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Measurement of multiaxial ply strength by an off-axis flexure testAn off-axis flexure (OAF) test was performed to measure ply strength under multiaxial stress states. This test involves unidirectional off-axis specimens loaded in bending, using an apparatus that allows these anisotropic specimens to twist as well as flex without the complications of a resisting torque. A 3D finite element stress analysis verified that simple beam theory could be used to compute the specimen bending stresses at failure. Unidirectional graphite/epoxy specimens with fiber angles ranging from 90 deg to 15 deg have combined normal and shear stresses on their failure planes that are typical of 45 deg plies in structural laminates. Tests for a range of stress states with AS4/3501-6 specimens showed that both normal and shear stresses on the failure plane influenced cracking resistance. This OAF test may prove to be useful for generating data needed to predict ply cracking in composite structures and may also provide an approach for studying fiber-matrix interface failures under stress states typical of structures.
Document ID
19920015637
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Crews, John H., Jr. (NASA Langley Research Center Hampton, VA, United States)
Naik, Rajiv A. (Analytical Services and Materials, Inc., Hampton VA., United States)
Date Acquired
September 6, 2013
Publication Date
March 1, 1992
Subject Category
Structural Mechanics
Report/Patent Number
NASA-TM-107570
NAS 1.15:107570
Meeting Information
Meeting: ASTM Symposium on Composite Materials: Testing and Design
Location: Pittsburgh, PA
Country: United States
Start Date: May 4, 1992
End Date: May 5, 1992
Accession Number
92N24880
Funding Number(s)
PROJECT: RTOP 505-63-50
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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