Reliability Analysis of Composite Rotorcraft Components

An analytical methodology is formulated to evaluate the reliability of tension‐loaded composite structures in the certification and design stages of product development. Use of coupon fatigue test data supported by energy release rate analysis in the design stage and of full‐scale fatigue test data in the certification stage is recommended for development of the damage growth tree, which is the basis for reliability determination. Since the presence of a delamination can be detected by visual inspection, the proposed methodology considers both noninspected and inspected cases. A fiberglass/epoxy main rotor yoke is used in an example problem to demonstrate the reliability analysis. The method used to determine the energy release rate, G, for delaminations of a yoke loaded with centrifugal force and beamwise and chordwise bending moments is given. The energy release rate analysis of the yoke is used to present full‐scale fatigue test data in terms of Gmax vs. N, which is then used to generate an S‐N curve for subsequent delaminations of the yoke.