Research-based Automated Deposition: A new material characterisation and process development tool

Posted on 14/06/202416/07/2024 by jo.rich

By Ege Arabul, Dr James Kratz & Dr Vincent K. Maes

Summary

A new research tool has been developed and commissioned at the University of Bristol, see Figure 1, to investigate the Automated Fibre Placement (AFP) deposition process. The machine, named “Real-Time AFP”, allows for composite pre-preg tape to be delivered onto a surface in an AFP/ATL-representative manner, where the process parameters, such as compaction force, temperature, speed and tow tension, can be varied, and the material tack can be characterised. The device also monitors the deposited tape and captures data in real time, allowing for the detection of manufacturing defects and correlation to the process parameters. The device aims to accelerate research into a wide range of AFP related topics, including novel sensor development, real-time control algorithms, and dedicated material benchmarking standard for AFP processes.

Figure 1– The newly commissioned Real-Time Automated Fibre Placement (RT-AFP) Machine in the Bristol Composites Lab (BCI).

Introduction

Automated Fibre Placement is a technique to deliver semi-finished, composite pre-preg tape onto a surface where narrow pre-preg slices are collimated on the head and delivered together through the use of a gantry head, heater, and a compaction roller. This technique is particularly well suited for gently curved or larger structures where a robust and repeatable manufacturing technique is needed, such as in aerospace applications, and where variable stiffness composites are needed such as in hyperbolic blended wing bodies, c-spars, and engine fan blades, which can be achieved through tow steering.

While automation of composite manufacturing processes has been successfully industrialised, part inspection and re-work remains a manual process, which can take up to 42% of the total time per build (Rudberg, T, “A Process for Delivering Extreme AFP Head Reliability”, 2019). Furthermore, this inspection is usually conducted only visually, which is highly dependent on the skill of the technician. Supplemented by the increasing trends in Industry 4.0 and a global emphasis on sustainability aimed to reduce waste and increase efficiency in composite manufacturing, methods to detect and react to defects during manufacturing are of great industrial interest.

The Key Features and Capabilities of RT-AFP

The in-house “RT-AFP” rig was developed to address the gap between the AFP representative lab experiments and the full-scale AFP deposition using a commercial AFP machine, which has varying degrees of process complexity, as shown in Figure 2. A key consideration in developing this machine was to ensure it provided rich, in-process deposition data, which many commercial AFP solutions would not offer for research purposes.

The key features of this machine include;

Closed-loop control over AFP parameters, such as the layup temperature, compaction force, speed and tow tension.
A real-time data capture system, including laser scanner profilometry data, to monitor the deposition process.
Material tack characterisation capability via peel-tack-testing after deposition.
Implementation of novel sensors in a modular manner.
Ability to vary process parameters on the fly and implement different setpoint profiles.

Figure 2- Varying degrees of complexity in AFP research, with RT-AFP being in the middle.

Figure 3 illustrates the key components of the machine and its operating principles. The image on the left-hand side shows the loading of the composite pre-preg tape as it is being deposited. The pre-deposition and post-deposition laser scanners scan prior to and after the tape deposition, respectively, and can be used to subtract data from one another to identify the incoming tape and any misalignment or defects on the tape. After the deposition, the deposited tape can be peeled off by running the machine reverse.

Figure 3-The key components of the RT-AFP

Success Stories and Future Outlook

The “RT-AFP” has already been a critical resource for researchers investigating the AFP process. Some highlight studies include a comparison between the AFP and hot press processes for a layer-by-layer curing technology[1], a real-time defect detection system using laser scanners with convolutional neural networks to classify different types of deposition defects [2] and a real-time process control algorithm to mitigate influence of certain defects during deposition [3].

With strong ties to sensor development teams within the university, including non-destructive testing and evaluation, the “RT-AFP” is a growing tool to accelerate research. Along with these studies, the device is also being used to correlate the process parameters to the evolution of AFP manufacturing defects to better inform our understanding, and models of the AFP deposition process and to develop novel techniques to eliminate arising defects on the fly. The research team invites future collaborators investigating the AFP process, within and external to the university, to utilise the machine to accelerate their research capabilities.

Figure 4-Summary of key success stories using the RT-AFP

Linked Articles:

Hartley, R., & Kratz, J. (2024). CFRP layer-by-layer curing using research-based automated deposition system. Manufacturing Letters, 40, 85–88. https://doi.org/10.1016/j.mfglet.2024.03.005
https://composites.blogs.bristol.ac.uk/2023/11/30/real-time-quality-control-in-automated-fibre-placement-using-artificial-intelligence/
Nguyen, D. H., Sun, X., Tretiak, I., Valverde, M. A., & Kratz, J. (2023). Automatic process control of an automated fibre placement machine. Composites Part A: Applied Science and Manufacturing, 168, 107465. https://doi.org/10.1016/J.COMPOSITESA.2023.107465

Bristol Composites Institute in Space

Posted on 14/06/202414/06/2024 by jo.rich

By Prof. Ian Hamerton, Prof. Byung Chul Kim, & Dr Vincent K. Maes

The high specific properties of composite materials have long made them of interest in space applications, where despite significant reductions over the years it still costs around $15 dollars per gramme of payload to get to Low Earth Orbit (LEO). However, significant challenges remain in terms of producing material systems capable of withstanding the harsh environments, manufacturing light weight components precisely, and developing innovative solutions to enabling future space missions. At the Bristol Composite Institute (BCI), several research activities are targeted at developments that will enable further utilisation of composites in space applications. These can broadly be grouped under three main challenges.

Challenge 1: Getting to space.

While the specific properties of composite materials are high, realising the true potential for lightweighting requires reliable defect free manufacturing as well as significant tailoring of the amount of material and orientation of fibres in different regions of the part. To this end, there have been two key developments at the BCI that promise to contribute to extreme light-weighting. WrapToR, or Wrapped Tow Reinforced, truss structured, led by Dr Ben Woods, combines the high specific properties of composites with the high geometrical efficiency of truss structures and the efficient and highly automatable wrapping process.

A manufactured tow steered cylinder In parallel, development of fibre steered composite structures, led by Prof. Byung Chul (Eric) Kim, has had several successful steps towards commercialization. Specifically, a recent academic – industrial collaborative effort, led by the European Space Agency (ESA), which designed and manufactured Rapid Two-Steered (RTS) cylindrical structure, see Figure 1, clearly shows its potential for launch vehicles, where the design focus is not on the strength but on the structural stability during launching. The produced structure was nominated for a JEC Composites Innovation award in 2022. This study, which is now being followed by an ESA-funded project to apply the same methods to a full scale space structure in collaboration with a prime space contractor, was led by Dr Rainer Groh in collaboration with a BCI spin-out company, iCOMAT, which is commercialising Continuous Tow Shearing (CTS) technology after the techniques was first developed within a BCI research project. iCOMAT are proactively engaging with the space industry having secured £4.8M from the UK Space Agency (UKSA) and very recently a further £22.5M Series A from venture capital, a rare feat for composite start-ups.

Looking forward, next-generation automated composites manufacturing technologies are needed to enable highly efficient and complex composite structures that cannot be manufactured with current technologies. At BCI, 3D CTS technologies, see Figure 2, are under development which can manufacture complex space structures such as domes and nose cones without defects (see further reading for publication).

Three people in a lab

Figure 2 – The team at Bristol developing continuous tow stearing for 3D geometries (top) with examples of standard AFP quality (bottom left) vs CTS quality (bottom right).

Challenge 2: Surviving space.

Once gravity has been overcome, the materials that remain in space will be exposed to the extremely damaging effects of atomic oxygen, extreme temperatures and thermal cycling, galactic cosmic radiation, and other challenging environmental effects. To address these challenges Prof. Ian Hamerton has led and supervised several research activities around developing new composite materials. Current projects are funded by the UK Space Agency (UKSA) and the Defence and Security Accelerator (DASA) and include collaborations with the National Composites Centre (NCC) in two high profile ESA programmes.

Initial developments began in 2017, when Oxford Space Systems funded a PhD studentship to study material survivability under space conditions. This work resulted in a family of polybenzoxazine (PBZ) nanocomposite resins, with enhanced resistance to degradation from the highly damaging effects of atomic oxygen, which has subsequently been studied in several research projects.

These developments have led to the BCI contributing four composite samples to an experiment in the Euro Material Ageing Facility on the Bartolomeo module onboard the International Space Station (ISS). The samples were prepared with UKSA funding and are based on three PBZ resins and a novel cyanate ester resin, also designed in BCI. Transportation to the ISS on a SpaceX Dragon launch vehicle is planned for the autumn of 2024; where the samples will spend up to 18 months, orbiting the Earth, before being returned for further analysis. This is part of a £3.5M Euro Materials Ageing 1 campaign (funded jointly by ESA and CNES), designed to examine the effects of the LEO environment, see Figure 3, on 45 materials drawn from 15 international teams.

A satellite in space

Figure 3 – In space materials are exposed to extreme temperatures and radiation, including charged particles which earth is shielded from by its magnetic field. [image credit: SSA, reproduced under ESA Standard Licence [non-commercial use]).

In parallel, Prof. Hamerton’s team is also conducting projects to investigate chemically modified variants of the PBZ resins for their shielding characteristics towards galactic cosmic radiation, as well as the effects of LEO on the efficiency of thin (0.3 mm) deployable laminates. Another line of research is developing self-healing variants of PBZ polymer matrices, with the aim of improving the resilience of the composites against high velocity impacts from space debris – which is an important consideration for the final challenge.

Challenge 3: Staying in space

Once the payload is in space and resilient to the harsh environment, the goal now becomes to stay there and operate for as long as possible. With space agencies shifting their focus towards longer missions and even extraterrestrial habitats, cradle-to-cradle materials and processes that enable in-orbit and off-planet repair and manufacturing will become critical. In this, both novel material and manufacturing developments within the BCI play a crucial role.

Increased use of high performance thermoplastics as well as the potential to use reclaimed fibres using the patented HiPerDiF process, currently being commercialised as AFFTTM by another BCI spinout, Lineat Composites, combined with either fibre steering technologies or the WrapToR process, may enable low cost and scalable manufacturing. The specific coupling of HiPerDiF material and the WrapToR process is the current focus of a collaborative PhD project and related proposals to extend this work have recently submitted to the UKSA and ESA. Furthermore the WraptToR process has also been adapted into an extrusion like process, known as “TrussTrusion”, which could allow for compact payloads of raw materials which are then turned into the structural components once in space, or for re-production of recycled materials into new structural elements.

Outlook

While the challenges are great, the research already carried out and current developments are providing the building blocks and cornerstone technologies needed to enable the future of space exploration and travel. Providing both improved performance and sustainability, the research at the BCI is well placed to lead the way in the 21st century.

Acknowledgements

The challenges in developing new material systems and manufacturing process for space applications are profound, so it takes the efforts of many. Within the BCI contributions have been made by PhD researchers, past and present, post-doctoral researchers, academic staff, and our collaborators around the world including colleagues at the National Composites Centre.

How can experienced professionals find research projects in their niche area?

Posted on 31/01/2024 by jo.rich

Many experienced professionals can easily find research projects in their niche area, but young PDRAs and PhD students may not know how to find them. Research projects can offer opportunities for learning, networking, and career advancement. However, finding research projects that match one’s skills and interests can be challenging. For that reason, we will introduce some strategies and resources for finding research projects in your niche area.

Identify your research interests and skills.

Identifying your research interests and skills involves introspection into your academic background, personal passions, and career objectives. Questions like, “What are the primary themes or issues that captivate me?” and “What gaps or challenges exist in my field of study?” can guide this reflection. Additionally, consider the skills or methods you enjoy using or learning, and ponder how you wish to contribute to the progress of knowledge or society.

To pinpoint your research interests and skills, explore diverse sources of information and inspiration. This may include perusing academic journals, books, or websites pertinent to your discipline. Seek input from current or past professors, colleagues, or peers who share your interests. Delve into online databases or platforms listing research opportunities or projects and explore professional associations or networks offering guidance for researchers.

To find meaningful projects, look for titles such as research assistant, research officer, or research specialist in relevant fields. Utilize keywords when searching on platforms like LinkedIn and ResearchGate to discover valuable opportunities.

Explore existing research projects and opportunities.

One of the crucial skills for a researcher is the ability to investigate existing research projects and opportunities. This skill aids in discovering new collaborators, recognizing gaps in the literature, and identifying potential funding sources. Here are some suggestions on how to explore existing research projects and opportunities:

– Utilize online databases and platforms that aggregate research information, such as Google Scholar, ResearchGate, Scopus, and others. Conduct searches based on keywords, topics, authors, institutions, or citations to locate pertinent research papers, projects, and researchers.

– Attend conferences, workshops, seminars, and webinars aligned with your field of interest. Stay informed about the latest developments, trends, and challenges in your research area while networking with fellow researchers who share your interests. Additionally, consider presenting your own work to receive feedback from peers and experts.

– Join professional associations and societies that represent your research domain. Gain access to their publications, newsletters, events, and membership directories. Participate in committees, working groups, or special interest groups to contribute to their activities and initiatives.

– Initiate contact with potential mentors, advisors, or collaborators working on topics or methods that intrigue you. Reach out through email, social media connections, or request a meeting to inquire about their current or past projects, research goals and challenges, and seek advice.

– Explore your institution’s research resources and opportunities. Check your department’s website, bulletin board, newsletter, or email list for information on ongoing or upcoming research projects, events, grants, or awards. Engage with colleagues, supervisors, or administrators to learn more about their research interests and activities.

Research out to potential collaborators and mentors

One of the key skills for a researcher involves reaching out to potential collaborators and mentors who can provide valuable feedback, guidance, and opportunities. However, many researchers face challenges in initiating and maintaining such professional relationships. Here are some effective tips for conducting research outreach:

– Clearly define your goals and interests before reaching out to anyone. Determine what you aim to achieve through collaboration or mentorship and what you can contribute in return. Whether it’s learning a new method, working on a specific project, or seeking career advice, consider how you can contribute to their research or objectives.

– Conduct thorough research on the individuals you intend to contact, including their background, publications, and current projects. Tailor your message to reflect your genuine interest and enthusiasm, and identify common connections, such as mutual colleagues, institutions, or interests, to establish rapport.

– Craft a concise and polite email for your initial contact. The first impression is crucial, so ensure your email is well-written, professional, and respectful. Briefly introduce yourself, explain the purpose of your contact, articulate what you hope to gain from the interaction, and inquire about their availability and preferred mode of communication. Be specific about your request yet remain flexible and considerate of their time and priorities. If relevant, attach your CV or portfolio, and provide a link to your website or profile.

– Follow up and maintain communication. If you don’t receive a response within a reasonable time frame, consider sending a gentle reminder or follow-up email after a week or two. However, avoid being overly persistent or pushy to prevent annoyance or pressure. If they agree to a conversation, prepare questions or topics for discussion, and be punctual, courteous, and attentive during the conversation. Express gratitude for their time and insights and follow up with a thank-you email afterwards. If they suggest any action items or next steps, promptly follow through and keep them informed of your progress.

For more information, feel free to contact the BCI internal newsletter team at uob-bci-internal-newsletter@bristol.ac.uk

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

Posted on 30/11/2023 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.

Industrial Doctorate Centre in Composites Manufacture: Showcase 2023

Posted on 30/11/2023 by jo.rich

The Industrial Doctorate Centre welcomed over 40 guests to the annual Showcase event, on the 19^th September 2023, held at the Watershed in Bristol. The event was followed by a gala dinner at Bristol Harbour Hotel.

The Industrial Doctorate Centre in Composites Manufacture has now reached its 10^th year, and over this time, 31 students have graduated with an EngD in Composites Manufacture. The day before the event we welcomed five new students to the IDC, bringing the total number of students currently enrolled to 20. The new students were excited to attend the Showcase along with existing IDC students, alumni, academic and industrial supervisors, and joined by a group specially invited VIP guests, with strong connections to the UK composites sector. It was a great opportunity for students to present their research work to a wider audience and network within the industry.

The day consisted of 3 oral presentations sessions and a quick-fire poster session all chaired by the IDC alumni. The presentations from our students ranged from topics in advanced manufacturing techniques, new approaches to testing wind turbine blades, process simulation and effect of cryogenic exposure on composites. A focus of the showcase was sustainability, this was brought in to context in a fantastic keynote speech from Dr Ffion Rodes. One of the ambitions for the IDC is for our students to create their own spinouts and companies. Dr Tomasz Garstka a PhD alumni from Bristol Composites Institute has done just that creating his company LMAT. Tomasz gave an excellent keynote presentation on how he turned his academic research into a commercial tool for composite tooling.

The Showcase ended with a very lively panel discussion, chaired by Professor Mike Hinton of the High Value Manufacturing Catapult. The panel comprised Dr Anna Scott Magma Global; Dr Petar Zivkovic Airbus; Dr Peter Giddings NCC; Dr Faye Smith, Avalon Consultancy; Professor Paul Hogg, Royal Holloway University of London; Janet Mitchell, MC²Consultants.

The panel were asked to discuss how can industrially-based doctoral research help unlock the potential of composites in achieving a Net Zero? The topics discussed included: Understanding better how digital technologies can help accelerate our learning; start thinking of composites as an enabler to protect our way of life by integrating sustainability at the design stage, creating a template for LCA that can be used in all projects; extended in-service life of composites and life extension programmes; smarter testing to reduce waste and move to virtual tests for certification; take steps to eliminate trial and error approaches in manufacturing; move away from the driven by rate approach.

The event was a great success with engaging discussions throughout the day carrying on into the evening at the reception and the gala dinner.

Professor Janice Barton, Director of the IDC was delighted with the day and said “It was fantastic to see our students present their work with confidence and realising they are making a significant difference to their sponsoring companies and to wider society”.

Process Simulation For Reduced-defect Composites

Posted on 28/11/202301/12/2023 by jo.rich

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

Posted on 28/11/2023 by jo.rich

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

Posted on 23/11/202307/12/2023 by jo.rich

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)

BCI’s Research Associate awarded Young Researcher Award at International Conference

Posted on 15/05/2023 by jo.rich

Bristol Composites Institute’s (BCI) Research Associate, Yi Wang attended the 12th Asian-Australasian Conference on Composite Materials (ACCM12) in Hangzhou, China from the 25th to the 28th of April. Yi won the Young Researcher Award for his talk entitled “An automated workflow for composites part manufacturability prediction and tooling optimisation”. Yi was presented the award by BCI’s founder and former director Professor Michael Wisnom who also attended the conference.

Four people pictured with their awards

Yi has been a member of our process simulation team for a number of years working originally as a PhD student within the EPSRC SIMPROCS platform grant before becoming a Research Associate working on the same project. He now works on our latest EPSRC grant: Composites: Made Faster. Yi’s talk presented the outputs from our work on the research program DETI led by the National Composites Centre (NCC) and funded by the West of England Authority. This research developed, at an industrial scale, an automated workflow for the prediction of manufacturing-induced defects in autoclave-moulded thick composite parts. It builds on the robust consolidation model and homogenisation approach developed at BCI in the last 10 years.

The work also laid the foundation to conduct data-driven optimisation of caul plate geometries for reduced geometrical deviation from part design. Wide adoption of these tools could allow saving industry a considerable amount of time and money by removing a large number of the many physical trials that are currently an integral part of any composite part manufacturing process development.

Yi’s supervisors Dr Jonathan Belnoue and Professor Stephen Hallett said: “Congratulations to Yi for this achievement. Yi is a very important member of the team who brings great enthusiasm to anything he puts his hand to. A very well-deserved award! This is also great recognition of the quality of BCI process simulation work that has advanced considerably over the last 10 years”.

Developing high-value lignin and cellulosic materials from animal dung

Posted on 03/05/202311/05/2023 by jo.rich

Fabrizio Scarpa and Adam Willis Perriman

A recent review work carried out at the BCI in collaboration with the Scotland’s Rural University College and the University of Edinburgh has identified several routes to obtain crude biobased materials, composites, and purified derivatives from manure. The paper is open access and can be found here: https://www.sciencedirect.com/science/article/pii/S014181302300404X?via%3Dihub

Manure can be considered as an unlikely source of biomass. It is rich in lignocellulose components like cellulose, hemicellulose, and lignin. Renewable biomasses provide a global yield of 200 billion metric tons per year of lignocellulose, yet the separation of the biobased components requires a combination of energy-intensive physical and chemical processes.
Herbivores (and ruminants, in particular) have however highly developed digestive organs able to break down the lignocellulose. Lignin reinforcements obtained from cattle dung have shown a very promising performance in terms of matrix adhesion to phenolic resins. The digestion process of ruminants like cows contributes to an enhanced surface structure of the biobased fibres, which favours bonding with different matrices.

A similar enhancement of bonding between phenolics and reinforcement obtained from elephant dung is not however present. Elephants are monogastric and lack the foregut fermentation that cows provide. The diversity of the bio chemo-physical origins of animal manure therefore constitutes a challenge to manufacture composite materials with unique production processes. Nevertheless, composites made from animal manure components are mixable with a wide variety of thermosets and thermoplastics, making them appealing for secondary load-bearing applications across the industries.

Quite significantly, manure could be used to extract nanocellulose, which it has a huge potential for use in a wide variety of applications, from structural to antibacterial agents, fuel cells, and biomedical applications. Current production methods of nanocellulose are energy intensive, while the use of enzymes in biomass has been hailed as a low-cost methodology for production. Animal ruminants and in particular cattle can provide an alternative way to produce at larger scales nanocellulose and other lignocellulose-based components, because we can make use of the existing large-scale supply chain in the agricultural and livestock business existing in the UK and beyond. Never has the old saying: “Where there’s muck, there’s brass” sounded truer.”

Category: Postgraduate Research