continue to monitor field use and incorporate changes to
requirements, standards and codes that reflect knowledge gained for
composite pressure vessels,
• Use a failure modes and effects analysis (FMEA) approach to
standards, using the knowledge gained from field experience,
• Develop standards for composite pressure vessels that are more
performance based to improve both safety and performance,
• Address requirements using performance testing, not by using
excessive safety factors,
• Use stress ratios for the various reinforcing fibers that
accurately reflect their stress rupture and fatigue characteristics
to achieve high reliability, Harmonize testing requirements where
practical, Use qualification tests that are appropriate for the
application and for the materials and design features of the
pressure vessels being used, and
• Consider using fleet leader programs for new materials,
designs or applications if there is likely to be a significant
safety issue
To support these recommendations, history of use of composite
cylinder in aerospace/defense, commercial and vehicle applications
is reviewed. This includes review of applications, materials of
construction; standards used and field service issues.
The use of performance-based requirements is discussed, as is
the background of safety factors used for various reinforcing
fibers. Recommendations are made for validation testing of
materials and pressure vessels, with consideration for failure
modes and effects analysis (FMEA) involving the field use of the
vessels.
Cyclic fatigue and stress rupture are discussed, with examples
of laboratory testing and correlation from field experience.