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Effects of T-tabs and large deflections in DCB specimen testsA simple strength of materials analysis was developed for a double-cantilever beam (DCB) specimen to account for geometric nonlinearity effects due to large deflections and T-tabs. A new DCB data analysis procedure was developed to include the effects of these nonlinearities. The results of the analysis were evaluated by DCB tests performed for materials having a wide range of toughnesses. The materials used in the present study were T300/5208, IM7/8551-7, and AS4/PEEK. Based on the present analysis, for a typical deflection/crack length ratio of 0.3 (for AS4/PEEK), T-tabs and large deflections cause a 15 percent and 3 percent error, respectively, in the computer Mode 1 strain energy release rate. Design guidelines for DCB specimen thickness and T-tab height were also developed in order to keep errors due to these nonlinearities within 2 percent. Based on the test results, for both hinged and tabbed specimens, the effects of large deflection on the Mode 1 fracture toughness (G sub Ic) were almost negligible (less than 1 percent) in the case of T300/5208 and IM7/8551-7; however, AS4/PEEK showed a 2 to 3 percent effect. The effects of T-tabs G sub Ic were more significant for all the materials with T300/5208 showing a 5 percent error, IM7/8551-7 a 15 percent error, and, AS4/PEEK a 20 percent error.
Document ID
19900007552
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Naik, R. A.
(NASA Langley Research Center Hampton, VA., United States)
Shivakumar, K. N.
(Analytical Services and Materials, Inc., Hampton VA., United States)
Crews, J. H., Jr.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 6, 2013
Publication Date
November 1, 1989
Subject Category
Composite Materials
Report/Patent Number
NASA-TM-101677
NAS 1.15:101677
Accession Number
90N16868
Funding Number(s)
PROJECT: RTOP 505-63-01-05
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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