Effect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminates

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dc.contributor.authorSubramanian, Sureshen
dc.contributor.committeechairStinchcomb, Wayne W.en
dc.contributor.committeememberKander, Ronald C.en
dc.contributor.committeememberKriz, Ronald D.en
dc.contributor.committeememberLoos, Alfred C.en
dc.contributor.committeememberReifsnider, Kenneth L.en
dc.contributor.departmentEngineering Science and Mechanicsen
dc.date.accessioned2014-03-14T21:08:54Zen
dc.date.adate2008-01-25en
dc.date.available2014-03-14T21:08:54Zen
dc.date.issued1994-01-01en
dc.date.rdate2008-01-25en
dc.date.sdate2008-01-25en
dc.description.abstractA systematic study was conducted to examine the influence of fiber surface treatment and sizing on the formation of fiber-matrix interphase and its effects n the mechanical properties of composite laminates. Three material systems having the same Apollo graphite fibers and HC 9106-3 toughened epoxy matrix, but with different fiber surface treatments and sizings were used in this study. The fibers used in the 810A and 820 A systems received 100% and 200% industry standard surface treatments respectively and were sized with Bisphenol-A unreacted epoxy material. The 810 O system was manufactured with 100% surface treated fibers that were sized with pvp (polyvinylpyrrolidone), a thermoplastic material. The presence of different interphase in these materials was confirmed using a permanganic etching technique. Results indicate that the interphase is discontinuous and made of linear chain polymeric material in the 810 A system. The interphase in the 810 O system has a gradient morphology while the 820 A system does not possess a well defined interphase. Mechanical test results indicate that the 810 O system significantly greater longitudinal tensile strength and failure strain compared to the 810 A system. The 810 A and 820 A systems have similar longitudinal tensile properties. Transverse tensile test results indicate that the 820 A system has the highest strength while the 810 O system has the lowest strength. The (0,90₃), cross-ply laminates from the three material systems exhibit different damage mechanisms and failure modes under monotonic tensile loading. Fatigue test results indicate that the 810 O laminates have longer fatigue lives at higher load levels and shorter fatigue lives at lower load levels compared to the 810 A laminates. The 820 A laminates have longer life compared to the other two materials systems, at all three load levels. The 810 O material exhibits greater damage and stiffness reduction than the other two materials. The 810 A and 820 A systems exhibit a brittle stress concentration controlled failure, while the pvp sized 810 O system exhibits a global strain conuolled failure. A micromechanics model was developed to investigate the role of the interphase on the tensile strength of unidirectional laminates. A new parameter called the ‘efficiency of the interface’, is introduced in the model. A simple scheme that uses the experimentally determined tensile modulus of unidirectional laminates in a concentric cylinders model, is described to estimate the interfacial efficiency. The tensile fatigue performance of cross-ply laminates is predicted using this micromechanics model in a cumulative damage scheme. The predicted fatigue lives and failure modes agree well with experimental results.en
dc.description.degreePh. D.en
dc.format.extentxv, 231 leavesen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-01252008-165523en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-01252008-165523/en
dc.identifier.urihttp://hdl.handle.net/10919/37216en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1994.S837.pdfen
dc.relation.isformatofOCLC# 31228851en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectthermoplasticsen
dc.subject.lccLD5655.V856 1994.S837en
dc.subject.lcshFibrous composites -- Mechanical propertiesen
dc.subject.lcshGraphite fibers -- Surfacesen
dc.subject.lcshLaminated materials -- Mechanical propertiesen
dc.titleEffect of fiber/Matrix Interphase on the Long Term Behavior of Cross-Ply Laminatesen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineEngineering Science and Mechanicsen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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