The continual need to better aircraft performance is increasingly prompting designers towards the realisation of morphing structures. One such enabling morphing technology are "multistable composites", and interest in them stems from the fact that they are able to sustain significant changes in shape without the need for a continuous power supply. This research benefits from the tow-steering technique to develop laminates with curved fibre-paths or Variable Angle Tows (VAT) in a ply (i.e. exploiting the anisotropy of composites), to introduce residual thermal stresses capable of imparting bistability. The principle idea is that VAT laminates can impart bistability with the new feature of ensuring fibre continuity within the wider structure facilitating structural integration (i.e. blending of lay-ups across components). Additional structural strength is shown to be imparted due to the load path continuity achieved via the tow-steering technique. The thermally induced bistable behaviour of VAT laminates is investigated through Finite Element (FE) modelling and experimental studies. The effect on the stable shapes for variations in the resin layers, fibre volume fraction (Vf), resin thermal expansion and laminate thickness are reported and found to be influential (from high to low) in the same quoted order. An approach, aiding the development of well- defined finite element models that are capable of predicting the bistable behaviour of manufactured laminates, is presented. It is shown that despite the inherent variabilities in laminates, a shell model capturing sufficient detail (i.e. resin layer[s), ply thicknesses and the Vf of a ply) is successful in predicting the cured shape(s). An optimisation based design framework aimed at realising the morphing potential of VAT laminates is presented. A morphing alternative to the plain flap is achieved, and the two potential solutions: one aiming to maximise the deployed flap-angle, and the other to attain maximum flap-angle increment, are discussed. Moreover, a good agreement exists between the FE predictions and the experimental observations for the manufactured laminates, demonstrating the feasibility of the morphing flap concept.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:574264 |
| Date | January 2012 |
| Creators | Panesar, Ajit S. |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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