Investigation of Joints in Advanced Fibrous Composites for Aircraft Structures. Joint and Attachment Investigation. Volume 1. Technical Discussion and Summary
Final rept. 25 Apr 1967-28 Mar 1969
DOUGLAS AIRCRAFT CO LONG BEACH CA
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To find ways of efficiently joining composite materials, an investigation was undertaken to explore design philosophies, identify parameters affecting joint strength and life, establish design approaches for aircraft applications, and compile design data. Properties of boron and fiber glass laminates were determined in tension, compression, in-plane shear, interlaminar shear, and pin-bearing tests. In comparing six adhesives, a nylon-epoxy adhesive was found to have the best combination of shear strength and ductility. Ultimate strength and fatigue data were determined for a variety of bonded joint and bolted joint test specimens. The effects of design parameter variations on joint failure modes were determined, and parametric strength trends were analyzed. A combination bolted-bonded joint performed better than joints employing either bolting or bonding separately because of a fundamental change in failure mode caused by adhesivefastener interaction. On a weight-efficiency basis, bonded joints were found to be superior to bolted joints. Scarf and stepped lap bonded joints, although more difficult to fabricate than lap joints, showed promise of achieving any desired strength with only a small weight penalty. Fabrication techniques of the specimens are described.
- Laminates and Composite Materials
- Couplers, Fasteners and Joints