Category: Research

Optimisation of multi-rotor wind turbines for reduced cost of energy and environmental impact

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Abdirahman Sheik Hassan, Neha Chandarana, Rainer Groh, Terence Macquart

The Big Picture

Multi-rotor wind turbines (MRWTs/MRs) are a promising solution to many of the problems facing the wind energy industry in its mission to scale up renewable capacity and address the ongoing climate crisis. MRWTs use an array of smaller rotors on one support structure, as shown in Figure 1, in place of the ever-growing single-rotor concept. The inherent scaling advantage of this architecture can offer significant mass and cost savings, while simultaneously alleviating challenges in transportation, manufacture and aeroelastic stability associated with large wind turbine blades. From the launch of the OceanX dual-rotor platform in China, to the planned construction of the Wind Catching demonstrator in Norway, the concept is moving up the technology readiness levels from theoretical economies of scale to practical solutions. While these demonstrators will shed light on the practical feasibility of the concept, little is known about the true extent of the benefit it can offer over the existing single-rotor paradigm.

Figure 1: Mingyang OceanX dual turbine platform [1] and Wind Catching System’s Wind Catching Demonstrator model [2].
Our Research Aim

Our work aims to provide further confidence in the feasibility of the multi-rotor concept through detailed modelling, analysis and by employing coupled aeroelastic optimisation to minimise the levelised cost of energy. We recently published a review on multi-rotor technology (tinyurl.com/4b4pnypm) and highlighted the need for comprehensive design studies to quantify the benefits of the multi-rotor concept in comparison to conventional designs.

An Open-Source Library to Support Research in the Multi-Rotor Concept

To address this gap, the ATOM aeroelastic software package from the University of Bristol has been expanded to model and design MRWTs, using blade element momentum theory coupled with multi-body dynamic finite element analysis. Enabling this process requires detailed virtual rotor models fit for the MR context. We tackled this problem with our recent work presented at the Multi-Rotor Seminar in Hamburg (tinyurl.com/4vpwbp64) on the generation of an open-source library of reference rotors for use in MRWT modelling. Optimised rotor models with ratings ranging from 100kW to 1MW are generated and shared in the OpenFAST format, allowing researchers to study and compare a large range of multi-rotor configurations.

Holistic Concept Design

Aiming to achieve a “globally optimised” MRWT, the individual rotor-level optimisation enables the assessment of optimal rotor number for a given overall rated power. Figure 2 demonstrates the use-case of these models – the ability to assess the optimal number of rotors by rapidly exploring a large number of different configurations with detailed rotor and support structure models.

Figure 2: Multi-rotor models constructed using rotor designs from the rotor design library. These include three 1 MW rotors, fifteen 200 kW rotors and seven interpolated 428.6 kW rotors.

An Opportunity for Greener Wind Energy

Working in collaboration with the National Composites Centre we are exploring the potential of MRWTs as an enabling technology for the use of sustainable materials in wind turbine blades, due to their smaller rotor size and reduced structural requirements. Ongoing work investigates the dual-objective optimisation of the rotor models in the rotor design library for the minimisation of both cost of energy and environmental impact.

 

[1] Mingyang Smart Energy. Retrieved October 2nd, 2025, from https://en.myse.com.cn/

[2] Wind Catching Systems. (n.d.). Retrieved September 23, 2025, from https://www.windcatching.com/

BCI develops composites manufacture simulation software: SimTex

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SimTex is a fast simulation software developed at the BCI for composites manufacture. It contains modules for simulating 2D/3D weaving, braiding, filament winding and forming. SimTex can predict the as-manufactured component geometry and identify the onset of defects, thereby helping to enable right first time manufacture in prototyping of composites parts. It is currently deployed across a number of industry projects to support composites design for manufacture.

If you are interested to learn more about the SimTex software, please reach out directly to Stephen.Hallett@bristol.ac.uk.

InVIsion Carbon, an NCC Technology Pull-Through Project: In-process NDT for Higher Quality and Rate Automated Composites Manufacturing

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Ege Arabul (BCI, University of Bristol), Per Saunders (Metrology, NCC), Robert Hughes (UNDT, University of Bristol) 

As industries like aerospace, automotive, and renewable energy increasingly rely on high-performance carbon fibre composites, ensuring these materials are made perfectly – without defects – is more important than ever. 

Current inspection methods mostly rely on visual checks or tests carried out after manufacturing is complete, when fixing problems is too late. 

Our team at the Bristol Composites Institute (BCI), working with the National Composites Centre (NCC) and the Ultrasonics and NDT (UNDT) research group, has developed a new type of sensor that can spot issues during manufacturing, before the part is finished when remanufacture is more easily performed. 

This Bi-directional Differential Eddy-Current Testing (ECT) Sensor uses the natural conductivity of carbon fibres to detect changes in how the fibres are laid down, revealing tiny gaps, overlaps, wrinkles, and other defects in real time. 

We’ve successfully tested the sensor within the Hydrogen Tank and Automated Tape Laying manufacturing cells at the NCC, where it was able to identify and help correct defects as they appeared – saving time, reducing waste, and improving production quality. 

This innovation marks a major step toward real-time, in-process inspection in composite manufacturing, cutting out costly post-production testing. 

The work now continues within the FENDER project, where we’re inviting industry partners and researchers to join us in shaping the future of smart, automated composite manufacturing. 

BCI speaker agenda – ICCM24

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Bristol Composites Institute are attending this year’s ICCM24 in Baltimore, Maryland between 4-8 August.

Five people standing in a exhibition booth smiling at the camera
Members of BCI and NCC at ICCM24.

In partnership with NCC – Innovating for Industry, BCI will be on booth 208 in the Main Hall.

You can also watch the below technical presentations from BCI speakers across the week:

Monday 4th August

4:30pm EDT, Room 309: Testing and Progressive Failure Modelling of a Wind Turbine Blade Spar Capweb Joint Substructure Dr Tobias Laux – University of Bristol.

 

Tuesday 5th August

9:35am EDT, Exhibit Hall C: Welcome Remarks and Introductions to CerTest special session: Certification for Analysis Workshop, Prof Ole Thomsen – University of Bristol

9:55am EDT, Room 309: Effect of Clamping Force and Environmental Conditioning on the Mechanical Performance of Bolted Composite Laminates Dr Neha Chandarana – University of Bristol

10:10am EDT, Exhibit Hall C: Imaging Based Sub-Structure Testing and Data Fusion Methodologies for Integration of Virtual and Physical Data Prof Janice Barton, Prof Ole Thomsen – University of Bristol

4:10pm EDT, Exhibit Hall C: Wrap Up/Closing Comments Prof Ole Thomsen – University of Bristol

4:10pm EDT Poster Session: Development and Characterisation of Bamboo and Natural-Fibre Composite-Wrapped Tow-Reinforced Trusses
Poster Presenter: Matthew Lillywhite – Bristol Composites Institute. Authors: Benjamin Woods – University of Bristol, Byung Chul Kim – University of Bristol, Terence Macquart – University of Bristol

 

Wednesday 6th August

9:35am EDT, Room 317: Is There a Hybrid Effect in Tensile and Compressive Failure of Carbon Fibre Composites Prof Michael Wisnom – University of Bristol

9:55am EDT, Room 318: Incorporation of High-Fidelity Experimental Data into Finite Element Models for Enhanced Comparison and Analysis Dr Meng Yi Song – University of Bristol

11:30am EDT, Room 319: Combined In-Situ Microscopy and Acoustic Emission Monitoring of Transverse Cracking in CFRP Cross-ply Laminates Mr Spyridon Spyridonidis – University of Bristol

2:45pm EDT, Room 319: Application of Infrared Imaging to Reveal Hidden Defects in CFRP Laminates Prof Janice Barton – University of Bristol

3:05pm EDT, Room 310: Characterisation of Embedded Channel Networks in CFRPs for Active Cooling Mr Toby Wilcox – University of Bristol

 

Thursday 7th August

10:15am EDT, Room 317: Integration of Fuzzy Carbon Overbraids into Structural Members for Improved Compressive Performance Dr Laura Rhian Pickard – University of Bristol

11:00am EDT, Room 310: Programmable Shape Transformation in Multilayer Fiber Composites Through 4D Printing Mr Erdem Yildiz – University of Bristol

11:20am EDT, Room 319: The Effect of Optical Fibre CrossSectional Shape and Microstructure on Out of Plane Strain Sensitivity in Flexible Photonic Sensors Dr Robin Hartley – University of Bristol

3:05pm EDT, Room 317: he Experimental Investigation of the Compressive Performance of Pultruded Rod Composite Struts Dr Bohao Zhang – University of Bristol

 

Friday 8th August

9:45am EDT, Room 317: Laminate Hybridization using High Modulus Carbon Thin Plies for Enhanced Compressive Performance Mr Yousef Rifai – University of Bristol

11:0am, Room 307: Differential Eddy Current Sensing Probe and It’s Implementation in Automated Composite Manufacturing Applications Mr Ege Arabul – University of Bristol

Freezing Failure: Understanding failure of composites at cryogenic temperatures

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by David Brearley

The advancements of magnets used in magnetic resonance imaging (MRI) have led to the incorporation of glass fibre reinforced polymer (GFRP) rings being adhesively bonded between epoxy-infused coils of superconducting wire. The two components respond differently to various loading conditions, potentially leading to structural failure. The magnet’s structure is integral to its’ performance as large electromagnetic forces (EMF) are induced due to the strong magnetic field present, under cryogenic temperatures. Unintentional quenches can be triggered by localised heat generated by friction or crack propagation. This results in Ohmic heating, boiling the surrounding liquid helium and potentially causing permanent, catastrophic damage to the magnet.

At the Bristol Composite Institute, the deformation and failure modes of an MRI magnet during operation were investigated by developing an experimental methodology for applying thermomechanical loads to test coupons, effectively mimicking MRI magnets in use. A simple finite element (FE) model of the magnet was constructed to assess the operational stress state and showed that high bi-axial stress concentrations were predicted around the adhesive bond between the coils and GFRP spaces.

To investigate how this could lead to structural failure, a Modified Arcan Fixture (MAF) as shown in Figure 1 was implemented. Several loading hole pairs were used to induce various compression-shear stress states in specimens that contained the adhesive joint cut from a full magnet. In the development of the experimental methodology, a more predictable bonded structure was manufactured using the coil infusion resin as an adhesive to simultaneously evaluate the epoxy’s isolated load response and refine the experiment. Tests were carried out at room and cryogenic temperatures so the thermomechanical load carrying capability of the bond could be evaluated.

Constant cryogenic cooling during quasi-static loading was achieved with the development of a novel modular cryostat that isolates the region around the adhesive bond from the rest of the fixture. The implementation of this cryostat facilitated the use of digital image correlation (DIC) to continually record the specimens’ full field response to the load at cryogenic temperatures, using just boiled pressurized nitrogen as the coolant. Based on a concept from NCC, a rapid prototyping approach was used to iteratively improve the design of the 3D printed cryostat, and in doing so, achieved test temperatures down to -150oC while maintaining the necessary optical clarity.

Figure 1 – Schematic of the Modified Arcan Fixture (left) and the author conducting multi-axial tests with it (right).

This research has improved the understanding of how adhesive bonds, of a similar geometry to those found within an MRI magnet, respond to various bi-axial stress states at room and cryogenic temperatures, see Figure 2. The design process for the developed cryostat opens the door to countless potential possibilities for mechanical testing under cryogenic conditions, where complex thermomechanical stress states require advanced measurement techniques to evaluate the material’s load response.

Figure 2 – Load carrying capability of specimens containing the adhesive bond found within an MRI magnet (circles) and that of adhesively bonded steel plates (crosses, with yield profiles as dotted lines) at ambient (red) and cryogenic (blue) temperatures for various Modified Arcan Fixture load configurations: shear (α=90 ̊), compression-shear at a ratio of 1:2 (α=120 ̊), and of 2:1 (α=150 ̊ )

Composite Process Modelling to Fast-Track the Adoption of New Materials

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Fibre-reinforced composite manufacturing is highly sensitive to input variability (e.g., fluctuations in areal weight, tow misalignment, or inconsistent binder distribution) [1] which can lead to defects during preforming and subsequent steps. This sensitivity has long hindered the industrial deployment of process models, due to concerns over their predictive accuracy. However, recent work at BCI addresses this challenge by focusing on preforming process modelling, specifically how variations in the architecture and properties of dry textile reinforcements affect fabric deformation during forming. By embedding stochastic material descriptions into finite element forming models, we have demonstrated that it is possible to design robust forming processes that consistently deliver high-quality outcomes even when upstream variability is present [2]. This enables the definition of forming windows that are insensitive to material noise, thereby reducing defect rates and increasing confidence in preform quality. Crucially, one key conclusion from this work is that process models do not need to be perfectly accurate to support optimisation and that capturing the right trends is often enough.

This modelling philosophy becomes even more important when considering sustainable composite systems. In a recently completed PhD project focused on the processing of environmentally friendly materials (i.e., recycled carbon fibres and low-impact resins [3]) we demonstrated that upfront digital design accounting for manufacturing constraints, can significantly accelerate the development of viable processing conditions for new materials (see Figure 1). The same study also confirmed that recycled feedstocks tend to exhibit inherently higher variability. While this challenge remains unresolved for now, it is clear that the modelling strategies developed in the aforementioned study will be valuable here too.

The concept of using physics-based modelling not only to predict outcomes but to enable variability-aware process design will be advanced further in one of the workstreams of a recently announced EPSRC Prosperity Partnership. We strongly believe that wider industrial adoption of new composite systems (which is critical to deliver the net-zero agenda) will not be possible without a much greater reliance on process simulation. This, however, requires a paradigm shift whereby we stop chasing perfect models and start embrace “good enough” models [4].

References:

[1] Chen S., Talokder T., Mahadik Y., Thompson A. J., Hallett S. R. and Belnoue J. P.-H. (2025). Preform variability propagation in non-crimp fabric (NCF) forming, Composites Part B: Engineering, 299:112418, https://doi.org/10.1016/j.compositesb.2025.112418.

[2] Chen S., Thompson A. J., Dodwell T. J., Hallett S. R. and Belnoue J. P.-H. (2025). A comparison between robust design and digital twin approaches for Non-Crimp fabric (NCF) forming, Composites Part A: Applied Science and Manufacturing, 193:108864, https://doi.org/10.1016/j.compositesa.2025.108864.

[3] Yavuz B.O., Hamerton I., Longana M.L. and Belnoue J. P.-H. (2025). Modelling the tensile behaviour of aligned discontinuous carbon fibre thermoplastic matrix composites under processing conditions, Composites Science and Technology, 269:111252, https://doi.org/10.1016/j.compscitech.2025.111252.

[4] Belnoue J. P.-H. and Hallett S. R. (2024). Process models: A cornerstone to composites 4.0, Composites Part B: Engineering, 283:111621, https://doi.org/10.1016/j.compositesb.2024.111621.

Figure 1: Upfront digital design accounting for manufacturing constraint allowed defect-free closed mould forming of 0/90 HiPerDiF carbon fibre/PLA preform. In the baseline case, variability in the preform is responsible for the model to predict preform failure in slightly different places to that in the real preform.

Bristol Composites Institute researchers explore novel joining strategy for modular wind turbine blades

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Research into novel hybrid joining concepts for segmented composite blades aims to inform the development of modular wind turbine technologies, supporting the industry’s pursuit of larger, more efficient blade design solutions.

As offshore wind turbines grow larger to improve energy capture, the design of wind turbine blades faces mounting challenges. Blade lengths now exceed 100 meters, especially in offshore applications, enhancing energy capture but complicating manufacturing, transport, and assembly. Traditional full-length blade construction is costly and logistically demanding, prompting the industry to explore modular blade designs.

Image showing blade joint concept and stress flow through the joint components across a segmented blade section.

Segmentation of blades, particularly spanwise segmentation i.e. splitting the blade into manageable-sized sections along its length—has emerged as a promising solution to mitigate these challenges. However, re-joining split blade sections while preserving structural integrity and performance comparable to a monolithic blade remains a significant engineering challenge. Existing solutions like mechanical fastening or adhesive bonding offer partial relief but are hindered by trade-offs such as added weight or complex assembly procedures.

To address this challenge, a research team based at the Bristol Composites Institute, University of Bristol, has developed a hybrid adhesive snap-fit joint concept tailored for wind turbine blades. This novel design integrates the alignment and retention features of snap-fit mechanisms with the smooth load transfer capability of adhesive bonding. The resulting joint design is lightweight, scalable, and easier to assemble on site, offering a compelling alternative to conventional joining methods.

This innovative hybrid joint is designed in such a way that the joint components are embedded into the critical load-bearing spar cap region of the blade, where it redirects load paths through the snap-fit joint features while preserving the aerofoil’s outer geometry. Maintaining the external blade profile allows the joint to be incorporated without compromising aerodynamic performance or requiring major design alterations to existing blade moulds, thereby supporting backward compatibility with current manufacturing processes.

Advanced finite element analysis (FEA), incorporating anisotropic composite material models and failure criteria, has demonstrated the joint’s ability to handle extreme load conditions representative of a 10 MW reference blade.  The results showed that the joint can sustain design loads without material failure all while introducing less than 1% additional weight compared to a monolithic blade, representing a significant improvement over conventional joining methods. While further investigation is needed, including prototype building and fatigue loading evaluation, this study represents a significant step toward scalable and manufacturable joint solutions for modular wind turbine blades.

 

Further Information:

The hybrid adhesive snap-fit concept has broader relevance and could inform future joining strategies for composite structures across other engineering applications. Realising its full potential, including prototype development, will require collaborative efforts, and the research team welcomes engagement from industry and academic partners interested in advancing this work toward practical implementation.

Research Team:

Muhammad Basit Ansari, Dr Vincent Maes, Dr Terence Macquart, Dr Eric Kim, Dr Alberto Pirrera To learn more or explore collaboration opportunities, please contact

Muhammad Basit Ansari

basit.ansari@bristol.ac.uk

Composites Meets Particle Physics at the Forum on Tracking Detector Mechanics

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On 16th June, in beautiful Bristol sunshine, experts from across the world arrived for the Forum on Tracking Detector Mechanics, co-hosted by Bristol Particle Physics and Bristol Composites Institute.  Particle Physics and Composites might not seem like the most obvious combination- so why spend a week talking about it?

The Compact Muon Solenoid (CMS), photo by CERN

Particle physics experiments such as those in the Large Hadron Collider seek to detect subatomic particles created in high energy collisions.  These experiments involve many layers of detectors around the collision point.  In order to detect and measure the particles as precisely as possible, physicists do not want the support structures, cooling pipes or similar to scatter or absorb them.  This is quantified by the material property radiation length – the average distance of travel by an electron through the material in which the electron energy reduces by a set factor (1/e).  The structures need to have a low material budget (measured as the fraction of a radiation length) while supporting significant load – our composites are perfect for this, particularly carbon fibre reinforced polymer structures.

Diagram showing components of CMS, image by CERN

The collaboration between BCI and CERN began some years ago with a request to help with a challenge.  The detector electronics produce significant heat, so need cooling.  At the moment this is done by pumping coolant through pipes attached to the composite plates the detectors sit on.  In addition to being extra material which might scatter or absorb the particles, these pipes have a different coefficient of thermal expansion to the composite, so when the temperature changes – such as by heating from the detector electronics – pipe and panel expand different amounts, which causes damage and makes the cooling less efficient.  CERN is interested in changing this, instead making integral channels within the composite plate – like the veins of a leaf.  This can be done by including a filament between layers of carbon fibre, which is vaporised off to leave a channel through the composite – but their channels were bursting at far below the target pressure.

My work on the NextCOMP programme provided a possible solution – ‘fuzzy carbon’ micro braids had been used to reinforce pultruded rods for nature-inspired novel composites.  Braiding over the filament before it is integrated into the composite and vaporised results in a reinforced channel – and holds approximately 10 times the pressure.  This collaborative work was funded by the University of Bristol Career Development Fellowship and International Strategic Fund, and led to a discussion regarding a wider collaboration.  A workshop followed – funded by Bristol International Research Collaboration Activities – then we were honoured by a request by the particle physics community to host the Forum on Tracking Detector Mechanics in Bristol, to build better links with our composites community.

We took the opportunity to show off some of the best Bristol has to offer.  The city gave our visitors a glorious welcome with sunshine and balloons during the Welcome drinks at the Sky Lounge atop the Life Sciences building. On the technical side, tours of NCC, Bristol Digital Futures Institute, Bristol Composites Institute and Bristol Particle Physics were well received and led to some fascinating discussions regarding possible future work together.  Could a digital representation of the experimental hardware be helpful in design, maintenance, upgrades?  Will lightweight trusses or tailored fibre placement form the structures of the next generation of particle physics experiments?

Judges inspect some of the posters

Olivia Stodieck of iCOMAT impressed us with a fascinating keynote address about Rapid Tow Shearing and its applications – particle physics experiments may soon be added to the list.  iCOMAT is a spin-out from Bristol Composites Institute commercialising research led by Eric Kim, not only amazing in its own right but also a great example of how our research can get out into the world and change it.

The technical programme included a range of fantastic talks and posters on topics including cryogenics, precision manufacturing, design of lightweight structures, cooling systems and repair when something has gone wrong!  Congratulations to Massimo Angeletti of CERN for the award for best presentation; Cristiano Turrioni of INFN Perrugia and BCI’s David Brearley for the poster prizes.

Group photo at the conference dinner

Our conference dinner at the SS Great Britain was a particular highlight, with a fascinating technical talk regarding Brunel’s famous ship, her many configurations and the conservation process from conservation engineer Nicola Grahamslaw.  Attendees took the chance to explore the ship, observe the balloons flying over and sample some of Bristol’s best pubs afterwards.  Many delighted in the opportunity to find as many Banksys as possible during their time in Bristol, visited the Clifton Suspension bridge and spent time in museums, and we heard plans to come back both for work and pleasure.

Running an international conference is no small feat, so huge thanks to Joel Goldstein, Emma Woodland, Megan Worrall and Robert Oxford Pope, plus everyone who volunteered their time for the tours.  Robert, a CoSEM CDT student, is further developing the work on microvascular channels for detector cooling and is co-supervised by BCI and CERN.

Hypothesis: If you give conference attendees an umbrella, it will be sunny all week

This event demonstrates how a small collaboration can grow and has the potential to become much more.   Bristol Composites Institute and Bristol Particle Physics are both now signed up to a larger international collaboration, coordinated by CERN, to develop the next generation of detector mechanics and we are actively working with partners in the UK and beyond.  The challenges of building tracking detectors are relevant to many other industries – extreme lightweighting, integrated cooling, precision manufacturing, vibration control, materials for extremes of temperature and radiation to name but a few. We are putting together our plans for the collaboration now – this is the time to get involved.

If this is of interest to you, contact Laura.Pickard@Bristol.ac.uk

 

 

 

 

PhD research: David Brearley

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This block, cut from an MRI magnet, consists of an epoxy-infused, insulated copper wire (embedded with filaments of Nb-Ti) spool. The epoxy binds the wires to maintain the structure’s shape, and the copper is used as an electromechanical support for the filaments, which gain superconductive properties when cooled with liquid helium to 4K (-269oC).

The combination of high operational current  (500A, similar to 50 kettles) and a strong magnetic field result in large electromagnetic forces, equivalent to the maximum take-off weight of Boeing 747!

These forces have the potential to cause crack propagation in the epoxy, releasing energy that could significantly increase the local temperature of the wire, meaning it is no longer superconductive. If this happens, the stored current is released, resulting in a rapid chain reaction where the entire magnet undergoes a “quench”.

During the quench, the massive amount of stored electrical energy transforms into heat, causing rapid boil off of the surrounding liquid helium, which is very expensive and, if not vented properly, potentially dangerous to the patient receiving the MRI.

My project aims to get a better understanding of the composite material’s failure initiation, post manufacture, due to operational cryogenic exposure and mechanical loads. My next steps are to examine the combined shear-compression loading effects on the material under cryogenic conditions and use this to inform a model that can predict quench-initiating crack propagation loads.

~ David Brearley, PhD, Aerospace Engineering

Success Through Alignment

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A test idea was developed into a confirmed proof-of-concept with experimental results in 3 months. We co-created a quick testing method for recycled carbon fibre material, reducing test time from hours to minutes.

Lineat Composites: Lourens Blok, Gary Owen

University of Bristol: Axel Wowogno, Robin Hartley, Benoit Welch, James Kratz

Background

Lineat is a BCI spin-out creating a new recycled carbon fibre material by re-aligning chopped waste fibres into highly aligned fibre tapes that mimic the architecture of virgin continuous fibre materials. The process is well suited to deliver carbon fibre materials circularity needed to meet Net Zero. An Accelerated Knowledge Transfer project was awarded by Innovate UK to evaluate what can be achieved through academic/business collaborations.

Challenge

Short aligned fibre materials can reach similar performance as continuous fibre materials, but it is highly dependent on the level of fibre alignment which can be more variable than long fibre materials. As a consequence, variable fibre orientation may arise leading to reduced volume fraction, leading to undesirable properties. A relatively high compaction force may mitigate some of these issues, but can also be an indicator of alignment quality. In this project, Lineat and Bristol worked together to evaluate if a quick and easy compaction test can reduce cumbersome quality control processes from hours to minutes.

Outcome

Lineat made a selection of recycled short carbon fibre tapes to varying degrees of alignment. The materials were prepared into samples and tested at the University of Bristol to identify the best set-up for a potential quality assurance process. The different test methods were assessed for ease of implementation. The methods were able to successfully discern poorly aligned materials straight away, however, medium and well aligned materials initially seemed similar and required development of an alignment indicator (see Figure 1). Mechanical tests and microstructure observations were used to confirm the alignment results.

 

The project performed three main activities with over 100 experimental tests performed over three months:

1) Develop a compaction test method – A compaction test method was developed and tested at different conditions to indicate alignment.

2) Perform compaction and sample testing –  Once the method was set, the compaction response was measured for different material alignment levels.

3) Correlate properties with fibre alignment – Fibre microstructure and mechanical properties were measured to demonstrate statistical relevance as quality indicator.

Impact

An innovative quality control test to quickly and accurately indicate the level of fibre alignment in recycled short carbon fibre tapes made by Lineat. Initial settings for test sample preparation, testing machine configuration, data analysis instructions, and representative plots for comparison were developed for the business.

Lineat has started an internal project to implement the test method into their production environment and use the testing method to improve manufacturing processes. The outcome is expected to have a significant influence on the uptake of recycled carbon fibre materials.