Analysis of Impact Behavior of Thick Rotorcraft Composite Components: Approach and Implementation

The Sikorsky Aircraft Corporation (SAC) and the U.S. Army Aviation Development Directorate-Aviation Applied Technology Directorate (ADD-AATD) are jointly sponsoring the Capability-Based Operations and Sustainment Technology-Aviation (COST-A) program. The objective of COST-A is to demonstrate an integrated set of high-value diagnostics, prognostics, and system health management technologies that reduce the maintenance burden, without sacrificing safety, of six different rotorcraft systems, including the rotor impact detection and damage assessment. Impact damage behavior of large rotorcraft composite structures (RCS) is a complex problem and a challenging application for development of efficient and reliable predictive models. Thus, the objective of this work is a) development of a general approach of impact damage assessment, specifically for thick RCS; and b) demonstration of the approach on representative test articles. The approach is primarily based on multi-scale definition of RCS and test/model integration to understand and validate the most relevant damage mechanisms. Cohesive-element based FEA is applied for computational implementation of the approach. The approach was demonstrated on a main rotor blade (MRB) composite spar subjected to impact events. Representative examples that were investigated indicate the robust nature of the developed capabilities to capture multiple interlaminar damage patterns. Computational convergence is demonstrated for a range of load scenarios and damage mechanisms. Developed predictive capabilities can be used for systematic parametric studies to either define the worst case scenario for impact damage assessment or potential optimization of the internal structure in design to reduce susceptibility. It also may potentially help to reduce cost of full-scale testing and accelerate the entire certification process of RCS.