Category: Manufacturing and Design

Real-time Quality Control in Automated Fibre Placement using Artificial Intelligence 

Posted on by jo.rich

by Gabriel Burke, Duc H. Nguyen, Iryna Tretiak.

The growing demand for ever more cost and labour effective production of large, lightweight, and geometrically complex composite structures has led to the replacement of traditional manufacturing processes, such as hand lay-up and vacuum bagging, with automated processes such and Automated Fibre Placement (AFP). The AFP method uses robotic arms to deposit layers of carbon fibre reinforced composites (CFRP) onto bespoke moulds. This process can create complex shapes at high speed. However, manufacturing-induced defects are inevitable during AFP. This degrades the strength of the final parts and creates a major waste problem, with defective parts discarded in some cases. While automation of composite manufacturing processes has been successfully industrialised, inspection is still largely a manual process.

As we move towards Industry 4.0, it is possible to optimise inspection during the AFP manufacturing process. One option of improving inspection is to implement artificial intelligence.

Our research team at the Bristol Composites Institute (BCI) has successfully designed and implemented a system that performs real-time defect detection and classification during the AFP process, providing information on the location and type of defects in the tape almost instantly after it has occurred.

The developed system is built upon a convolutional neural network (CNN), which uses deep learning techniques to detect defects based on input data images. These images were generated using data collected from a Micro-Epsilon profilometry sensor attached to the AFP gantry. This system can correctly identify and differentiate between three defects (fold, twist, and pucker) and does so in real-time using a three-stage algorithm:

1. Live data collection and pre-processing;

2. A sampling and image optimisation algorithm to produce a moving window of input images for the CNN;

3. Defect detection/classification using the CNN.

Due to this modular design, it is possible to modify each stage to fit the needs of other AFP applications. For example, the CNN can be retrained to ‘look’ for other defects, or the sampler could be modified to collect images at a different frequency based on the scale of the part being manufactured.

This novel inspection technique provides great potential to improve efficiency and reduce waste in composites manufacturing.

 

Following the success of the initial proof-of-concept phase, the team is looking to upscale the current prototype to meet the speed and robustness requirements of operational systems in industry. 

Process Simulation For Reduced-defect Composites

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by Siyuan Chen, Stephen Hallett and Jonathan Belnoue.

 

As the demand for carbon fibre-reinforced composites structures is rapidly growing, the industrial community continues to seek new manufacturing technologies that are low-defect, low-cost, highly efficient and environmental-friendly. Liquid molding is regarded as a cheaper alternative to the traditional prepreg/autoclave approach, however, the latter is often the favoured manufacturing route in the aerospace sector (where safety is paramount) as it allows for the production of better quality parts. One of the many challenges with infusion is the high deformability of the dry fibrous precursor materials that exposes the final structure to risks of defects and part to part variability. If the material and process (including their variabilities) are not controlled to a sufficient level, meeting design tolerances can prove challenging. These risks are traditionally mitigated through “over design” but this reduces a lot of the lightweighting advantages of using composites. 

At BCI, we explore the possibility of achieving reduced-defect forming processes in 3 different ways. Firstly, design tools accounting for manufacturing constraint that are faster than current methods available commercially are being developed [1, 2]. These tools can be used to run moderate numbers (i.e., up to a 100) of simulations and allow to explore the impact of different combination of process control parameters on final part quality. This provide the possibility of optimising the forming process. The robustness of the optimisation is then improved by building Gaussian process (GP) emulator using the dataset produced using our fast simulation tools [3]. These GP emulators can achieve a good accuracy (error < 10%) and model the impact of several input parameters by running only tens of simulations. By introducing dimension reduction and active learning algorithms, the emulators can be expended to much more complex processes with over 10 input parameters [4]. After being trained, the emulators can also provide immediate predictions for final part quality. This open the door for digital twinning where in-process sensing and real-time simulation are combined. Thus, although forming processes can be optimised using deterministic FE simulations, real-world cases are affected by lots of factors such as material and process variability. Some of these variabilities are difficult to avoid but can be measured. Quantifying them (e.g., fibre direction misalignment, tow waviness, etc), a feedback loop whereby real-time simulations are informed by live data of the process and used to adapt the manufacturing condition to improve the final part quality can be set. A forming test cell instrumented with a stereo imaging system is currently being built in our labs. This will be used to construct a prototype digital twin for forming process. 

To summarise, in our vision right first-time design and manufacture of composites can be achieved through a combination of (physics-based) digital design accounting for manufacturing constraints, fast process optimisation using data generated from process models and self-adapting manufacturing hardware controlled through emulators build from process models. 

 

 

[1] Composites: Made Faster – Rapid, physics-based simulation tools for composite manufacture (ukri.org) 

[2] JPH Belnoue, SR Hallett A rapid multi-scale design tool for the prediction of wrinkle defect formation in composite components, Materials & Design, 2020. 

[3] S. Chen, A.J. Thompson, T.J. Dodwell, S.R. Hallett, J.P.-H. Belnoue, Fast optimisation of the formability of dry fabric preforms: A Bayesian approach, Materials & Design, 230:111986, 2023. 

[4] S. Chen, A.J. Thompson, T. J. Dodwell, S.R. Hallett, J. P.-H. Belnoue. A Bayesian surrogate framework for the optimisation of high-dimensional composites forming process. In 5th International Conference on Uncertainty Quantification in Computational Science and Engineering, 2023. 

Moving cheese: energetically efficient shape shifting via embedded actuation

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Compliant materials and slender structures are susceptible to a variety of different instabilities under external stimulus or loading. Traditionally, these instabilities are avoided and classified as failure modes. In recent years, researchers at the BCI have instead attempted to use complex nonlinear behaviour for novel functionality. Simply put, if nonlinearities are understood, then they can be exploited to create well-behaved nonlinear structures. In a recent publication in Physical Review B [1], we employed ‘active modal nudging’ as a novel actuation mechanism for soft robots. In essence, we programmed a soft metamaterial to shape-shift in a rapid and energetically efficient manner by employing embedded actuation to switch between different stable post-buckled modes. 

Our work focused on a latticed metamaterial consisting of an elastomeric matrix with a 3 by 3 square array of circular holes, as shown in Figure 1. We discovered that this metamaterial has three stable post-buckling modes under pure compression, i.e. two sheared modes (sheared left and sheared right) and one symmetric polarised mode. The metamaterial was programmed to favour one of the sheared modes under axial compression via modal nudging [2]. An actuator was then embedded within the central hole to trigger a mode switch between the favoured sheared mode and the polarised mode. We demonstrated that this combination of active and passive nudging is more energetically efficient and requires smaller actuation force than the more widely used global actuation method, as shown in Figure 1(a). By toggling the metamaterial between the sheared and polarised state, we were able to make the metamaterial crawl. The effective locomotion could be employed in soft robotics systems (Figure 2). 

While in this study, we consider a specific type of soft metamaterial and a specific application, the design paradigm introduced can be extended to other scenarios where energetically efficient shape shifting may be beneficial, such as lightweight adaptive wing structures or adaptive façade and ventilation systems for net-zero buildings. 

Figure 1 The actuation force–displacement curve of the lattice metamaterial to achieve a us/L = 0.20 shear displacement amplitude, using: (a) increasing compression from the pre-buckling state; and (b) active nudging from the symmetric deformation mode. 

 

 

Figure 2 (a) A typical actuation cycle for the robot. Yellow and red lines are the reference line indicating the initial and final positions of the right and left edges. The yellow arrows represent the motion of the fixture within the step. (b) The location of the crawling robot in the initial state, after four and eight iterations. A movie of the movement of the demo robot can be found in https://journals.aps.org/prb/supplemental/10.1103/PhysRevB.107.214103/DemoCrawlingRobot.mp4 

 

 

References: 

[1] Shen, J., Garrad, M., Zhang, Q., Leao, O., Pirrera, A., & R. M. J. (2023). Active reconfiguration of multistable metamaterials for linear locomotion. Physical Review B, 107(21), 214103. 

[2] Cox, B. S., Groh, R. M. J., Avitabile, D., & Pirrera, A. (2018). Modal nudging in nonlinear elasticity: tailoring the elastic post-buckling behaviour of engineering structures. Journal of the Mechanics and Physics of Solids, 116, 135-149. 

BCI’s contribution to NCC’s Technology Pull-Through (TPT) programme, 2023-24

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The Bristol Composites Institute (BCI) was involved in both of the projects funded by the NCC in their 2023/24 Technology Pull-Through (TPT) programme, directly aligned with the NCC’s composites strategy. The TPT programme stimulates the transition of suitably mature technologies to industry and is aimed at technologies and methods that are ready to advance from a laboratory environment, typically at Technology Readiness Level (TRL) 3 to 4. One is based on Healable Interfaces, to demonstrate the viability of vitrimer composites for use in repair and end-of-life disassembly, whilst the other is focussed on the standardisation of cryogenic H2 permeability testing in composites, through the development of a test rig to provide testing guidance and data on variance in measurements in this type of testing of composite materials. The Healable Interface work is being conducted by Joe Soltan, working with NCC colleagues, Janice Barton, Dmitry Ivanov and James Kratz, and the Cryogenic Permeability Testing is being conducted by Lui Terry, with NCC colleagues and Valeska Ting. 

Healable Interfaces 

The major challenge in composite repair is that it is costly, a specialist activity, limited by geometry and largely requires cutting of reinforcing fibres, resulting in structural discontinuities. Additionally, in-field repair is typically only possible on a small number of small damage events, and current composite solutions do not offer a viable circular economy approach. The project aims to demonstrate the viability of vitrimer composites for use in repair and end-of-life disassembly. The potential benefits are: 

  • to enable in-field repair, and therefore the extension of service life and the sustainability of composite solutions 
  • to offer the possibility of disassembly through a simple breakdown method at end-of-life, enabling a better circular future for composites 
  • to de-risk composite processing through modular infusion methods 

The project focus is on skin and stiffener interfaces within wind turbine blade structures, although this technology would be relevant to a whole host of other composite applications. Work to date has included a down-selection candidate vitrimer systems, laboratory trials encompassing processability, thermal characterisation and initial mechanical testing to identify an ideal healable interface vitrimer. Future work will develop recommended manufacturing processes and cycles for healable interfaces, and prove the technology for skin/stiffener wind turbine blade structures. Sustainability impacts will provide the projected trade-off point between additional embodied energy and service life extension. At completion, it is envisaged that the application of emerging vitrimer materials in a circular composites industry will have been demonstrated. For further information, please contact Joe Soltan (joe.soltan@bristol.ac.uk) 

Cryogenic Permeability Testing 

The decarbonisation of the aviation industry is contingent on composite materials for cryogenic LH₂ storage. A key issue holding back the technology is that hydrogen permeability through composite materials at cryogenic temperatures is relatively unknown as a result of the scarcity of testing facilities able to reach the cryogenic temperatures (20 K) and a high degree of variability between existing datasets. The barrier is therefore due to a gap in the measurement infrastructure, and a lack of validated measurement standards or guidance on testing cryogenic H₂ permeability in composite materials. This project aims to develop a cryogenic H2 permeability test rig and to provide guidance for cryogenic H₂ permeability testing of composite materials, to help quantify the variance in measurement data that can be expected. The anticipated benefits are: 

  • a reliable and validated cryogenic H₂ permeability method for composite materials 
  • an experimental rig that can be extended in the future to examine interface design between composite and metallic materials 

To date, a cryogenic hydrogen permeation rig (CHyPr) has been designed and built at BCI. The first generation of CHyPr will measure permeability in any solid material between 0 to 80 bar, and from 77 to 293 K. The design and materials selection process for CHyPr however, has accounted for the expansion of the rig to encompass 20-475 K and 0-200 bar in future generations. A reusable permeation cell has been designed and manufactured, capable of measuring both through and lateral permeation of cryogenic hydrogen and now has passed the relevant pressurised equipment safety certification for use. Currently, CHyPr is undergoing calibration and validation of its seals before initial sample testing can begin. This project also involves two other partners, the National Physical Laboratory (NPL) and the University of Southampton, to complete a round-robin benchmarking study of cryogenic hydrogen permeation testing. This aims to determine the current data variance levels between test houses and to isolate the determinant factors in methodology that cause that variance. It is intended to develop guidance in this nascent field on how to better control these variables to ultimately contribute towards a standardised method for cryogenic permeability testing in composite materials. For further information on CHyPr, please contact Dr Lui Terry (lt7006@bristol.ac.uk)

Unique Modelling Capability for Composite Manufacturing

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The National Composite Centre (NCC) held an event focused on ‘Demystifying Digital Engineering’ on 23 March. This was an opportunity for guests to view and interact with a range of digital technology and skills demonstrators that accelerate engineering transformation, identifying efficiencies in product, process and technology development. This will inspire the next generation of engineers to engage with tools developed in the DETI (Digital Engineering Technology & Innovation) R&D initiative.

The Bristol Composites Institute (BCI) demonstrated a simulation tool that provides uniquely fast, and accurate simulations for the manufacturing of composite components. The automated simulation tools developed are available for industry use from BCI and the NCC, which results in significant cost savings per part by reducing the need for physical trials, which could in turn eliminate one or more design cycles. The University of Bristol also contributed to DETI with 5G work on Enabling Quantum-secure 5G enabled Mobile Edge Computing (MEC) for manufacturing, through the Smart Internet Lab, and the challenge of Enabling the Digital Thread in small engineering projects in work between CFMS and the University’s Engineering Systems and Design Institute.

People looking at the BCI stand at the event  People sat watching a presentation in a conference room

The Composites Perspectives Series

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Last year the Bristol Composites Institute launched “Composites Perspectives”, a series of talks each focusing on different topics and including two composite-expert speakers. Since June 2022, the BCI has hosted three Composite Perspectives events, with the next one arranged for 11 July 2023 (details on how to register will be released soon).

The first Composites Perspectives event took place on 14 June 2022 and saw Professor Richard Oldfield (Chief Executive, UK National Composites Centre and Honorary Industrial Professor, University of Bristol) and Professor Pascal Hubert (Werner Graupe Chair on Sustainable Composites Manufacturing and Director at the Research Center for High Performance Polymer and Composite Systems, McGill University, Canada) discuss “Composites Role in Delivering Net Zero” and “Solutions for Zero Waste Composite Prepreg Processing”, respectively.

These talks became part of a wider ‘Sustainable Composites’ programme, and in September 2022 guest speaker Dr. Tia Benson-Tolle (Director, Advanced Materials and Sustainability, Boeing Commercial Aircraft) covered the importance of “Circularity and Recycling” within sustainable composites, and Professor Ian Hamerton (NCC Professor of Polymers and Sustainable Composites, University of Bristol) discussed the “High Performance Discontinuous Fibre technology (HiPerDiF)”.

The most recent event, which took place on 14 March 2023,  focused on Transformation in Engineering, with talks from Professor Mike Hinton, Consultant in Research and Technology Partnerships, High Value Manufacturing Catapult (“Engineering Transformation”) and Professor Ole Thomsen, Co-Director of Bristol Composites Institute and NCC Chair in Composites Design and Manufacture (“Towards virtual validation of composites structures – rethinking the testing pyramid approach”).

You can read about the previous events here and recordings of each session are available to view on the BCI Youtube Channel.

We look forward to inviting you to our future Composites Perspectives events.

BCI / NCC Joint Annual Conference, 10 November 2022

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Last November, the Bristol Composites Institute and National Composites Centre presented the 2022 BCI NCC Joint Annual Conference, which addressed some of the key engineering challenges of our time, particularly focusing on how composites will ensure a net zero future for the UK.

The conference showcased the cross-TRL work we conduct together and how we can work in partnership with industry to advance and optimise their technology developments and fast-track innovation.

The morning session included updates from the NCC and BCI on their work in Sustainability, Hydrogen and Digital and the afternoon session focused on transitional research and how the gap between the technology readiness levels can be bridged. There was also a keynote presentation from Kate Barnard (WhatBox – Consultants facilitating mutually beneficial partnerships (whatboxltd.com)) which was followed by a panel session chaired by Michele Barbour and featured Matt Scott, Valeska Ting, Evangelos Zympeloudis, Kate Robson-Brown and Musty Rampuri and sparked plenty of thoughtful discussions between guests and speakers.

The conference, which was held at the NCC in Emersons Green, Bristol, welcomed over 60 people in-person, and had an additional 40 online attendees. Details of the 2023 joint conference will be released later in the year.

Guests listening to a presentation at the conference Guests listening to a presentation at the conference

Why you should consider the EngD route for your doctorate study…

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The Industrial Doctorate Centre in Composites Manufacture (IDC) is pleased to announce that we are seeking high calibre candidates to take up one of five fully funded EngD studentships based at the National Composites Centre (NCC) – the UK’s leading mid-TRL innovation facility in composite materials.

To apply complete and submit this online form and send your CV and transcript of results to Helen.Howard@bristol.ac.uk

Why an EngD?

Patrick Sullivan, an EngD student currently based at the NCC, says

“ The ethos of an EngD is to work in industry as if you are a full time employee, fully embedded in your organisation’s system’s and structures, but to work towards your long term research and academic goal as your thesis approaches. The industry focus is beneficial for steering your research in a meaningful way, allowing greater impact and dissemination of your work. 

The appeal of an EngD is that you stay in the academic loop where innovation rules with the freedom to pursue research topics and work with world leading academics. But you are also driven by the focus of your industrial sponsor and their need to see the impact of the research on live projects. ”

As a successful applicant, you will be based at the National Composites Centre (NCC) and will work on novel, yet industrially focused, cutting-edge research, whilst following a taught programme at University of Bristol. The projects will cover a wide range of NCC’s strategic areas with a focus on using digital manufacturing with composite materials to solve urgent issues towards sustainability.

Financially it makes sense too.

Successful applicants will receive an enhanced tax-free stipend of £23,730 a year, a fee waiver and a generous allowance to support training.

 

Why the EngD works for industry.

The NCC has supported the Industrial Doctorate Centre (IDC) in Composites Manufacture for many years. Matt Scott, Chief Engineer for Capability at NCC, says

“ We find that our deep partnership with the IDC allows us to solve two pressing needs. Firstly, it gives us a mechanism to set motivated and tenacious minds on solving some of the research challenges that a commercial context by itself may not easily allow for. Secondly, it allows us to train the leaders of tomorrow towards an exciting and fulfilling career in the composites sector and beyond. ”

The topics you could be working on.

We are seeking highly motivated and committed individuals with an eye on the future, who are interested in conducting stimulating and essential industrial research and have a passion for finding sustainable solutions in areas such as:

  • Low-carbon concrete.
  • Through-Life Damage and Environmental Assessment.
  • Recycled Fibre/Matrix Interfacial Properties
  • Composite Shielding against Directed Energy Weapons
  • High-Rate Automated Deposition of CFRP for rapid production of aircraft wings.
  • Advanced Tooling for Aerospace Composites
  • Large Scale Rapid Infusion of wings.
  • In-Process Material Inspection and Verification of Aerospace Parts.
  • Digital Passport for Re-Using Aerospace Manufacturing Waste.

For more information about the topics you could be exploring visit our website here.

Professor Janice Barton, Director of the IDC, says;

“ If you are interested in studying for a doctorate at University of Bristol, being involved in the activities of Bristol Composites Institute and have a passion to explore sustainable composites solutions to address NetZero challenges then please consider applying to be part of our inclusive and dynamic programme in Composites Engineering. ”

What you need to bring.

Applicants must hold/achieve a minimum of a 2:1 MEng or merit at Masters level or equivalent in engineering, physics or chemistry. Applicants without a master’s qualification may be considered on an exceptional basis, provided they hold a first-class undergraduate degree. Please note, acceptance will also depend on evidence of readiness to pursue a research degree and performance at interview.

Due to visa restrictions these posts are available to Home/EU (UK settled status) with permanent UK residency.

To apply complete this online form and send your CV and transcript of results to Helen.Howard@bristol.ac.uk

If you have any further questions about our programme, or if you would like to have an informal chat with Professor Barton or a current EngD student, please do get in touch by e-mail.

Helen Howard, IDC Manager Helen.Howard@bristol.ac.uk

Composites for Hydrogen Storage for Green Aviation

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by Valeska Ting v.ting@bristol.ac.uk; James Griffith james.griffith@bristol.ac.uk; Charlie Brewster c.d.brewster@bristol.ac.uk; Lui Terry lt7006@bristol.ac.uk  

 

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: 
https://www.airbus.com/search.image.html?q=&lang=en&newsroom=true#searchresult-image-all-22  

References:  

[1] Hydrogen-powered aviation – A fact-based study of hydrogen technology, economics, and climate impact by 2050 https://www.fch.europa.eu/sites/default/files/FCH%20Docs/20200507_Hydrogen%20Powered%20Aviation%20report_FINAL%
20web%20%28ID%208706035%29.pdf
[2] Liquid Hydrogen–the Fuel of Choice for Space Exploration https://www.nasa.gov/content/liquid-hydrogen-the-fuel-of-choice-for-space-exploration 
[3] Airbus looks to the future with hydrogen planes
 https://www.bbc.co.uk/news/business-54242176 
[4] Liquid Hydrogen Delivery
 https://www.energy.gov/eere/fuelcells/liquid-hydrogen-delivery 
[5] Airbus reveals new zero-emission concept aircraft https://www.airbus.com/newsroom/press-releases/en/2020/09/airbus-reveals-new-zeroemission-concept-aircraft.html 
[6] Bristol Composites Institute
 http://www.bristol.ac.uk/composites/ 
[7] Nanocage aims to trap and release hydrogen on demand https://www.theengineer.co.uk/nanocage-hydrogen-gas/ 
[8] Engineering porous materials
https://www.youtube.com/watch?v=TNqLeO61huM 
[9] France bets on green plane in package to ‘save’ aerospace sector https://uk.reuters.com/article/us-health-coronavirus-france-aerospace/france-bets-on-green-plane-in-package-to-save-aerospace-sector-idUKKBN23G0TB 
[10] Germany plans to promote ‘green’ hydrogen with €7 billion https://www.euractiv.com/section/energy/news/germany-plans-to-promote-green-hydrogen-with-e7-billion/ 
[11] EU Hydrogen Roadmap https://www.fch.europa.eu/sites/default/files/Hydrogen%20Roadmap%20Europe_Report.pdf 
[12] Boris Johnson: Wind farms could power every home by 2030 https://www.bbc.co.uk/news/uk-politics-54421489  

Natural Fibre Composites Research

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Testing the Mechanical Performance of Nature Fibre Composites.

Head shot of Owen Tyley by Owen Tyley owen.tyley.2019@bristol.ac.uk; Tobias Laux tobi.laux@bristol.ac.uk; Neha Chandarana neha.chandarana@bristol.ac.uk 

Manufacturers are increasingly looking to develop new natural fibre composites (NFCs) to lower the environmental impact of structures such as wind turbine blades and automotive panelling. For these to be brought to market, their mechanical performance must be understood throughout their operating temperature range. This is ordinarily conducted using strain gauges, though the cost of purchasing and installing strain gauges makes this a relatively expensive undertaking. By contrast, digital image correlation (DIC) is an optically-based imaging technique which can determine the strains on an object such as a standardised testing coupon, at much lower cost. However, the reliability of DIC for composite coupons at elevated temperatures is not well-understood. 

Black and white photo of natural fibre composites

As part of a summer internship project supported by the Henry Royce Institute for Advanced Materials, the tensile moduli of flax- and carbon-fibre reinforced polymers using both DIC and strain gauges at temperatures up to 120°C were compared. Preliminary results suggest that the modulus as determined through DIC is the same as for strain gauges, but with greater uncertainties. It is therefore suggested that DIC could be a suitable method for determining the mechanical properties of NFCs for non-safety-critical applications, and as part of early-stage research and development for new natural-fibre composites. 

 

Flax: A sustainable alternative to glass fibres in wind turbines?

 

 

 

by Abdirahman Sheik Hassan a.sh.2019@bristol.ac.uk; Neha Chandarana neha.chandarana@bristol.ac.uk ; Terence Macquart

Flax-fibre composites have been widely praised as a high-performance sustainable alternative to synthetic fibres in the composites industry. However, as with many natural fibre composites, the mechanical properties (strength, stiffness) of flax-fibre composites do not match up to their synthetic counterparts. This study assesses the suitability of flax-fibre reinforced composites as a replacement for glass-fibre composites in the context of a wind turbine blade using a life cycle engineering approach.Research on a computer screen Finite element analysis (FEA) was used to determine the design alterations required for comparable performance, followed by a cradle-to-grave life cycle assessment to ascertain the subsequent environmental impact of these alterations. The preliminary results show a significantly greater volume of material is required in a flax-fibre blade to match reserve factor and deflection requirements; however, these models do show reduced environmental impact compared with the glass-fibre composite blades. End-of-life options assessed include landfill and incineration, with and without energy reclamation. 

 

Amphiphilic Cellulous for Emulsion Stabilisation and Thermoplastic Composites.

Headshot of Amaka Onyianta Headshot of Steve Eichhorn by Amaka Onyianta a.j.onyianta@bristol.ac.uk; Steve Eichhorn s.j.eichhorn@bristol.ac.uk

Biobased polymers, commonly referred to as bioplastics, are made from plant or other biological material instead of petroleum. They, therefore, present opportunities for the development of sustainable plastics from a wide range of pre-cursors including corn, vegetable oil and cellulose. Cellulose, the most abundant polymer on earth, is also renewable material available from vast resources such as wood, plant, bacteria and even sea animal tunicates. Considerable research efforts have been put into developing cellulose-based biopolymers. However, despite all its advantages, cellulose due to its hydrophilic (water-loving) nature presents a significant challenge with respect to blending with other polymers which are often hydrophobic (water-repelling).  

Diagram showing amphiphilic cellulose coated polypropylene composites

To address this challenge, our group is exploring surface modification of cellulose to make it hydrophobic. One such modification we have investigated results in a material that is not only hydrophobic, but largely retains the inherent hydrophilicity of cellulose, leading to an all-new class of material: amphiphilic cellulose. Due to this amphiphilic nature, the cellulose can stabilise oil-in-water emulsions, making it attractive for various applications including in the personal care products sector where consumer desire for nature-based products is increasingly driving demand.    

It is also recognised that while material sources can be sustainable, processing techniques also need to be sustainable for this credential to hold for the final product. Work within our group is therefore also looking into aqueous processing of amphiphilic cellulose with thermoplastics to yield biobased sustainable composite materials with improved tensile modulus. Moreover, the melting profile of the thermoplastic is not affected by the process, neither is a pre-step of compounding needed as seen in the traditional process for incorporation of fillers in thermoplastic composites.