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notch strength of compositesThe notch strength of composites is discussed. The point stress and average stress criteria relate the notched strength of a laminate to the average strength of a relatively long tensile coupon. Tests of notched specimens in which microstrain gages have been placed at or near the edges of the holes have measured strains much larger that those measured in an unnotched tensile coupon. Orthotropic stress concentration analyses of failed notched laminates have also indicated that failure occurred at strains much larger than those experienced on tensile coupons with normal gage lengths. This suggests that the high strains at the edge of a hole can be related to the very short length of fiber subjected to these strains. Lockheed has attempted to correlate a series of tests of several laminates with holes ranging from 0.19 to 0.50 in. Although the average stress criterion correlated well with test results for hole sizes equal to or greater than 0.50 in., it over-estimated the laminate strength in the range of hole sizes from 0.19 to 0.38 in. It thus appears that a theory is needed that is based on the mechanics of failure and is more generally applicable to the range of hole sizes and the varieties of laminates found in aircraft construction.
Document ID
Document Type
Conference Paper
Whitney, J. M.
(Air Force Wright Aeronautical Labs. Wright-Patterson AFB, OH, United States)
Date Acquired
August 11, 2013
Publication Date
August 1, 1983
Publication Information
Publication: NASA. Langley Research Center Failure Anal. and Mech. of Failure of Fibrous Composite Struct.
Subject Category
Distribution Limits
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19830025686Analytic PrimaryFailure Analysis and Mechanisms of Failure of Fibrous Composite Structures