CRack Arrest and Self-Healing in COMPosite Structures (CRASHCOMPS)

Lead Research Organisation: University of Bristol
Department Name: Aerospace Engineering

Abstract

Although composites are now widely utilised there has been a reticence from designers in using them in safety critical applications, principally because of their sensitivity to defects. Since relatively minor damage can significantly reduce performance, the 'no growth' approach (i.e. damage propagation from a defect constitutes failure) is now the mindset of the composites industry. This has led to excessively heavy components, shackling of innovative design, and a need for frequent inspection during service. However, the research community has made considerable steps in understanding damage modes and the development of robust failure models. A step change in composites technology could be achieved by adopting a philosophy in which some damage growth can be tolerated (i.e. be 'damage tolerant' or 'fail-safe); this would provide considerable weight and cost savings and offer designers greater freedom to formulate new designs. Furthermore, there are numerous applications in which a component is expected to tolerate significant damage growth yet still be fit for service; for example, collision damage to a transport vehicle. In such an application, severe damage is introduced whilst the structure is under significant load, and subsequently crack growth is highly likely; a no-growth criterion cannot be used, and damage propagation must be tolerated. An effective approach to achieve this is by employing CRack Arrest and Self-Healing COMPosite Structures (CRASHCOMPS). Uniquely, composites offer the freedom to 'tailor' internal architecture, hybridise and introduce novel features in order to achieve such a capability.

Publications

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McCombe G (2012) X-ray damage characterisation in self-healing fibre reinforced polymers in Composites Part A: Applied Science and Manufacturing

 
Description The use of composites in safety critical applications is restricted by their sensitivity to low-energy impact caused, for example, by hailstorms, runway debris, dropped tools and, in some cases service trucks bumping into commercial airliners during turnaround. This has led to overdesigned, heavier components being used to compensate for this susceptibility. The CRASHCOMPS project starts from the premise that damage in a composite structure should not hinder design; instead, it should be anticipated and compensated for via arrest and healing. The philosophy has been to allow damage to happen but steer it to a predetermined location and then effect remedial action once it is isolated within the composite structure.

Teams at Bristol and Imperial College London have worked together with two principal aims. Firstly, to formulate and demonstrate crack arrest/redirection concepts in damaged and undamaged polymer composite structures under tensile, compressive and flexural loading. These concepts were designed to inhibit the growth of rapid, unstable cracks, such that catastrophic failure of the structure was hindered. Secondly, such structures were made to incorporate a self-healing capability whereby the arrested crack could then be autonomously healed. When used in conjunction, these techniques have been shown to provide a unique ability to arrest and heal critical cracks. The research has focused on fibre reinforced plastics (FRP), as these have a particular susceptibility to impact damage and subsequent crack growth but the concepts are applicable to any significant damage in aerospace, marine, civil and transport structures. The research has provided a better understanding of the failure processes within FRP structures, and has produced solutions to reduce their sensitivity to service-induced damage. Material and structural configurations in FRPs have been developed to demonstrate radical solutions to redirecting and healing crack growth.
Exploitation Route Demonstration of crack arrest/manipulation using thermoplastic interleave layers at critical interfaces to constrain impact damage formation/propagation under both static and dynamic loading.
Implementation and comprehensive understanding of a vascular network within a FRP laminate and the subsequent interaction in FRPs.
Demonstration of full compression strength recovery post-impact via vascular self-healing.
Analytical modelling of healing agent infusion into damage and sensitivity of compression strength recovery to extent of repair.
Improved understanding of compressive failure in multi-directional laminates.
Positive effect of mixing different fibres (hybridisation)in the same matrix has been observed.
Constant crack speed observed during plane compression fracture. Crack speed appears proportional to strain energy at fracture.
Two concepts for potential crack redirection and arrest tested under dynamic crack growth conditions.
Development of novel PolyHIPE insert as potential healing agent carrier, found suitable for autoclave process.
Finite Element based modelling of compressive dynamic crack growth developed and validated against test data.
Development of a self-healing Z-pin concept for combined crack suppression and self-healing.
Sectors Aerospace, Defence and Marine,Construction,Manufacturing, including Industrial Biotechology

URL http://www3.imperial.ac.uk/people/e.greenhalgh/research/crackarrest
 
Description CRASHCOMPS 
Organisation Airbus Group
Department Airbus Operations
Country United Kingdom 
Sector Private 
PI Contribution The principal aims of this research are twofold. Firstly, to formulate and demonstrate crack arrest/redirection concepts in polymer composite structures under tensile, compressive and flexural loading. These concepts will be designed to inhibit the growth of rapid, unstable cracks, such that global (catastrophic) failure of the structure is hindered. Secondly, these structures will incorporate a self-healing capability whereby the arrested crack will then be autonomously healed. This is analogous to the numerous examples in nature where materials are generally damage tolerant and capable of self-repair.When used in conjunction, these two techniques will provide a unique ability to arrest and heal critical cracks. The research will focus on fibre reinforced epoxy panels, with and without structural features such as stiffeners and ply drops. The initial damage state investigated will be intra-ply fracture and inter-ply delamination and the concepts developed will be applicable to any significant damage, such as penetrative impact, in aerospace, marine, civil and transport structures. At the very least, the research will provide a better understanding of the failure processes within composite structures, and offer solutions to reduce their sensitivity to service-induced damage. It will develop material and structural configurations in composite structures incorporating design features to arrest the development of crack initiation and propagation coupled with a unique self-healing capability. At the very best, it will develop and demonstrate radical solutions to redirecting and healing crack growth in advanced composite structures.
Collaborator Contribution DSTL attended our quarterly meetings, providing excellent support and insight into MoD needs. This activity also led to further funds from MoD via Team MAST. The link with Airbus led to a modest additional feasibility study of applying SH to fuselage structures. This included Airbus personnel using facilities at Bristol which contributed to an MSc Thesis (J Altmeyer, 2010). As well as attending regular QPMs, R-R provided input to and specification for demonstrator sub-elements. BAE Systems SRC attended all QPMs and provided loan of ELS test rig facilities and input to demonstrator design and specification. Hexcel attended all QPMs and provided input to test specimen/demonstrator design and specification Dr O'Brien (NASA Langley) spent 3 months working between ICL and UoB funded by Floyd Thompson Fellowship from NASA Langley, Summer 2011/2012. This activity investigated the novel concept of self-healing Z-pins with a paper presented at ICCM19, July 2013.
Impact Presentations about the project have been delivered to the partner organisations. Further discussions are ongoing as to how to exploit the findings within these organisations.
Start Year 2009
 
Description CRASHCOMPS 
Organisation BAE Systems
Country United Kingdom 
Sector Private 
PI Contribution The principal aims of this research are twofold. Firstly, to formulate and demonstrate crack arrest/redirection concepts in polymer composite structures under tensile, compressive and flexural loading. These concepts will be designed to inhibit the growth of rapid, unstable cracks, such that global (catastrophic) failure of the structure is hindered. Secondly, these structures will incorporate a self-healing capability whereby the arrested crack will then be autonomously healed. This is analogous to the numerous examples in nature where materials are generally damage tolerant and capable of self-repair.When used in conjunction, these two techniques will provide a unique ability to arrest and heal critical cracks. The research will focus on fibre reinforced epoxy panels, with and without structural features such as stiffeners and ply drops. The initial damage state investigated will be intra-ply fracture and inter-ply delamination and the concepts developed will be applicable to any significant damage, such as penetrative impact, in aerospace, marine, civil and transport structures. At the very least, the research will provide a better understanding of the failure processes within composite structures, and offer solutions to reduce their sensitivity to service-induced damage. It will develop material and structural configurations in composite structures incorporating design features to arrest the development of crack initiation and propagation coupled with a unique self-healing capability. At the very best, it will develop and demonstrate radical solutions to redirecting and healing crack growth in advanced composite structures.
Collaborator Contribution DSTL attended our quarterly meetings, providing excellent support and insight into MoD needs. This activity also led to further funds from MoD via Team MAST. The link with Airbus led to a modest additional feasibility study of applying SH to fuselage structures. This included Airbus personnel using facilities at Bristol which contributed to an MSc Thesis (J Altmeyer, 2010). As well as attending regular QPMs, R-R provided input to and specification for demonstrator sub-elements. BAE Systems SRC attended all QPMs and provided loan of ELS test rig facilities and input to demonstrator design and specification. Hexcel attended all QPMs and provided input to test specimen/demonstrator design and specification Dr O'Brien (NASA Langley) spent 3 months working between ICL and UoB funded by Floyd Thompson Fellowship from NASA Langley, Summer 2011/2012. This activity investigated the novel concept of self-healing Z-pins with a paper presented at ICCM19, July 2013.
Impact Presentations about the project have been delivered to the partner organisations. Further discussions are ongoing as to how to exploit the findings within these organisations.
Start Year 2009
 
Description CRASHCOMPS 
Organisation Defence Science & Technology Laboratory (DSTL)
Country United Kingdom 
Sector Public 
PI Contribution The principal aims of this research are twofold. Firstly, to formulate and demonstrate crack arrest/redirection concepts in polymer composite structures under tensile, compressive and flexural loading. These concepts will be designed to inhibit the growth of rapid, unstable cracks, such that global (catastrophic) failure of the structure is hindered. Secondly, these structures will incorporate a self-healing capability whereby the arrested crack will then be autonomously healed. This is analogous to the numerous examples in nature where materials are generally damage tolerant and capable of self-repair.When used in conjunction, these two techniques will provide a unique ability to arrest and heal critical cracks. The research will focus on fibre reinforced epoxy panels, with and without structural features such as stiffeners and ply drops. The initial damage state investigated will be intra-ply fracture and inter-ply delamination and the concepts developed will be applicable to any significant damage, such as penetrative impact, in aerospace, marine, civil and transport structures. At the very least, the research will provide a better understanding of the failure processes within composite structures, and offer solutions to reduce their sensitivity to service-induced damage. It will develop material and structural configurations in composite structures incorporating design features to arrest the development of crack initiation and propagation coupled with a unique self-healing capability. At the very best, it will develop and demonstrate radical solutions to redirecting and healing crack growth in advanced composite structures.
Collaborator Contribution DSTL attended our quarterly meetings, providing excellent support and insight into MoD needs. This activity also led to further funds from MoD via Team MAST. The link with Airbus led to a modest additional feasibility study of applying SH to fuselage structures. This included Airbus personnel using facilities at Bristol which contributed to an MSc Thesis (J Altmeyer, 2010). As well as attending regular QPMs, R-R provided input to and specification for demonstrator sub-elements. BAE Systems SRC attended all QPMs and provided loan of ELS test rig facilities and input to demonstrator design and specification. Hexcel attended all QPMs and provided input to test specimen/demonstrator design and specification Dr O'Brien (NASA Langley) spent 3 months working between ICL and UoB funded by Floyd Thompson Fellowship from NASA Langley, Summer 2011/2012. This activity investigated the novel concept of self-healing Z-pins with a paper presented at ICCM19, July 2013.
Impact Presentations about the project have been delivered to the partner organisations. Further discussions are ongoing as to how to exploit the findings within these organisations.
Start Year 2009
 
Description CRASHCOMPS 
Organisation Hexcel Composites Ltd
Country United Kingdom 
Sector Private 
PI Contribution The principal aims of this research are twofold. Firstly, to formulate and demonstrate crack arrest/redirection concepts in polymer composite structures under tensile, compressive and flexural loading. These concepts will be designed to inhibit the growth of rapid, unstable cracks, such that global (catastrophic) failure of the structure is hindered. Secondly, these structures will incorporate a self-healing capability whereby the arrested crack will then be autonomously healed. This is analogous to the numerous examples in nature where materials are generally damage tolerant and capable of self-repair.When used in conjunction, these two techniques will provide a unique ability to arrest and heal critical cracks. The research will focus on fibre reinforced epoxy panels, with and without structural features such as stiffeners and ply drops. The initial damage state investigated will be intra-ply fracture and inter-ply delamination and the concepts developed will be applicable to any significant damage, such as penetrative impact, in aerospace, marine, civil and transport structures. At the very least, the research will provide a better understanding of the failure processes within composite structures, and offer solutions to reduce their sensitivity to service-induced damage. It will develop material and structural configurations in composite structures incorporating design features to arrest the development of crack initiation and propagation coupled with a unique self-healing capability. At the very best, it will develop and demonstrate radical solutions to redirecting and healing crack growth in advanced composite structures.
Collaborator Contribution DSTL attended our quarterly meetings, providing excellent support and insight into MoD needs. This activity also led to further funds from MoD via Team MAST. The link with Airbus led to a modest additional feasibility study of applying SH to fuselage structures. This included Airbus personnel using facilities at Bristol which contributed to an MSc Thesis (J Altmeyer, 2010). As well as attending regular QPMs, R-R provided input to and specification for demonstrator sub-elements. BAE Systems SRC attended all QPMs and provided loan of ELS test rig facilities and input to demonstrator design and specification. Hexcel attended all QPMs and provided input to test specimen/demonstrator design and specification Dr O'Brien (NASA Langley) spent 3 months working between ICL and UoB funded by Floyd Thompson Fellowship from NASA Langley, Summer 2011/2012. This activity investigated the novel concept of self-healing Z-pins with a paper presented at ICCM19, July 2013.
Impact Presentations about the project have been delivered to the partner organisations. Further discussions are ongoing as to how to exploit the findings within these organisations.
Start Year 2009
 
Description CRASHCOMPS 
Organisation National Aeronautics and Space Administration (NASA)
Department NASA Langley Research Centre
Country United States 
Sector Public 
PI Contribution The principal aims of this research are twofold. Firstly, to formulate and demonstrate crack arrest/redirection concepts in polymer composite structures under tensile, compressive and flexural loading. These concepts will be designed to inhibit the growth of rapid, unstable cracks, such that global (catastrophic) failure of the structure is hindered. Secondly, these structures will incorporate a self-healing capability whereby the arrested crack will then be autonomously healed. This is analogous to the numerous examples in nature where materials are generally damage tolerant and capable of self-repair.When used in conjunction, these two techniques will provide a unique ability to arrest and heal critical cracks. The research will focus on fibre reinforced epoxy panels, with and without structural features such as stiffeners and ply drops. The initial damage state investigated will be intra-ply fracture and inter-ply delamination and the concepts developed will be applicable to any significant damage, such as penetrative impact, in aerospace, marine, civil and transport structures. At the very least, the research will provide a better understanding of the failure processes within composite structures, and offer solutions to reduce their sensitivity to service-induced damage. It will develop material and structural configurations in composite structures incorporating design features to arrest the development of crack initiation and propagation coupled with a unique self-healing capability. At the very best, it will develop and demonstrate radical solutions to redirecting and healing crack growth in advanced composite structures.
Collaborator Contribution DSTL attended our quarterly meetings, providing excellent support and insight into MoD needs. This activity also led to further funds from MoD via Team MAST. The link with Airbus led to a modest additional feasibility study of applying SH to fuselage structures. This included Airbus personnel using facilities at Bristol which contributed to an MSc Thesis (J Altmeyer, 2010). As well as attending regular QPMs, R-R provided input to and specification for demonstrator sub-elements. BAE Systems SRC attended all QPMs and provided loan of ELS test rig facilities and input to demonstrator design and specification. Hexcel attended all QPMs and provided input to test specimen/demonstrator design and specification Dr O'Brien (NASA Langley) spent 3 months working between ICL and UoB funded by Floyd Thompson Fellowship from NASA Langley, Summer 2011/2012. This activity investigated the novel concept of self-healing Z-pins with a paper presented at ICCM19, July 2013.
Impact Presentations about the project have been delivered to the partner organisations. Further discussions are ongoing as to how to exploit the findings within these organisations.
Start Year 2009
 
Description CRASHCOMPS 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
PI Contribution The principal aims of this research are twofold. Firstly, to formulate and demonstrate crack arrest/redirection concepts in polymer composite structures under tensile, compressive and flexural loading. These concepts will be designed to inhibit the growth of rapid, unstable cracks, such that global (catastrophic) failure of the structure is hindered. Secondly, these structures will incorporate a self-healing capability whereby the arrested crack will then be autonomously healed. This is analogous to the numerous examples in nature where materials are generally damage tolerant and capable of self-repair.When used in conjunction, these two techniques will provide a unique ability to arrest and heal critical cracks. The research will focus on fibre reinforced epoxy panels, with and without structural features such as stiffeners and ply drops. The initial damage state investigated will be intra-ply fracture and inter-ply delamination and the concepts developed will be applicable to any significant damage, such as penetrative impact, in aerospace, marine, civil and transport structures. At the very least, the research will provide a better understanding of the failure processes within composite structures, and offer solutions to reduce their sensitivity to service-induced damage. It will develop material and structural configurations in composite structures incorporating design features to arrest the development of crack initiation and propagation coupled with a unique self-healing capability. At the very best, it will develop and demonstrate radical solutions to redirecting and healing crack growth in advanced composite structures.
Collaborator Contribution DSTL attended our quarterly meetings, providing excellent support and insight into MoD needs. This activity also led to further funds from MoD via Team MAST. The link with Airbus led to a modest additional feasibility study of applying SH to fuselage structures. This included Airbus personnel using facilities at Bristol which contributed to an MSc Thesis (J Altmeyer, 2010). As well as attending regular QPMs, R-R provided input to and specification for demonstrator sub-elements. BAE Systems SRC attended all QPMs and provided loan of ELS test rig facilities and input to demonstrator design and specification. Hexcel attended all QPMs and provided input to test specimen/demonstrator design and specification Dr O'Brien (NASA Langley) spent 3 months working between ICL and UoB funded by Floyd Thompson Fellowship from NASA Langley, Summer 2011/2012. This activity investigated the novel concept of self-healing Z-pins with a paper presented at ICCM19, July 2013.
Impact Presentations about the project have been delivered to the partner organisations. Further discussions are ongoing as to how to exploit the findings within these organisations.
Start Year 2009