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Archivio digitale delle tesi discusse presso l’Università di Pisa

Tesi etd-09072006-165749


Tipo di tesi
Tesi di laurea specialistica
Autore
Profeta, Fulvio Paolo
Indirizzo email
fulviopaoloprofeta@virgilio.it
URN
etd-09072006-165749
Titolo
MECHANICAL PROPERTIES OF HYBRID COMPOSITE LAMINATES - Management of failure modes in Z-pinned composite structures
Dipartimento
INGEGNERIA
Corso di studi
INGEGNERIA CHIMICA
Relatori
Relatore Partridge, Ivana K.
Relatore Prof. Lazzeri, Andrea
Parole chiave
  • composites
  • delamination
  • impact
  • lap-joints
  • Z-pinning
Data inizio appello
11/10/2006
Consultabilità
Parziale
Data di rilascio
11/10/2046
Riassunto
The thesis presents results of quasi-static tensile tests of thin-walled, patch-joined, butted I-sections manufactured from woven carbon fabric (T300/914).
The work concentrates on the performance of z-pins as a means of strengthening a lap joint between two carbon fibre reinforced polymer composites (CFRP) I-sections placed end-to-end. These I-section test joints have been tested under tensile load in an attempt to best mimic the loading conditions of a representative aerospace structure.
For the benefit of this work the author has attempted to produce a failure map for the joint in question, incorporating the effects of overlap length and z-pin reinforcement on the load capability of the joint.
The effect of through-the-thickness reinforcement (TTR) by Z-pinning of the patch on the maximum load is minimal, but the failure mode changes from patch delamination to a laminate failure in the flanges and the web of the I-section. The delamination limiting effect of the Z-pinning is also seen in post-impact tensile tests on similar I-sections. The thesis examines also the relationships between the macromechanics of the failure of the I-sections and the micromechanics of failure of Z-pinned laminates.
The failure management consists of adjusting the various joint geometries to induce the wanted failure mode. The results presented show that Z-pinning is effective in retarding or stopping delamination crack propagation and its use can in some cases lead to a slightly increased joint failure load. There is a knock down in tensile strength for the Z-pinned laminates which is seen for the joints which fail in the laminate. The post impacted joints which fail in the laminate do not display this knock-down suggesting a damage tolerance improvement through the use of Z-pins.
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