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| Volume 3, Issue 03 - 2007 |
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| 3 |
STIFFNESS DEGRADATION MONITORING OF CARBON NANOTUBE DOPED GLASS / VINYLESTER COMPOSITES VIA RESISTANCE MEASUREMENTS |
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| Pages 90-95 |
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| GEORGE SOTIRIADIS1, panagiota tsotra1, ALKIVIADIS PAIPETIS2, VASSILIS KOSTOPOULOS1 |
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1 Applied Mechanics Laboratory, Mechanical Engineering Dept, University of Patras, Greece
2 Dept of Materials Science & Engineering, University of Ioannina, Greece |
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| Received 23 May 2007; accepted 24 July 2007 |
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| Multi wall carbon nanotubes (CNTs) were used as an additive in the matrix of glass / vinylester composites in order to improve their damage tolerance and provide a means for their damage assessment at any stage of their loading history. The improvement of the damage tolerance is expected to stem from the incorporation of an additional interfacial area that activates energy dissipation mechanisms. These mechanisms include interfacial sliding, fibre pull out and bridging as well as crack bifurcation and arrest and are active at shear perturbations at the nanoscale. On the other hand, the life monitoring is performed via the measurement of the electrical resistance changes in the conductive carbon nanotube network within the composite matrix; this network follows any deformation of the composite providing real time strain monitoring whereas, at the same time, pinpoints all loci of failure; this is performed because of the local breach of the conductive path that the CNTs form that leads to a monotonic increase in the overall resistance. The experimental findings verify both the increased damage tolerance of the doped composites and the reliable damage assessment of the composite at all stages of its loading history. The modified composites exhibit improved damage tolerance in tensile cyclic loading by approximately 25% compared to the conventional composites. The electrical resistance is following the real time deformation and at the same time exhibits a monotonic increase directly related to the stiffness reduction of the composite. The SEM fractographic examination of the fracture surfaces of the CNT dopes composites revealed a fair dispersion of the CNTs in the matrix, indicating that further improvement in the damage tolerant behaviour is feasible. |
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