Accession Number : ADA307681

Title :   Analytical and Experimental Investigation of Aircraft Metal Structures Reinforced with Filamentary Composites. Phase 2. Structural Fatigue, Thermal Cycling, Creep, and Residual Strength.

Descriptive Note : Contract rept.,

Corporate Author : BOEING CO SEATTLE WA

Personal Author(s) : Blichfeldt, B. ; McCarty, J. E.

PDF Url : ADA307681

Report Date : JUN 1972

Pagination or Media Count : 104

Abstract : Specimens representative of metal aircraft structural components reinforced with boron filamentary composites were manufactured and tested under cyclic loading, cyclic temperature, or continuously applied loading to evaluate some of the factors that affect structural integrity under cyclic conditions. Bonded, stepped joints were used throughout to provide composite-to-metal transition regions at load introduction points. Honeycomb panels with titanium or aluminum faces reinforced with unidirectional boron composite were fatigue tested at constant amplitude under completely reversed loading. Results indicated that the matrix material was the most fatigue-sensitive part of the design, with debonding initiating in the stepped joints. However, comparisons with equal weight all-metal specimens show a 10 to 50 times improved fatigue life. Fatigue crack propagation and residual strength were studied for several different stiffened panel concepts, and were found to vary considerably depending on the configuration. Weight savings up to 30 percent may be realized with the better concepts when compared to all-metal structure. Composite-reinforced metal specimens were also subjected to creep and thermal cycling tests. The creep tests at 50 percent of tensile ultimate load were inconclusive due to large scatter in the limited tests. Thermal cycling of stepped joint tensile specimens resulted in a ten percent decrease in residual strength after 4000 cycles.

Descriptors :   *COMPOSITE MATERIALS, *FATIGUE(MECHANICS), *REINFORCEMENT(STRUCTURES), TEST AND EVALUATION, TEMPERATURE, SCATTERING, FATIGUE LIFE, STRUCTURAL PROPERTIES, LOADS(FORCES), STIFFNESS, TENSILE PROPERTIES, METAL MATRIX COMPOSITES, MATRIX MATERIALS, STRENGTH(MECHANICS), CYCLES, REGIONS, CRACK PROPAGATION, RESIDUALS, REVERSIBLE, HEATING, AIRFRAMES, CREEP, FILAMENTS, TITANIUM, AIRCRAFT EQUIPMENT, TRANSITIONS, CONTINUITY, BORON, AMPLITUDE, WEIGHT REDUCTION, THERMAL CYCLING TESTS, AIRCRAFT PANELS, UNIDIRECTIONAL, HONEYCOMB STRUCTURES, STRUCTURAL INTEGRITY.

Subject Categories : Aircraft
      Laminates and Composite Materials
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE