Instability-related delamination growth of embedded and edge delaminations

dc.contributor.authorWhitcomb, J. D.en
dc.contributor.committeechairReifsnider, Kenneth L.en
dc.contributor.committeememberReddy, Junuthula N.en
dc.contributor.committeememberRaju, I.S.en
dc.contributor.committeememberSmith, Charles W.en
dc.contributor.committeememberFarkas, Dianaen
dc.contributor.departmentMaterials Engineering Scienceen
dc.date.accessioned2017-05-24T18:18:57Zen
dc.date.available2017-05-24T18:18:57Zen
dc.date.issued1988en
dc.description.abstractCompressive loads can cause local buckling in composite laminates that have a near-surface delamination. This buckling causes load redistribution and secondary loads, which in turn cause interlaminer stresses and delamination growth. The goal of this research effort was to enhance the understanding of this instability-related delamination growth in laminates containing either an embedded or an edge delamination. There were three primary tasks: 1) development of a geometrically nonlinear finite element analysis named NONLIN3D; 2) performance of a parametric analytical study to determine the effects of strain, delamination shape, and delamination size on the distribution of the strain energy release rate components along the delamination front; and 3) performance of a combined experimental and analytical study of instability-related delamination growth (IRDG). Two material systems (AS4/PEEK and IM7/8551-7) and two stacking sequences (0/90/90/0)₆ and (90/0/0/90)₆ were examined. The laminates were fabricated with Kapton inserts between the fourth and fifth plies from the top surface to give an initial delamination. The analysis predicted a large variation of G<sub>I</sub> and G<sub>II</sub> along the delamination front. The G<sub>III</sub> component was always small. The location of maximum G<sub>I</sub> and G<sub>II</sub> depended on the delamination shape and applied strain. In general, the strain-energy release rates were small except in a small region. Hence, delamination growth was expected to occur over only a small portion of the delamination front. Experiments corroborated this prediction. The laminate stacking sequence had a large effect on the shape of the deformed region, the direction of delamination growth, and the strain at which delamination growth occurred. These effects were predicted by the analysis. The G<sub>I</sub> component appeared to govern initial delamination growth in the IM7/8551-7 laminates. Matrix ply cracking generally accompanied delamination growth. In some cases fiber micro-buckling also occurred shortly after delamination growth occurred.en
dc.description.degreePh. D.en
dc.format.extentvi, 194 leavesen
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttp://hdl.handle.net/10919/77755en
dc.language.isoen_USen
dc.publisherVirginia Polytechnic Institute and State Universityen
dc.relation.isformatofOCLC# 18367889en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1988.W444en
dc.subject.lcshComposite materialsen
dc.subject.lcshFracture mechanicsen
dc.subject.lcshLaminated materialsen
dc.titleInstability-related delamination growth of embedded and edge delaminationsen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineMaterials Engineering Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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