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Fatigue damage development and failure in unidirectional and angle-ply glass fibre/carbon fibre hybrid laminates
2000 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

With increased dimensions of composite structures, it has become useful to add strong carbon fibres to glass-fibre reinforced plastics to maintain low deflections. In rotor blades for wind turbines, for instance, hybrid designs with glass/carbon fibre rein-forced plastics are under consideration as the blades are getting larger than 30-40 me-tres. The tensile fatigue behaviour of unidirectional [02]4s and angle-ply [±10]4s and [±45]4s glass fibre/carbon fibre hybrid composites has been investigated. Dynamic measurements of mechanical properties were carried out during the fatigue process. The temperature field evolution of the specimen surface in an insulated testing chamber was monitored by thermovision. The hysteresis energy loss correlates well with the tem-perature. The accumulation of damage was quantified as the difference between the me-chanical hysteresic loss and the heat dissipated through radiation, convection and con-duction. Microscopic studies show frictional sliding of longitudinal crack faces between carbon and glass fibre bundles to be the main source of dissipation for on-axis specimen. With increasing off-axis angle the primary loss mechanism was inelastic shear deforma-tion of the polymer matrix. For larger off-axis angle, a higher fatigue sensitivity was observed. A misalignment of a fibre leads to a more energy consuming crack propaga-tion involving fibre bridging, which results in a more fatigue resistant material. With a finer dispersion of the constituents of the hybrid, the growth of the longitudinal cracks or zones of matrix inelastic shear deformation would be suppressed to provide more fatigue resistant material. A localisation of heat generation sets in just prior to final failure. Damage and heat localisation lead to imminent failure. If the parameters that control localisation were better understood, it would be possible to improve the fatigue resistance of the material by sensible microstructural design.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Fatigue, composites, hybrid, damage, heat dissipation, tensile, behaviour
Keyword [sv]
URN: urn:nbn:se:ltu:diva-59435ISRN: LTU-EX--00/064--SELocal ID: ff5e37c5-72b4-42e8-84fe-237f86dea59dOAI: diva2:1032823
Subject / course
Student thesis, at least 30 credits
Educational program
Civil Engineering programmes 1997-2000, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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