Interlaminar stress analysis of dropped-ply laminated plates and shells by a mixed method

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dc.contributor.authorHarrison, Peter Newtonen
dc.contributor.committeechairJohnson, Eric R.en
dc.contributor.committeememberHaftka, Raphael T.en
dc.contributor.committeememberKapania, Rakesh K.en
dc.contributor.committeememberHyer, Michael W.en
dc.contributor.committeememberGürdal, Zaferen
dc.contributor.departmentAerospace Engineeringen
dc.date.accessioned2014-03-14T21:20:46Zen
dc.date.adate2005-10-10en
dc.date.available2014-03-14T21:20:46Zen
dc.date.issued1994-04-22en
dc.date.rdate2005-10-10en
dc.date.sdate2005-10-10en
dc.description.abstractA mixed method of approximation based on Reissner's variational principle is developed for the linear analysis of interlaminar stresses in laminated composites, with special interest in laminates that contain terminated internal plies (dropped-ply laminates). Two models are derived, one for problems of generalized plane deformation and the other for the axisymmetric response of shells of revolution. A layerwise approach is taken in which the stress field is assumed with an explicit dependence on the thickness coordinate in each layer. The dependence of the stress field on the thickness coordinate is determined such that the three-dimensional equilibrium equations are satisfied by the approximation. The solution domain is reduced to one dimension by integration through the thickness. Continuity of tractions and displacements between layers is imposed. The governing two-point boundary value problem is composed of a system of both differential and algebraic equations (DAEs) and their associated boundary conditions. Careful evaluation of the system of DAEs was required to arrive at a form that allowed application of a one-step finite difference approximation. A two-stage Gauss implicit Runge-Kutta finite difference scheme was used for the solution because of its relatively high degree of accuracy. Patch tests of the two models revealed problems with solution accuracy for the axisymmetric model of a cylindrical shell loaded by internal pressure. Parametric studies of dropped-ply laminate characteristics and their influence on the interlaminar stresses were performed using the generalized plane deformation model Eccentricity of the middle surface of the laminate through the ply drop-off was found to have a minimal effect on the interlaminar stresses under longitudinal compression, transverse tension, and in-plane shear. A second study found the stiffness change across the ply termination to have a much greater influence on the interlaminar stresses. Correlations between the stiffness ratio of the thick to the thin sections of the laminates and the magnitude of a parameter based on a quadratic delamination criterion were found to be surprisingly good for longitudinal compression and in-plane shear loadings. For laminates with very stiff terminated plies loaded in longitudinal compression, inclusion of a short insert of softer composite material at the end of the dropped plies was found to significantly reduce the interlaminar stresses produced.en
dc.description.degreePh. D.en
dc.format.extentxiii, 159 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-10102005-131618en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10102005-131618/en
dc.identifier.urihttp://hdl.handle.net/10919/39735en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1994.H377.pdfen
dc.relation.isformatofOCLC# 30964743en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V856 1994.H377en
dc.subject.lcshLaminated materials -- Testingen
dc.subject.lcshShells (Engineering)en
dc.subject.lcshStrains and stressesen
dc.titleInterlaminar stress analysis of dropped-ply laminated plates and shells by a mixed methoden
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineAerospace Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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