Design of novel, additively manufactured cellular lattice supported composite structures using topology optimisation

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Upscaling the production of wind energy capacity is of great importance domestically and globally due to three significant factors. Firstly, pollution from greenhouse gases and other emissions as a result of burning fossil fuels for energy contributes to global warming. These effects cause increased instability of the climate, resulting in more natural disasters as well as ecosystem collapse. Secondly, over-dependence on fossil fuel for energy causes insecurity and tensions between and within nations. Thirdly, increasing the installed capacity of wind energy is an economic benefit. Wind energy is highly cost efficient for producing energy and the investment in the wind industry drives economic growth due to job creation in manufacturing, construction, and operation and maintenance. The development of new technology and energy storage networks also helps to lower costs of wind and other forms of renewable energy. One of the largest barriers to faster production of wind energy capacity is the cost and lead time of manufacturing wind turbine rotor blades. The growing scale of wind blades means that the main costs of manufacturing which are associated with materials, labour, and tooling, are a limiting factor. It is proposed that manufacturing a mould which acts as the internal structure of the blade would target each of these sources of cost through enabling automation and reduced material use by removing the need for expensive steel-backed composite moulds.Additive manufacturing (AM) is an enabling technology which is crucial for producing large scale structures in future. It's main function for wind blade production is more efficient use of material and division of labour. AM enables the use of topology optimisation (TO) for the design of large structures. TO provides a means to design structures for specific performance needs. AM allows for the creation of these structures that have been customized, making the two technologies an ideal match for producing structures that are designed to meet specific needs. The combination of TO and AM leads to the creation of structures that are highly efficient with minimal waste and maximum speed in production.There are two main challenges associated with using topology optimisation in wind blade design. Firstly, the aeroelastic response of the blade is an important factor in the structural design, as it can improve the blade's ability to capture energy from the wind and alleviate loads by optimising the stiffness and tuning the natural frequencies. Topology optimisation is not readily compatible with aeroelastic solvers and there is limited research combining aeroelastic design with topology optimisation due to this difficulty. Secondly, composite laminates are critical component of large wind turbine blades, due to the size of the bending moment arms. Topology optimisation of orthotropic laminates and multiple materials is limited in its ability to design large scale, manufacturable structures, given the computationally intensive process.A design methodology is proposed, which leverages the strengths of topology optimisation and additive manufacturing to achieve optimised composite laminate configurations as well as repeated unit cell graded lattice architectures for wind turbine blades. The method involves a multi-stage topology optimisation process; In the first stage, a composite laminate structure is designed based on an idealised topology optimisation solution; In the second stage, the results from the first stage are frozen and utilised to design a 3D printed repeated unit cell architecture which supports the composite laminates and allows for improved manufacturability. The goal of this process is to combine conventional knowledge of structural requirements for efficient use of composite laminate configurations, while also enabling the inclusion of additive manufacturing to support and improve performance, weight and manufacturing cost.