Residual life predictions of composite aircraft structures via nondestructive testing, Part 2: Degradation modeling and residual life prediction

In the second part of this two part paper, we present a residual life predi ction model for the Harrier AV-8B horizontal stabilizer (see part 1 in the September 2000 Materials Evaluation, Vol. 58, No. 9, p 1065). The margins o f safety of composite structural components throughout the horizontal stabi lizer are used to define its structural integrity state. Specifically, we c onclude that when any of the strength, stiffness, or stability margins of s afety has been sufficiently reduced via any combination of damage mechanism s, the horizontal stabilizer may be said to have operationally failed and t hus must be replaced or repaired. Via the horizontal stabilizer's design margins of safety and empirical mode ls for the degradation of composite laminates, we devise margin of safety d eterioration surfaces and operational failure criteria that depict the func tional dependence of residual life on the local losses of strength and stif fness throughout the structure. Our results establish an analytic framework that can be applied not only to the Harrier AV-8B horizontal stabilizer, b ut also to a broad class of composite aircraft structures.