Charakterisierung der Schadenstoleranz und der monotonen und zyklischen interlaminaren Risszähigkeit von Polymer-Laminaten

Translated title of the contribution: Characterization of the damage tolerance and the monotonic and cyclic interlaminar fracture toughness of fibre reinforced composite laminates

Steffen Stelzer

Research output: ThesisMaster's Thesis

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Abstract

High performance fibre composites feature outstanding specific properties and therefore have an indisputable potential for applications in lightweight design. Nevertheless their application is limited especially because of their susceptibility to delamination. Delaminations can grow to a critical size under cyclic loading conditions, even at loads below the static strength of the material and can thus trigger the failure of the structure. To be able to avoid such a failure one has both to create key figures to describe the initiation and growth of delaminations for design purposes and to find approaches for the enhancement of the material performance. Besides restricting the growth of the delaminations through adequate steps in processing, one major aspect has to be the behavior of these materials under impact loads, because these are, together with cyclic loads, the most critical loads for fibre reinforced composites with a layer composition. Both loading conditions are part of the damage tolerance concept. This thesis dealt with both aspects, considering different materials. Cyclic delamination testing carried out under displacement control proved to be an appropriate tool to measure the growth of delaminations from artificial and well-defined defects in unidirectional (UD) laminates. The delamination behavior of UD-laminates with matrices made of either polyetheretherketone or epoxy resin could be well compared and influences of neither machine parameters, nor specimen parameters on the measurements could be found. The duration of the tests were limited to 24 hours to make them appicable to an industrial surrounding. The focus of the measurements was put on the comparison of the crack growth curves, without considering the threshold region. Furthermore the delamination behavior of braidings with bi- and triaxial layups was investigated. For monotonic as well as for cylic loading no significant difference between these layups could be found. To assess both the residual strength of the braidings after a damage with a defined impact energy and the degree of damage, compression after impact measurements were carried out. Thereby it was found, that the 45/90/-45 and the +/-45 layup, respectively the 45/0/-45 and the 0/90 lay-up showed a similar compression strength after impact.
Translated title of the contributionCharacterization of the damage tolerance and the monotonic and cyclic interlaminar fracture toughness of fibre reinforced composite laminates
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Pinter, Gerald Gerhard, Supervisor (internal)
Award date18 Dec 2009
Publication statusPublished - 2009

Bibliographical note

embargoed until null

Keywords

  • fatigue delamination unidirectional laminate fracture toughness damage tolerance braiding

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