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A curved beam test specimen for determining the interlaminar tensile strength of a laminated compositeA curved beam type of test specimen is evaluated for use in determining the through-the-thickness strength of laminated composites. Two variations of a curved beam specimen configuration (semicircular and elliptical) were tested to failure using static and fatigue loads. The static failure load for the semicircular specimens was found to be highly sensitive to flaw content, with the specimens falling into two distinct groups. This result supports the use of proof testing for structural validation. Static design allowables are derived based on the Weibull distribution. Fatigue data indicates no measured increase in specimen compliance prior to final fracture. All static and fatigue failures at room temperature dry conditions occurred catastrophically. The elliptical specimens demonstrated unusually high failure strengths indicating the presence of phenomena requiring further study. Results are also included for specimens exposed to a wet environment showing a matrix strength degradation due to moisture content. Further testing is underway to evaluate a fatigue methodology for matrix dominated failures based on residual static strength (wearout).
Document ID
19910065507
Document Type
Reprint (Version printed in journal)
Authors
Hiel, Clement C. (NASA Ames Research Center Moffett Field, CA, United States)
Sumich, Mark (NASA Ames Research Center Moffett Field, CA, United States)
Chappell, David P. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 14, 2013
Publication Date
July 1, 1991
Publication Information
Publication: Journal of Composite Materials
Volume: 25
ISSN: 0021-9983
Subject Category
STRUCTURAL MECHANICS
Distribution Limits
Public
Copyright
Other