An experimental/analytical investigation of combined shear/end loaded compression strength testing of unidirectional composites

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dc.contributor.authorHahn, Steven Ericen
dc.contributor.committeechairReifsnider, Kenneth L.en
dc.contributor.committeememberHendricks, Scott L.en
dc.contributor.committeememberMook, Dean T.en
dc.contributor.departmentEngineering Mechanicsen
dc.date.accessioned2014-03-14T21:52:25Zen
dc.date.adate2009-12-23en
dc.date.available2014-03-14T21:52:25Zen
dc.date.issued1992-05-15en
dc.date.rdate2009-12-23en
dc.date.sdate2009-12-23en
dc.description.abstractThe Illinois Institute of Technology Research Institute (IITRI) composite compression test method is probably the most widely accepted as producing accurate results. Difficulties associated with the application of this method, however, have fueled continued research into alternate methods. In this study, the Wyoming End-Loaded Side-Supported (ELSS) test scheme was investigated in a combined shear/end loaded mode. This system was examined experimentally and analytically to establish the method as a reasonable alternative to IITRI testing. Combined shear/end loading was accomplished by applying a controlled amount of clamping force to the stabilizing blocks, allowing them to transmit shear force to the coupon faces through friction. The fabrication of test specimens from a BASF graphite IBMI material system is described in detail, including the application of a novel "press-clave" processing system developed at Virginia Tech. This system allows for cost-effective manufacture of flat panels under conditions similar to autoclave processing. For the material system employed in this study, this process proved superior to conventional hot press processing. Experimental results include strengths and failure modes for both tabbed and untabbed coupons tested by the combined loading ELSS method, and these data are compared to the results by the IITRI method. Strength was found to increase with increasing clamping, but reached a maximum with both untabbed and tabbed specimens. The maximum strength achieved with untabbed specimens was still significantly below the IITRI value, but the tabbed specimens reached strengths comparable to the IITRI data. The failure mode also changed with increased clamping, from end crushing to brooming with untabbed specimens, and from end crushing to shear failure with tabbed specimens. As the strength and failure mode achieved with the combined loading ELSS method using tabbed specimens are both similar to those seen in the IITRI tests, this modified technique can be considered equivalent to the IITRI method. Preliminary data from tests using novel nonbonded tabs were also similar to those given by the IITRI method. The finite element method was used to analyze the effect of increasing the clamping force. Competing effects of locally complex and severe stresses at the coupon end and a stress concentration which develops at the end of the gage section were shown to limit the maximum strength. Tabs appear to reduce the stress concentration while further decreasing the stresses at the end, allowing results comparable to those given by the IITRI method to be achieved.en
dc.description.degreeMaster of Scienceen
dc.format.extentxv, 380 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-12232009-020534en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12232009-020534/en
dc.identifier.urihttp://hdl.handle.net/10919/46404en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1992.H336.pdfen
dc.relation.isformatofOCLC# 26000751en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1992.H336en
dc.subject.lcshComposite materials -- Testingen
dc.subject.lcshShear (Mechanics)en
dc.titleAn experimental/analytical investigation of combined shear/end loaded compression strength testing of unidirectional compositesen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineEngineering Mechanicsen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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