AIAA-30895-180 - JOURNAL OF AIRCRAFT Vol 44 No 6...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Bending of Bonded Composite Repairs for Aluminum Aircraft Structures: A Design Study Randal J. Clark and Douglas P. Romilly University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada DOI: 10.2514/1.30895 This paper describes an experimental and fi nite element study of a bonded composite repair applied to a metallic aircraft structure. The experimental study involves the fatigue testing and fractographic examination of 2024-T3 aluminum plates repaired with boron/epoxy composite patches. The two plates are tested simultaneously in a sandwich panel con fi guration with and without an aluminum honeycomb spacer to provide bending restraint. The specimen was heavily instrumented, with strains being measured on the surface of the patch at many locations, thus allowing the validation of a three-dimensional fi nite element model and an assessment of the effects of geometrically nonlinear bending, buckling, and crack closure on the mechanical response and strength of the repair. The experimental and fi nite element results illustrate the important in uence of bending and composite failure modes on the life and strength of the repair. The authors use the experimental results and the validated fi nite element analysis to evaluate the effectiveness of the methods and data currently available in the open literature for damage-tolerance substantiation, and then, by applying probabilistic methods and the principle of compounded conservatism to the fi ndings, propose a new process for classifying bonded repairs and assigning requirements for testing and inspections. Nomenclature a = crack length E = Young s modulus G = shear modulus or strain energy release rate K = stress-intensity factor p = pressure r = radius of the patch t = thickness = coef fi cient of thermal expansion = Poisson s ratio = normal stress = shear stress Subscripts a = adhesive property b = bending m = membrane p = plate property I = opening mode II = sliding mode I. Introduction A BONDED composite patch is a fi ber-reinforced epoxy doubler used to reinforce weak structure or repair cracked aircraft structure. The patch acts both to reduce stresses in the underlying structure and to restrict the opening of cracks that may lie beneath the structure. These effects and the smooth load transfer inherent to bonding offer the potential for a signi fi cant increase in fatigue life when compared with mechanically fastened repairs (shown in Fig. 1). The technology also offers improvements in cost,weight, and inspectability. The main barrier to the widespread use of this technology is the lack of a comprehensive process for damage- tolerance analysis, particularly regarding the mechanical assessment of the structure in the presence of signi fi cant bending loads, which can lead to early failure. The other signi fi cant impediment is the assurance of bond durability for repairs applied in a maintenance and repair facility.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern