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Analysis of delamination in unidirectional and crossplied fiber composites containing surface cracksA two-dimensional hybrid stress finite element analysis is described which was used to study the local stress field around delamination cracks in composite materials. The analysis employs a crack tip singularity element which is embedded in a matrix interlayer between plies of the laminate. Results are given for a unidirectional graphite/epoxy laminate containing a delamination emanating from a surface crack through the outside ply. The results illustrate several aspects of delamination cracks: (1) the localization of the singular stress domain within the interlayer; (2) the local concentration of stress in the ply adjacent to the crack; (3) the nature of the transverse normal and interlaminar shear stress distributions; and (4) the relative magnitudes of K sub 1 and K sub 2 associated with the delamination. A simple example of the use of the analysis in predicting delamination crack growth is demonstrated for a glass/epoxy laminate. The comparisons with experimental data show good agreement.
Document ID
19780003254
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Wang, S. S. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Mandell, J. F. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Date Acquired
September 3, 2013
Publication Date
May 1, 1977
Subject Category
Composite Materials
Report/Patent Number
NASA-CR-135248
Accession Number
78N11197
Funding Number(s)
CONTRACT_GRANT: NSG-3044
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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