Composites for Hydrogen Storage for Green Aviation

by Valeska Ting; James Griffith; Charlie Brewster; Lui Terry  


Of all of the modes of transportation that we need to decarbonize, air travel is perhaps the most challenging. In contrast to road or marine transport, which can realistically be delivered with battery or hybrid technologies, the sheer weight of even the best available batteries makes long-haul air travel (such as is needed to maintain our current levels of international mobility) prohibitive. Hydrogen is an extremely light, yet supremely energy-dense energy vector. It contains three times more energy per kilogram than jet fuel, which is why hydrogen is traditionally used as rocket fuel.   

Companies like Airbus are currently developing commercial zero-emission aircraft powered by hydrogen. A key challenge for the use of hydrogen is that it is a gas at room temperature, requiring use of very low temperatures and specialist infrastructure to allow its storage in a more convenient liquid form. To deliver this disruptive technology Airbus are undertaking a radical redesign of their future fleet to enable the use of liquid hydrogen fuel tanks[5].

A jet flying in the sky

In its liquid form, hydrogen needs to be stored at –253oC. At these temperatures, traditional polymer matrices are susceptible to microcracking due to the build-up of thermally induced residual stresses. Research at the Bristol Composites Institute at the University of Bristol is looking at how we can develop new materials to produce tough, microcrack resistant matrices for lightweight composite liquid hydrogen storage tanks. 

We are also looking at the use of smart composites involving nanoporous materials – materials that behave like molecular sponges to spontaneously adsorb and store hydrogen at high densities– for onboard hydrogen storage for future aircraft designs. Hydrogen adheres to the surface of these materials; more surface area equals more hydrogen. One gram of our materials has more surface area than 5 tennis courts, with microscopic pores less than 1 billionth of a meter in diameter. These properties allow us to store hydrogen at densities hundreds of times greater than bulk hydrogen under the same conditions. Whilst simultaneously improving the conditions currently needed for onboard hydrogen storage. Our research looks to improve this by tailoring the composition of these materials to store even greater quantities of hydrogen beyond the densities dictated by surface area.  

With hydrogen quickly becoming recognised around the world as the aviation fuel of the future, France and Germany are investing billions in ambitious plans for hydrogen-powered passenger aircraft. To keep pace with the development of new aircraft by industry, there is a parallel need for rapid investment into refuelling infrastructure at international airports to allow storage and delivery of the liquid hydrogen fuel. Urgent investment to also upgrade the hydrogen supply chain is imperative. The UK Government’s announcement of new investment in wind turbines and offshore renewables will certainly boost the UK’s ability to generate sustainable hydrogen fuel and presents additional opportunities for new industries and markets.  

It seems industry is finally ready to take the leap away from its reliance on fossil fuel to more sustainable technologies. Decisive action and public investment into upgrading our hydrogen infrastructure will allow us to realise the many benefits of this and will make sure the UK remains competitive in this low-carbon future.



Images and permissions available from:  


[1] Hydrogen-powered aviation – A fact-based study of hydrogen technology, economics, and climate impact by 2050
[2] Liquid Hydrogen–the Fuel of Choice for Space Exploration 
[3] Airbus looks to the future with hydrogen planes 
[4] Liquid Hydrogen Delivery 
[5] Airbus reveals new zero-emission concept aircraft 
[6] Bristol Composites Institute 
[7] Nanocage aims to trap and release hydrogen on demand 
[8] Engineering porous materials 
[9] France bets on green plane in package to ‘save’ aerospace sector 
[10] Germany plans to promote ‘green’ hydrogen with €7 billion 
[11] EU Hydrogen Roadmap 
[12] Boris Johnson: Wind farms could power every home by 2030  

Bristol Composites Institute at ECCM20

We are pleased to announce an impressive line up of academics, researchers and PhD students from the Bristol Composites Institute (BCI) who will be presenting their latest work at ECCM 20 (the 20th European Conference on Composite Materials) in Lausanne, Switzerland from 26th to 30th June 2022.

This year’s conference is on the theme of “Composites meet Sustainability” and we will highlight our commitment toward sustainability across a range of activities spanning academic research, industrial collaborations and education programmes.

Our Industrial Doctorate Centre (IDC) in Composites Manufacture is also hosting a special session! The IDC aims to provide the UK composites manufacturing industry with Research Engineers equipped with the necessary advanced technical and leadership skills required for effective adoption of new knowledge and technologies in composites manufacture. For more details and informal discussion please contact Professor Janice Barton ( at booth #6 during the conference. Details of speakers at the session can be found here.


Monday 27 June BCI speaker line-up:

Garden 1 / 11:30 – speaker: Nguyen DUC (62031). Title: Real-time Material Measurement for Automated Fibre Placement.

Garden 4 / 11:30 – speaker: Mudan CHEN (61809). Title: Experimental study on the mechanical
behaviour of carbon-fibre Z-pin reinforced curved composite laminates under four-point bending.

Garden 3 / 12:45 – speaker: Ganapathi AMMASAI SENGODAN (61675). Title: Hygro-thermal effects on the translaminar fracture toughness of composite laminates.

Garden 8 / 15:30 – speaker: Athina Kontopoulou (61936). Title: Shape and Size Optimization of Additive Manufactured Lattice Cores with an Evolutionary-Based Approach for High Performance Sandwich Panels.

Garden 4 / 17:00 – speaker Chantal LEWIS (61681). Title: An investigation into the performance is ADFRC produced with HiPerDiF 3G.

Garden 4 / 17:15 – speaker: Gustavo QUINO (61865). Title: Design of a bending experiment for mechanical characterisation of pultruded rods under compression.

Garden 6 / 17:15 – speaker: Roy BULLOCK (61961). Title: Ply Orientation Effects in Multidirectional Carbon/ Epoxy Open-Hole Specimens Subjected to Shear Loading.

Garden 7 / 18:30 – speaker: Xiaoyang SUN (61857). Title: An Experimental Study of Crack Propagation in Stiffened Over-height Compact Tension (SOCT) Specimens.

Garden 6 / 18:45 – speaker: Neha CHANDARANA (62343). Title: Damage characterisation in open-hole composites using acoustic emission and finite element, validated by X-ray CT.


Tuesday 28 June BCI speaker line-up:
Garden 10 / 10:30 – speaker: Pedro GALVEZ-HERNANDEZ (61642). Title:  Uncured out-of-autoclave composite prepregs characterizations via deep learning.

Garden 8 / 11:45 – speaker: Tobias LAUX (62344). Title: Hybrid testing for composite substructures.

Keynote Lecture 4 / 14:00 – speaker: Prof. Ivana Partridge. Title: Toughening approaches in composites – a perspective.

Garden 5 / 14:30 – speaker: Aewis HII (62521). Title: Development of a Concurrent Multi-scale Analysis Framework using Shell Elements for the Progressive Failure Analysis of Composites.

Garden 9 / 14:30 – speaker: Joseph SOLTAN (62424). Title: Modular Infusion: Novel Approaches to Segregation and Control of Flow Fronts Within Liquid Resin Moulding.

Garden 9 / 14:45 – speaker: Laura Rhian PICKARD (62302).Title: Manufacturing Advances for Pultruded Rod Based Structural Members and Thick Ply Systems.

Garden 7 / 17:30 – speaker: Antonio MELRO (62388). Title: Modelling delamination resistance of
composite laminates reinforced with novel z-pins through an energy-equivalent bridging map

Garden 1 / 18:00 –  speaker: Axel WOWOGO (61636). Title: Influence of Automated Fibre Placement processing parameters on the consolidation of out-of-autoclave prepreg.

Garden 9 / 18:15 – speaker: Janice BARTON (62222). Title: A new test for validating models of lightning strike damage on CFRP laminates.

Garden 10 / 18:15 – speaker: Narongkorn KRAJANGSAWASDI (61680). Title: Highly Aligned Discontinuous Fibre Composite Filaments for Fused Deposition Modelling: Comparison between printed and lay-up open-hole sample.


Wednesday 29 June BCI line-up:

Garden 4 / 10:15 – speaker: Ali KANDEMIR (61786). Title: Interfacial shear strength of flax fibre with sustainable matrices.

Garden 4 / 10:30 – speaker: Stephen Hallett (61654). Title: :Novel Z-pin Technologies for Through Thickness Reinforcements.

Garden 5 / 10:30 – speaker Xun WU (61812). Title: Improved Energy Absorption of Novel Hybrid Configurations Under Static Indentation

Garden 7 / 11:45 – speaker: Ram KARTHIK RAMAKRISHNAN (66298). Title: Combined DIC-Infrared thermography for high strain rate testing of composites.

Garden 7 / 14:30 – speaker: Eduardo SANTANA DE VEGA (62438). Title: Improving the mode II delamination bridging performance of fibrous composite Z-pins.

Garden 4 / 17:00 – Ogun YAVUZ BURAK (62348). Title: Tensile characterisation of HiPerDiF PLA/Carbon fibre tape under processing conditions.

Garden 5 / 18:00 – speaker: Anatoly Koptelov (61710). Title: A novel closed-loop testing framework for decoding consolidation deformation mechanisms in manufacturing.

Poster session – David LANGSTON (62605). Title: Torsional Testing of Wind Turbine Blades.


Thursday 30 June BCI speaker line-up:

Garden 7 / 08:30 – speaker: Katherine NELMS (62050). Title: Effect of fiber microstructure on kinking in unidirectional fiber reinforced composites imaged in real time under axial compression.

Garden 8 / 08:45 – speaker: Ole THOMSEN (62400). Title: Validation of Composite Aerostructures through Integrated Multi-Scale Modelling and High-Fidelity Substructure Testing Facilitated by Design of Experiments and Bayesian learning.

Campus A / 09:00 – speaker: Rafael Ruiz Iglesias (62267). Title: Surface and subsurface damage assessment of multi[1]directional composite laminates utilizing a full field imaging technique.

Campus A / 09:45 – speaker: Geir Olafsson (61847). Title: Assessment of complex structural scale composite structures by adapting thermoelastic stress analysis for 3D perspective imaging.


Don’t miss the latest news and updates from the ECCM Conference via the Bristol Composites Institute Twitter account: ‎@UoBrisComposite!


Working with Airbus in Composite Manufacturing R&T

We interviewed Bristol Composites Institute PhD student Michael O’Leary about his PhD project and the mutual benefits of working with Airbus on a cutting-edge research project.

How did you end up studying at the Bristol Composites Institute?

man looking at the camera smiling
Michael O’Leary

On leaving school, I realised I wanted to pursue a degree in Engineering, eventually specialising in Aeronautical Engineering and graduating with my bachelors from the University of Limerick. I had my final year project examined by Professor Paul Weaver, who recommended applying to the Bristol Composites Institute for PhD.

I decided that the Centre for Doctoral Training would be a great fit for me as I had enjoyed the research aspect of my final year. The collaborative environment of the CDT, being surrounded by people with similar research interests and skills, was a great selling point for me.

What are you working on?

My project is focused on integrated structures with semi-cured elements.

For future wing structure, we are moving towards more highly integrated and larger structures. As we make these integrated structures, we start to encounter some of the manufacturing challenges associated with the scale, such as element alignment and complexity.

The objective of my project is to break the integrated structure back down into smaller pieces and use them semi-cured as a building block to bring them back together. For instance, the state of the art for current structures manufacturing is using a skin, bonded stringers, and bolted ribs. Why not semi-cure each individual part and integrate them all together for a final cure?

How do you manufacture integrated structures with semi-cured elements?

The manufacturing process is a two-step curing process. The initial step is to create the semi-cured elements with a pre-designated degree of curing, somewhere between uncured and fully cured, hence the name. After the curing process, the semi-cured element can be stored, trimmed, and inspected. If they are of acceptable quality, they can then be integrated.

What are some of the manufacturing challenges when using semi-cured elements?

The main manufacturing challenges that we are facing are about determining the degree of curing and scaling, especially for more complex geometries as there are tooling requirements that can complicate the process.

Regardless of specimen manufacturing method fibre bridging was witnessed during DCB testing
Double Cantilever Beam tests were carried out on initially semi-cured and normal, single step, fully cured laminates, with both sample sets displaying similar failure patterns, and failure loads.

What are the next steps for this work?

The next steps are to continue to determine the optimal degree of cure for semi-curing along with better understanding how semi-cured interfaces are forming. Outside of this, we will continue to prove the feasibility of semi-curing by starting to produce parts at a scale greater than coupon level.

How will the project results benefit the academic and industrial project partners?

Proving the feasibility of this work will provide the industry with an additional manufacturing tool that they can use when designing future structures. Hopefully, my work will lead to further questions which can be posed to incoming PhD candidates.

How has your cooperation with industrial partners supported the development of this project or your skills?

My primary industrial partner is Airbus. The industrial supervisors have been very helpful and supportive providing important technical knowledge and ideas which have made their way into my work. Having an industrial project gives a different perspective, it really helps me to see how my work can be applied in the real world.

Through this industrial project, I had the opportunity to interact with one of the world’s largest aerospace manufacturers. It has helped foster relationships which would not have been possible outside of this project.

CerTest – Certification for Design: Reshaping the Testing Pyramid

One of the larger activities currently happening at the Bristol Composites Institute is CerTest. This EPSRC (UK Engineering and Physical Sciences Research Council) Programme Grant, with £6.9million of funding, started in July 2019 and will run for 5 years.

CerTest is led by Bristol Composites Institute Co-director, Professor Ole Thomsen at the University of Bristol, with academic collaboration partners at the University of Bath, University of Exeter, and University of Southampton.

The aim of the research in this multidisciplinary project is to develop new approaches to enable lighter, more cost and fuel-efficient composite aero-structures. This vision will be realised through four flexible but highly interlinked research challenges:

  1. Multi Scale Performance Modelling
  2. Features and Damage Characterisation
  3. Data-rich High Fidelity Structural Characterisation
  4. Integration and Methodology Validation

The four research challenges will result in a new approach for integrated high-fidelity structural testing and multi-scale statistical modelling through Design of Experiments (DoE) and Bayesian Learning.

The efficient exploitation and optimisation of advanced composite aero-structures is fundamentally prohibited by current test, simulation and certification approaches, and CerTest seeks to break this impasse by holistically addressing the challenges that are preventing step-changes in future engineering design by reshaping the ‘Testing Pyramid’.

The CerTest project is supported by seven key industry partners who provide important steer and valuable market insight along with several funded studentships. Airbus, Rolls Royce, BAE Systems, GKN Aerospace, NCC, the Alan Turing Institute, and CFMS meet with the CerTest team at least twice a year and are keen to see the research succeed.

The project is further supported by an Independent Advisory Board of experts from international and UK based academia, industry and regulators that provide further guidance and support to ensuring CerTest reaches its full potential and realises its goals and objectives.

This is one of the largest collaborations the Bristol Composites Institute has ever undertaken, and a lot of groundwork has gone into supporting the collaboration, flow and sharing of data between the partners. The current CerTest team has 37 members and counting.

group of co-workers standing in front of a building
The CerTest team at an internal meeting held at the National Composites Centre.

Further information

For more information and updates, visit the CerTest website.

SABRE – Novel blade technologies greatly improve helicopter efficiency

We interviewed the lead investigator of the SABRE projectDr. Benjamin Woods.

What is the SABRE project?

SABRE stands for ‘Shape Adaptive Blades for Rotorcraft Efficiency’. The four-year, €6 million, EU-funded project brings together a consortium of six research institutions from across Europe to develop ground-breaking new helicopter blade designs capable of changing shape in real-time to reduce noise, fuel burn and CO2 emissions.

Can you tell us what motivated this work?

In a word, sustainability. Reducing emissions from current flying technology is imperative if we want a credible chance to tackle climate change, hence developing new technologies that are more efficient and drastically reduce fuel burn is key to becoming more sustainable. 

How are you proposing to achieve better flying efficiency for helicopters?

yellow helicopter on the ground

Current designs for helicopter blades are rife with inefficiency.  The problem with helicopters is that blades will experience cyclic changes in airflow as they rotate. These differences in airflow velocity are detrimental to the performance of the rotor. This is a well-known issue and current rotor designs can change the overall pitch (orientation) of each blade as it spins around the helicopter to partially mitigate this issue. Unfortunately, the pitching solution is not ideal as it pitches the whole blade.  

Instead, we are proposing to develop different morphing concepts that will enable us to quickly and accurately control the shape of each blade and hence the airflow, during each rotation.  

What are these morphing concepts?

There are many key design parameters that should be considered when creating rotor blades. For example, you should ask ‘how much curvature is there in the aerofoil?’, ‘how does the length of the aerofoils vary over the blade?’, ‘how much twist is there in the blade?’. These are the types of features that engineers play with to optimise rotorcraft performance, with compromises being required due to the wide range of operating conditions. Those are the things that we would love to be able to change – but in real-time – to allow us to fully respond to the different operating conditions without the need to compromise. We are looking at exactly those factors. 

Six promising morphing blade concepts are being investigated. Two concepts can actively change the blade twist. Another two can actively change the aerofoil curvature (camber). One concept can increase the length of the aerofoil, and the last concept can alter the blade dynamic response.

Active camber, active chord, active tendons. active twist, and negative stiffness passive energy balancing.
Morphing concepts investigated by SABRE

What have you found out so far?

Using one concept at a time resulted in a fuel burn reduction of up to 5%, but when we looked at multiple concepts in different parts of each blade to attack different elements of physics, that’s when we saw significant reductions of up to 11%. There is certainly scope for further reductions, and with the right combination of technologies, fuel burn could be reduced by as much as 20%. 

What are your next steps?

It will be a while before this technology becomes mainstream. Development times of up to 30 years are “completely standard” for novel technologies in civil aerospace because the safety requirements are so rigorous. However, SABRE’s research could have applications elsewhere – more specifically, with renewable wind energy. This will likely be part of my next investigation.

Find out more

For more information, visit the SABRE Project website.