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

Lead Research Organisation: Imperial College London
Department Name: Dept of Aeronautics

Abstract

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.

Planned Impact

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.
 
Description - numerically-efficient failure models for large composite components
- new characterisation method for mode-II translaminar fracture toughness
Exploitation Route others can use the models or use the tests to characterise their materials.
Sectors Aerospace, Defence and Marine,Leisure Activities, including Sports, Recreation and Tourism,Manufacturing, including Industrial Biotechology,Transport

URL http://wwwf.imperial.ac.uk/aeronautics/research/pinholab/
 
Description Others can use the models or use the tests to characterise their materials. In addition, the insights into translaminar toughness that came for this project has been extremely important in motivating a considerable amount of research, both in my group (e.g. my EPSRC fellowship) and the ITN FibreMod) and elsewhere (the number of labs around the world using variations of CT tests to analyse translaminar fracture is growing by the day).
First Year Of Impact 2014
Sector Aerospace, Defence and Marine,Leisure Activities, including Sports, Recreation and Tourism,Manufacturing, including Industrial Biotechology,Transport
Impact Types Economic

 
Description EPSRC Research Fellowship for Growth
Amount £1,118,616 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 12/2014 
End 11/2019
 
Description MARIE SKLODOWSKA-CURIE ACTIONS Innovative Training Networks (ITN) Call: H2020-MSCA-ITN-2016
Amount € 3,370,807 (EUR)
Funding ID Marie Sklodowska-Curie grant agreement No 722626 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 10/2016 
End 09/2020
 
Title Computer models for failure of composite materials 
Description This model consists of: - several new failure criteria based on physical observations of different failure modes in composites - a new smeared crack approach to model failure propagation - a new pressure-dependent constitutive law. 
Type Of Material Computer model/algorithm 
Provided To Others? No  
Impact 2nd World-Wide Failure Exercise. In this exercise, world-leading experts were asked to use their theories to provide blind predictions for a comprehensive array of benchmark cases for fail- ure of composites. The theories, and their proposers, were then ranked in two lists corresponding to 'quantitative' and 'qualitative' merit. The blind predictions of the team STP led ranked the highest in both lists. See AS Kaddour and MJ Hinton, "Maturity of 3D failure criteria for fibre- reinforced composites: Comparison between theories and experiments: Part B of WWFE-II", Journal of Composite Materials 2013 47(67) 925966, DOI: 10.1177/0021998313478710). 
 
Description AIRBUS OPERATIONS LIMITED 
Organisation Airbus Group
Country France 
Sector Academic/University 
PI Contribution STP's failure models used extensively by Airbus: "We've been collaborating with Dr Pinho over a number of years on the development of models for failure of composite structures. This is a very challenging area and these models constitute a positive contribution to our capability to predict damage in large components." (Dr Morten Ostergaard, Airbus Senior Expert in Structure Modelling and Non-Linear Finite Element Analysis, Morten.Ostergaard@Airbus.com)
Collaborator Contribution Airbus provided funding, test cases and industrial context.
Impact 1. STP's failure models used extensively by Airbus: "We've been collaborating with Dr Pinho over a number of years on the development of models for failure of composite structures. This is a very challenging area and these models constitute a positive contribution to our capability to predict damage in large components." (Dr Morten Ostergaard, Airbus Senior Expert in Structure Modelling and Non-Linear Finite Element Analysis, Morten.Ostergaard@Airbus.com) 2. Several papers are the result of funding from Airbus.
Start Year 2007