Bridging the scales: from the toughness of small specimens to the damage tolerance of large aerospace panels

The introduction of Carbon Fibre Reinforced Plastics (CFRP) for major structural parts in commercial aircraft leads to the need to predict the mechanical response, including failure and damage tolerance for these materials. The difficulty in predicting accurately failure and damage tolerance lies both on the complexity of the failure processes and in the scale at which they occur. In fact, the scales at which failure must be analysed (micro meters) are much smaller than the typical aerospace component scale (metres), and it is well known that strength and toughness depend on component size.This proposal will address the above, by focusing on three challenges. Firstly, the project will assess how tough these composites are at opposing the propagation of cracks which break entire panels (mixed mode translaminar fracture toughness). In continuation, the failure processes will be looked at in detail, so that suitable micromechanical models may be developed. Finally, the project will focus on developing computer codes which will assist Engineers in more effectively designing composite components.

The research to be carried out in this project will have a significant impact on how failure processes in composites are regarded, and is therefore expected to have a significant impact in the academic community. This project offers a significant potential for weight reduction in structural applications, by better exploiting the mechanical response of composites. This is of upmost significance for transport applications, including aeronautics and military. The environmental benefits that stem from the reduced fuel emissions associated with lighter structures constitute a compelling reason for the society's interest composite structures for transport applications. For carriers, the lower fuel consumption leads to enhanced economical competitively. Additionally, for military applications, lower structures lead to increased fuel autonomy, and concomitant increased safety as re-fuelling can take place further away from dangerous areas. The challenge addressed by Bridging the Scales can also be translated as an economical opportunity for UK's large composites-related industry - companies which are better equipped to design with composites will naturally flourish, but also will their suppliers. Industry too realises that they have a strong need for better design tools with composites, with Aerospace leading the way.