Arresting and self-healing cracks
17 July 2008
Materials that can stop a crack and then self-heal have been brought a step closer to reality thanks to a new project launched by the University of Bristol and Imperial College London.
The Crack Arrest and Self-Healing in Composite Structures (CRASHCOMPS) project will be funded over four years with a £1.2 million grant from the Engineering and Physical Sciences Research Council and the Defence Science and Technology Laboratory.
The team's research will focus on carbon fibre polymer composites - materials made by combining extremely stiff and strong fibres with polymers to create strong, durable and lightweight materials. These are particularly important in the aerospace and transport industries, which use carbon fibre composites to make aircraft wings, helicopter rotor blades and ship hulls.
However, use and development of composites has been limited by concerns that they are susceptible to defects and damage. Dr Emile Greenhalgh from Imperial College London’s Composites Centre explains that because of this, current applications use excessively heavy parts, which leads to higher fuel consumption:
“Because engineers are worried about cracks forming in composites, they currently build many aircraft parts much stronger, and therefore heavier, than may be necessary, so they can withstand a 40% loss in strength during use. This means more fuel is needed to get them off the ground and flying to their destinations, which is far from ideal, in terms of aviation’s impact on the environment,” he said.
The aim of the new research project is to develop tailor-made composite materials which arrest the development of cracks, and heal themselves, which could be used with confidence to build lightweight, safe, damage-resistant components for more fuel-efficient aircraft, trains, cars and ships.
To achieve this, the team at Imperial will introduce materials which will deflect the path of the crack, and absorb the fracture energy associated with it. Once the crack has been arrested, the team at University of Bristol will utilise materials which ‘bleed and clot’, healing the crack and recovering much of the original material strength.
Dr Ian Bond from the University of Bristol’s Advanced Composites Centre for Innovation and Science, adds: “Nature provides a great deal of inspiration for how we can better engineer high performance structures. In addition to strength and stiffness, attributes such as toughness and self-healing are widely found throughout the range of biological materials, many of which are composites. This project will seek to understand and implement a variety of innovative and bio-inspired approaches to deliver a breakthrough in the performance of advanced composite materials.”
The new funding will also enable a free annual CRASHCOMP workshop, held at Bristol and Imperial on alternate years, providing a forum for researchers and industry to review the results and contribute to the direction of the programme.