Probabilistic Structural Integrity Framework for Composite Damage Tolerance

Airframes in the future will include a significant amount of composite material components that need to be designed for both optimal structural efficiency and damage tolerance. Current composite design methodology relies on the establishment of worst-case scenarios for each of the factors that influence the structural capacity and life of airframe components. The layered application of these factors can result in excessive levels of conservatism and maintenance requirements that reduce aircraft availability. The combat aircraft of the future can be designed and maintained based on specific knowledge derived from data driven methodologies to define risk, threat impact, and measured structural response in order to maximize aircraft availability, while ensuring safety and reliability. This work describes an Advanced Structural Integrity Framework (ASIF) that probabilistically models composite residual strength. Full-scale damage tolerance tests of a UH-60M stabilator provided input data for various threat types and severities. Threat probabilities were derived from prior studies and recent fleet repair data. The model estimated the risk of failure in various structural zones to identify areas for reducing conservatism. Trend studies confirmed that the model appropriately responded to changes in composite material properties and threat exposures, thus showing its potential as a powerful structural risk assessment tool for design and fleet management.