Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781719392136
Total Pages : 30 pages
Book Rating : 4.3/5 (921 download)
Book Synopsis Evaluation of Delamination Onset and Growth Characterization Methods Under Mode I Fatigue Loading by : National Aeronautics and Space Administration (NASA)
Download or read book Evaluation of Delamination Onset and Growth Characterization Methods Under Mode I Fatigue Loading written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-05-22 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Double-cantilevered beam specimens of IM7/8552 graphite/epoxy from two different manufacturers were tested in static and fatigue to compare the material characterization data and to evaluate a proposed ASTM standard for generating Paris Law equations for delamination growth. Static results were used to generate compliance calibration constants for reducing the fatigue data, and a delamination resistance curve, GIR, for each material. Specimens were tested in fatigue at different initial cyclic GImax levels to determine a delamination onset curve and the delamination growth rate. The delamination onset curve equations were similar for the two sources. Delamination growth rate was calculated by plotting da/dN versus GImax on a log-log scale and fitting a Paris Law. Two different data reduction methods were used to calculate da/dN. To determine the effects of fiber-bridging, growth results were normalized by the delamination resistance curves. Paris Law exponents decreased by 31% to 37% after normalizing the data. Visual data records from the fatigue tests were used to calculate individual compliance constants from the fatigue data. The resulting da/dN versus GImax plots showed improved repeatability for each source, compared to using averaged static data. The Paris Law expressions for the two sources showed the closest agreement using the individually fit compliance data. Murri, Gretchen B. Langley Research Center DELAMINATING; CRACK BRIDGING; CANTILEVER BEAMS; FRACTURE STRENGTH; GRAPHITE-EPOXY COMPOSITES; FATIGUE (MATERIALS); CALIBRATING; FATIGUE TESTS; FITTING; DATA REDUCTION