Structural Efficiency and Multi-Functionality of Well-Behaved Nonlinear Composite Structures

Composite materials and advanced structures are predicted to be major drivers for the growth and competitiveness of UK's value-added manufacturing economy. Maintaining and further enhancing the current national competitive advantage has been identified as a government strategic priority. This fellowship will contribute toward this goal by considering engineering structural design and composite materials in a different light.

When conceiving structures, it is common practice to rely on well-established design principles and robust analysis tools. This may be for several reasons, but the lack of experience with different approaches is probably the most important. Exploring the opportunities that are available outside the 'designer comfort zone' is a risky, expensive and time-consuming gamble that engineering companies can rarely afford to take.

History shows several examples of structural designs that, despite being at the forefront of current material technologies, missed out on remarkable engineering opportunities. The Iron Bridge, across the river Severn near Coalbrookdale, is probably the most famous case in point in Britain. Completed in 1779, the bridge was the world's first to be made of cast iron and is renowned for being substantially overdesigned, having been conceived following rules for wood rather than metal constructions. Composite materials are a modern example. One of their most remarkable features is the versatility that allows engineers to design not only a structure but also its constituent materials. However, partly due to their excellent specific stiffness, there is often the tendency to use them to replicate the well-known behaviour of isotropic materials, thus missing the opportunity to exploit many of the benefits that they could potentially provide. Owing to the colour of carbon fibre composites, this modus operandi is known as the 'black metal' approach. In a similar way, structural design is normally limited to linear regimes. In other words, structures are often designed to be stiff and exhibit small displacements, i.e. to respond linearly to the applied loads. Under these circumstances design methods are well established and based on decades of experience. This is indeed the engineer's comfort zone. Designers usually avoid large displacements because they may cause unwanted shape changes and trigger the transition to nonlinear regimes, potentially leading to catastrophic and often sudden, uncontrolled failure. However, if we could learn to control such behaviour, it could actually be exploited for a benefit.

The aim of this proposal is to explore the possibilities given by nonlinear responses in structural design. The principal objectives are the development of a new generation of adaptive/multifunctional structures working in elastically nonlinear regimes and the creation of novel paradigms for structural efficiency. The ambition is to harness the possibilities presented by composite materials and to deliver new design principles by removing the barriers imposed by the current practice of restricting structures to behave linearly. Imagine aircraft wings or wind turbine blades tailored to be lighter and still meet the requirements imposed at different operating conditions, thanks to nonlinear stiffness characteristics; buildings whose structural response is compliant only if subjected to extreme earthquake loads, so as to prevent catastrophic failure; or a bridge whose stiffness increases in case of strong winds preventing detrimental aeroelastic instabilities. This is my vision. This is what the elastic properties of composite materials can offer, if we move away from the 'black metal' approach.

The UK government has identified Advanced Materials as one of Eight Great Technologies to be promoted for the implementation of its industrial strategy. Furthermore, composite materials and advanced structures are considered key factors for the competitiveness, development and success of the UK economy. My proposal seeks to reach into new and unexplored areas of structural and composites design. The goal is to govern structurally nonlinear behaviours and to exploit them for a benefit.

I anticipate that exploiting well-behaved nonlinear composite structures will contribute to driving the growth of UK's value-added manufacturing economy. As a result of this fellowship novel cutting edge technology might be produced. An impact on the UK economy will be made if manufacturers will be able to exploit it to maintain or gain a competitive market positions. The most direct pathways to impact will be sought with ongoing involvement in the research of the parties that have indicated their interest with the Statements of Support. The current ACCIS (Advanced Composites Centre for Innovation & Science) and Engineering Faculty's industrial partners provide additional links. In due course, the support of the National Composites Centre can act as a catapult to project innovations towards higher Technology Readiness Levels and right into the manufacturing sector. Where possible, any potentially exploitable concept will be dealt with the help of the Bristol's Research and Enterprise Development (RED) office and protected with patenting and licensing mechanisms.

I will develop the design principles and the methodologies arising from this fellowship into a novel set of skills to be transferred to engineers and technical people. This new expertise might play a key role for British companies in creating the much sought competitive advantage. The University of Bristol and its Engineering Faculty are particularly well-positioned to convey novel skills, via the ACCIS Centre for Doctoral Training, the Industrial Doctorate Centre and their numerous industrial links. I intend to make the most of this position by organising annual workshops to share the results of the proposed research and to transfer the methods that will be developed.

A direct impact on the people's quality of life will derive from the development of novel standards for structural efficiency. Using less mass more effectively will indeed result in greener structures and vehicles, with an obvious advantage to the environment.

Delivering all of the aforementioned impacts would produce wealth and growth and consequently have a positive influence on wider society.