Conventional composites such as carbon fibre reinforced plastics have outstanding mechanical properties: high strength and stiffness, low weight, and low susceptibility to fatigue and corrosion. Composites are truly the materials of the future, their properties can be tailored to particular applications and capabilities for sensing, changing shape or self healing can also be included. Their use is rising exponentially, continuing to replace or augment traditional materials. A key example is the construction of new large aircraft, such as the Boeing 787 and Airbus A350, mainly from carbon fibre composites. At the same time, there is rapid expansion of composite use in applications such as wind turbine blades, sporting goods and civil engineering infrastructure.Despite this progress, a fundamental and as yet unresolved limitation of current composites is their inherent brittleness. Failure is usually sudden and catastrophic, with little or no warning or capacity to carry load afterwards. A related problem is their susceptibility to impact damage, which can drastically reduce the strength, without any visible warning. Structures that look fine can fail suddenly at loads much lower than expected. As a result complex maintenance procedures are required and a significantly greater safety margin than for other materials. Our vision is to create a paradigm shift by realising a new generation of high performance composites that overcome the key limitation of conventional composites: their inherent lack of ductility. We will design, manufacture and evaluate a range of composite systems with the ability to fail gradually, undergoing large deformations whilst still carrying load. Energy will be absorbed by ductile or pseudo-ductile response, analogous to yielding in metals, with strength and stiffness maintained, and clear evidence of damage. This will eliminate the need for very low design strains to cater for barely visible impact damage, providing a step change in composite performance, as well as overcoming the intrinsic brittleness that is a major barrier to their wider adoption. These materials will provide greater reliability and safety, together with reduced design and maintenance requirements, and longer service life. True ductility will allow new manufacturing methods, such as press forming, that offer high volumes and greater flexibility.To achieve such an ambitious outcome will require a concerted effort to develop new composite constituents and exploit novel architectures. The programme will scope, prioritise, develop, and combine these approaches, to achieve High Performance Ductile Composite Technology (HiPerDuCT).

Among technically and economically viable renewable energy sources, wind power is that which exploitation has been growing fastest in the recent years. This research focuses on modern Horizontal Axis Wind Turbines (HAWT's), which typically feature two- or three-blade rotors. The span of HAWT blades can vary from a few meters to more than 100 meters, and their design is a complex multidisciplinary task which requires consideration of strong unsteady interactions of aerodynamic and structural forces. Some of the most dangerous sources of aerodynamic unsteadiness are a) yawed wind, due to temporary non-orthogonality of wind and rotor plane, and b) blade dynamic stall. These phenomena result in the blades experiencing time-varying aerodynamic forces, which can excite undesired structural vibrations. This occurrence, in turn, can dramatically reduce the fatigue life of the blades and their supporting structure, yielding premature mechanical failures. Events of this kind can compromise the technical and financial success of the installation, which heavily relies on fulfilling the expectations of minimal servicing on time-scales of the order of 10 to 30 years. These facts highlight the importance of the aeroelastic design process of HAWT blades. The unsteady aerodynamic loads required to determine the structural response must be understood and accurately quantified in the development phase of the turbine. Due to the sizes at stake, in most cases it is infeasible to perform aeroelastic testing, not only from an economic but also logistic viewpoint. Hence these aeroelastic issues can only be tackled by using accurate simulation tools.The general motivation of this project is two-fold: it aims both at enriching the knowledge of unsteady flows relevant to wind turbine aeroelasticity, and advancing the state-of-the-art of the computational technology to accomplish this task. These objectives are pursued by using a novel Computational Fluid Dynamics (CFD) approach to wind turbine unsteady aerodynamics. The unsteady periodic flow relevant to aeroelastic analyses is determined by solving the three-dimensional unsteady viscous flow equations with the nonlinear frequency-domain (NLFD) technology. The NLFD-CFD approach has been successfully applied to fixed-wing and turbomachinery aeroelasticity. This research will exploit this high-fidelity methodology to enhance the understanding of the severe unsteady aerodynamic forcing of HAWT blades, and substantially reduce computational costs with respect to conventional time-domain CFD analyses. This method is particularly well suited to investigate the unsteady aerodynamic blade loads associated with stall-induced vibrations and yawed wind. On the other hand, this technology will greatly help designers to develop new blades without relying on the database of existing airfoil data on which the majority of present analysis and design systems depend. One of the main results of this project will be to greatly reduce the dichotomy between the conflicting requirements of physical accuracy and computational affordability of the three-dimensional unsteady viscous flow models for wind turbine unsteady aerodynamics and aeroelasticity. The achievements of this research will benefit the British and European industry in that they will offer an effective tool to design more efficient and reliable blades. The NLFD-CFD technology will also provide deeper insight into unsteady aerodynamic phenomena which affect the fatigue life of wind turbines. In the next few years, the certification process of wind turbines will enforce stricter requirements on the industry. The developed technology will support the analyses required to meet enhanced certification standards. The Unsteady Aerodynamics Research Community as a whole will also benefit from this research, because its findings will enhance and consolidate the deployment of the NLFD technology in rotorcraft, turbomachinery, and aircraft aeroelasticity.

Composites are now widely used in a wide range of applications. In the wind turbine and aerospace sectors recent innovations, including larger and more sophisticated structures, have driven the need for better understanding of failure of composite structures. Use of lower-cost process routes requires a need for better understanding of the inevitable defects in such composite structures. Failure of well-controlled flat composite panels is now generally well understood. However real manufactured components contain a range of stress concentrators, some associated with relatively controlled features such as joints, ply drops, sandwich panel closures and holes, some more uncertain associated with defects including fibre waviness, resin-rich areas and gaps at sandwich core breaks. The aim of the project is to understand and model how such defects affect the strength of the structure.The project has three main strands: (i) characterising realistic defects in industrial components and in controlled laboratory specimens, (ii) identifying mechanisms of compressive failure under fatigue loading and developing predictive models for failure at waviness defects, validated with experiments, (iii) modelling of defect formation during processing. Case studies suggested by industrial partners Dowty and Vestas of a propeller and a wind turbine blade will be used. The models will be incorporated into software tools, in collaboration with Simulayt Ltd, for use in design.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

This proposal is for the renewal of the block grant for the Engineering Innovative Manufacturing Centre at the University of Bath. The Centre is unique in combining a design focus with a strong emphasis on manufacture in a closely integrated group. The context of the Centre's work is:* globally distributed design and manufacture of complex products and processes;* pressure on price, quality and timescale;* the move from test-based (physical prototypes) to simulation-based (virtual prototypes) engineering* the movement towards sustainable engineering practice. * the key importance in engineering of knowledge and information management. The Bath Engineering IMRC's mission is to develop tools, methods and knowledge, underpinned by appropriate theory and fundamental research, to support engineering enterprises in these new circumstances. In particular, the focus of the Centre is on whole life design information and knowledge management, and improving the design of machines, processes and systems.