Accession Number : ADA305265

Title :   Crack Propagation in Aluminum Sheets Reinforced with Boron-Epoxy.

Descriptive Note : Technical memo.,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER

Personal Author(s) : Roderick, G. L.

PDF Url : ADA305265

Report Date : MAR 1979

Pagination or Media Count : 248

Abstract : The literature has shown that crack propagation in cracked metal sheets can be significantly reduced by bonding an uncracked reinforcement to the metal sheet. However, cyclic debonding typically occurs over a localized area near the crack. Herein, an analysis was developed to predict both the crack growth and debond growth in a reinforced system. The analysis was based on the use of complex variable Green's functions for cracked, isotropic sheets and uncracked, orthotropic sheets to calculate inplane and interlaminar stresses, stress intensities and strain-energy-release rates. An iterative solution was developed that used the stress intensities and strain-energy-release rates to predict crack and debond growths, respectively, on a cycle-by-cycle basis. The analysis was verified with experiments. The analysis was used in a parametric study of the effects of boron-epoxy composite reinforcement on crack propagation in aluminum sheets. The study showed that the size of the debond area has a significant effect on the crack propagation in the aluminum. For small debond areas the crack propagation rate is reduced significantly, but these small debonds have a strong tendency to enlarge. Debond growth is most likely to occur in reinforced systems that have a cracked metal sheet reinforced with a relatively thin composite sheet. The analysis predicts crack growth in reinforced systems. Hence, the analysis can be applied in developing methods to repair damaged metal structures and to increase the lives and payloads of metal structures by selective reinforcement. (MM)

Descriptors :   *AIRCRAFT, *CRACK PROPAGATION, *ALUMINUM, *EPOXY COMPOSITES, *REINFORCING MATERIALS, *SHEET METAL, PARAMETRIC ANALYSIS, STRESS ANALYSIS, COMPOSITE MATERIALS, LAMINATES, FINITE ELEMENT ANALYSIS, SHEAR MODULUS, DISPLACEMENT, STRAIN(MECHANICS), ISOTROPISM, BONDING, FATIGUE(MECHANICS), GREENS FUNCTIONS, BORON, ITERATIONS, ADHESIVES.

Subject Categories : Aircraft
      Laminates and Composite Materials
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE