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An evaluation of mixed-mode delamination failure criteriaMany different failure criteria have been suggested for mixed mode delamination toughness, but few sets of mixed mode data exist that are consistent over the full mode I opening to mode II shear load range. The mixed mode bending (MMB) test was used to measure the delamination toughness of a brittle epoxy composite, a state of the art toughened epoxy composite, and a tough thermoplastic composite over the full mixed mode range. To gain insight into the different failure responses of the different materials, the delamination fracture surfaces were also examined. An evaluation of several failure criteria which have been reported in the literature was performed, and the range of responses modeled by each criterion was analyzed. A new bilinear failure criterion was analyzed. A new bilinear failure criterion was developed based on a change in the failure mechanism observed from the delamination surfaces. The different criteria were compared to the failure criterion. The failure response of the tough thermoplastic composite could be modeled well with the bilinear criterion but could also be modeled with the more simple linear failure criterion. Since the materials differed in their mixed mode failure response, mixed mode delamination testing will be needed to characterize a composite material. A critical evaluation is provided of the mixed mode failure criteria and should provide general guidance for selecting an appropriate criterion for other materials.
Document ID
19920009705
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Reeder, J. R.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 6, 2013
Publication Date
February 1, 1992
Subject Category
Composite Materials
Report/Patent Number
NASA-TM-104210
NAS 1.15:104210
Report Number: NASA-TM-104210
Report Number: NAS 1.15:104210
Accession Number
92N18947
Funding Number(s)
PROJECT: RTOP 505-63-50-04
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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