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Hygrothermal effects on mechanical behavior of graphite/epoxy laminates beyond initial failureAn investigation was conducted to determine the critical load levels and associated cracking beyond which a multidirectional laminate can be considered as structurally failed. Graphite/epoxy laminates were loaded to different strain levels up to ultimate failure. Transverse matrix cracking was monitored by acoustic and optical methods. Residual stiffness and strength that were parallel and perpendicular to the cracks were determined and related to the environmental/loading history. Results indicate that cracking density in the transverse layers has no major effect on laminate residual properties as long as the angle ply layers retain their structural integrity. Exposure to hot water revealed that cracking had only a small effect on absorption and reduced swelling when these specimens were compared with uncracked specimens. Cracked, moist specimens showed a moderate reduction in strength when compared with their uncracked counterparts. Within the range of environmental/loading conditions of the present study, it is concluded that the transverse cracking process is not crucial in its effect on the structural performance of multidirectional composite laminates.
Document ID
19840024368
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Ishai, O. (NASA Ames Research Center Moffett Field, CA, United States)
Garg, A. (NASA Ames Research Center Moffett Field, CA, United States)
Nelson, H. G. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 4, 2013
Publication Date
August 1, 1984
Subject Category
Composite Materials
Report/Patent Number
A-9844
NAS 1.15:86001
NASA-TM-86001
Accession Number
84N32438
Funding Number(s)
PROJECT: RTOP 505-33-21
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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