NATIONAL INSTITUTE OF AEROSPACE

FAA Awards Cooperative Agreement on the Study of Damage Modes in Lightweight Sandwich Structures Using Analysis and Testing

FAA Awards Cooperative Agreement on the Study of Damage Modes in Lightweight Sandwich Structures Using Analysis and Testing

 

The Federal Aviation Administration (FAA) most recently awarded a cooperative agreement onthe Study of Damage Modes in Lightweight Sandwich Structures Using Analysis and Testing to support research at the FAA’s William J. Hughes Technical Center in Atlantic City, New Jersey. Dr. Ronald Krueger, Associate Research Fellow at the National Institute of Aerospace, will serve as principal investigator (PI) for the technical effort, with support from Dr. Leif Carlsson, Co-PI, Florida Atlantic University, and Dr. George Kardomateas, Co-PI, Georgia Institute of Technology. Overall project management will be handled by NIA’s Director of FAA Programs, Mr. Peter McHugh.

The work done under this cooperative agreement will provide a methodology to assess the impact of weather and environment on sandwich composite structures ability to survive under conditions encountered during the service life of current and future civil aircraft.  Delivery of this methodology will assure that designs incorporating sandwich composite structures in the future provide the equivalent or better level of structural safety in advanced materials as that found in historic aircraft designs.

Typical damage modes observed in light honeycomb sandwich structures are face sheet/core disbonding and core fracture, both of which can pose a threat to the structural integrity of a component. These damage modes are of particular interest to certification and aircraft safety technology authorities since in-service occurrences such as rudder structural failure and other control surface malfunctions have been attributed to disbonding. Extensive studies have shown that face sheet/core disbonding and core fracture can lead to damage propagation caused by internal pressure changes in the core due to ground-air-ground (GAG) cycles.  Future composite structure applications, including for instance, composite sandwich construction of the fuselage of business jets that see higher altitudes than transport aircraft, are also driving a need to understand the phenomena of disbond growth under generalized load conditions including maneuver and meteorological (e.g., gust) conditions as well as related environmental conditions such as heat and moisture. The ability to identify, predict and prevent disbonding has important safety implication as loss of structural integrity or components in flight can be catastrophic.

The specific objectives are divided into three parts.  These parts are aligned with the FAA plan for sandwich structures characterization as developed by the task team from the Composite Materials Handbook CMH-17 Disbond/Delamination Task Group. The first part, performed by NIA, will support the development of an analysis and test capability, in support of advanced aircraft materials safety and certification activity at the FAA’s William J. Hughes Technical Center in Atlantic City. The second and third parts will support the broader FAA aircraft structures and certification safety effort by characterizing damage modes in sandwich composite structures and reactions of such structures to environmental conditions. In particular, the second part, performed by Florida Atlantic University (FAU), will focus on the development of characterization test methods and associated data reduction techniques. The third part, performed by Georgia Institute of Technology (GT), will focus on the development of closed form algebraic expressions for the energy release rate and the mode mixity for a disbonded sandwich construction.

NIA POC: David Throckmorton, Vice President of Research, david.throckmorton@nianet.org, 757.325.6724

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