Structural Integrity of Composite and Adhesively Bonded Aircraft Structures from the Perspective of Multiaxial Cyclic Loading
Abstract
Composite and bonded structures are now widely used in a number of US Navy aircraft, viz: Triton, F/A-18 (Classic Hornet), Super Hornet, F-35, Sikorsky CH-53K King Stallion, etc. The current approaches used to certify composite and bonded structures are documented in the Mil-Std-1530, the United States Joint Services Structural Guidelines JSSG2006 and the Composites Materials Handbook CMH-17-3G. However, these approaches are based on a no damage growth design philosophy which is now known to be questionable. Consequently, existing science base and the associated test facilities do not enable the assessment of particular damage mechanisms such as disbonding/delamination or impact damage effects under representative multiaxial flight loads to be assessed. Similarly, the existing computer code (A4EI) used by the US Navy to assess bonded joints, such as that in the F/A-18 and the Super Hornet wings, and composite repairs to composite airframes does not allow for the combined effect of both axial and shear loads or their effect on the durability of the joint to be assessed. This project will provide the science base needed to overcome these shortcoming. As a result, this unique project will involve close collaboration with Dr. John Michopoulos’group, US Naval Research Lab., and Mr. Nam Phan, Naval Air Systems Command, Patuxent River, to: Develop a new, scientifically valid and unique rational basis for determining a proper lower bound for the fatigue threshold associated with delamination damage; Develop new test and analytical tools and extend solutions to bonded joints so as to allow for operational flight loads, i.e. combined axial and shear loads; Establish a statistically valid methodology for accounting for the large scatter seen in tests performed so as to determine the da/dN versus energy release rate curve for delamination growth in composite airframes; Establish the science base needed to determine conservative delamination growth rate curves. Establish if the delamination behaviour associated with small naturally occurring delaminations/disbonds differs from that seen in tests on specimens with large initial disbonds/delamination; Establish and validate a growth criteria for bonded and composite structures based on dissipated energy as well as on energy release rate concepts. Establish the science base needed to translate test data obtained using the NRL multi-axial test facility so as to apply representative flight load spectra with both axial and shear loads. The project is strongly supported by the Naval Air Systems Command who, in support of the project will provide test specimens representative of US Navy aircraft. It is also strongly supported by the RAAF Maritime Systems Project Office, RAAF Base Adelaide, who will make specimens representative of composite repairs to Triton Aircraft. (In the latter case the project will cover materials and manufacturing costs).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 23, 2019
- Source ID
- N629091912011
Entities
People
- Rhys Jones
Organizations
- Monash University
- Office of Naval Research
- United States Navy