Abstract
This thesis describes the experimental and finite element studies undertaken to develop a piezoelectrically actuated morphing structure based on bistable composite laminates. An adaptive bump mechanism is proposed as a demonstrator and the need for robust finite element models of bistable composites, Macro Fibre Composite (MFC) actuators and morphing structures combining these two technologies are identified as key research objectives. The developed models will be used to predict laminate deformation and actuation behaviour.Laminate deformation and shape for both deformation states of bistable laminates is accurately predicted to within 12.5% by a finite element model including measured ply thickness data. The observed deformation states exhibit approximately opposing cylindrical curvatures about different axes of curvature. Regions of localised curvature reversal within bistable composite structures are also predicted by the model and these effects are correlated with variations in the through thickness stress components.
The actuation capability of a piezoelectric MFC actuator is predicted by finite element analysis, creating a homogenised solid model that includes three-dimensional compliance, dielectric and piezoelectric matrices. Prediction of actuation capability and changes in actuator compliance caused by changing electrical boundary conditions are in excellent agreement with experimental measurement.
The developed finite element models for bistable laminates and MFC actuators are combined to predict the cured shape and snap-through voltage of two MFC actuated cross ply bistable laminates. Predicted snap-through voltage agrees with experimental measurements to within 5%.
Laminate deflection induced by changes in ambient temperature is measured to examine the influence of temperature dependent elastic constants and coefficient of thermal expansion of epoxy resin on laminate deflection. Additionally, the blocking force, free-deflection and deflection creep-rate for an MFC-actuated bistable laminate are experimentally characterised to determine operational actuation capabilities.
Finally, a finite element model based on insights gained in the preceding work is used to design an adaptive bump. Qualitative prediction of device behaviour and prediction of cured shape for the resulting prototype design are both excellent; however snap-through voltage is less well modelled by the presented work.
| Date of Award | 1 Aug 2010 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Chris Bowen (Supervisor) & Hyunsun Kim (Supervisor) |
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