General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Optimisation of Composite Structures -Enforcing the Feasibility of Lamination Parameter constraints with Computationally-efficient Maps AbstractComposite materials are increasingly used in high performance structural applications because of their high strength and stiffness to weight ratios together with their significant tailoring capabilities. The stiffness of a monolithic laminate can be expressed as a linear combination of material invariants, one thickness variable, and twelve lamination parameters, which is an efficient alternative to using fibre angles as design variables. However, feasibility constraints originating from the interdependency between lamination parameters must be satisfied to obtain laminates with realistic stiffness properties. Currently, enforcing these feasibility constraints is a computationally intensive task. In this paper we propose to use normalised design variables that inherently map (i.e. correspond) to feasible lamination parameters, effectively removing the need to evaluate feasibility constraints altogether. To this end, linear and B-spline maps of the feasible lamination parameter subspace are proposed and evaluated. Results of 2D and 4D benchmark analyses and optimisation studies suggest that the proposed methodology does successfully provide an efficient means of achieving feasible results at lower computational costs.

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We propose a new optimisation framework developed for the investigation of innovative wind turbine blade designs. The design of wind turbines has progressively evolved over recent decades as part of an ongoing effort to provide economically competitive solutions for wind energy production. In particular, rotors have increased in size so as to capture more wind energy while limiting installation costs. At the same time blade designers have had to continually improve the structural efficiency of blades in order to accommodate higher extreme and fatigue loads resulting from growing rotor diameters. Modern wind turbine designs are the result of these incremental improvements, limiting financial risks but also confining the design space and effectively reducing opportunities for more radical innovation. In this paper, we enable the wider exploration of the wind turbine blade design space by means of a new optimisation framework. For that purpose we develop and combine state-of-the-art tools for the aero-servo-elastic analysis and optimisation of wind turbines aiming to explore the uncharted design space resulting from decades of incremental changes. Our framework relies on the use of B-spline surfaces and lamination parameters to provide a compact and continuous means of describing blade structures, also enabling the use of gradient-based optimisers. This structural parameterisation is further combined with beam and shell finite element models to provide further confidence in preliminary structural designs. The proposed framework is presented and verified herein. Validation results show good agreement with the modern large scale DTU 10 MW blade design. Additionally, the coupled bend-twist behaviour of the beam model is found to agree well with higher fidelity finite element model predictions.