Process automation - automated fibre placement

Automated Fibre Placement is the current industry standard process for manufacturing large critical structures for the aerospace industry. It involves depositing heating multiple reinforcement tapes and applying them under tight control onto the mould tool surface using industrial robots. We carry out fundamental studies of the AFP process in ACCIS and collaborate closely with the National Composites Centre through EngD students from the Industrial Doctorate Centre in Composites Manufacture at higher TRLs.

Contact: Professor Kevin Potter

Process automation - robotics and cobotics

The manufacturing of high quality composite products typically takes one of two routes; entirely manual hand layup, or entirely automated tape laying. A third approach is possible, whereby human-robot collaborative layup processes are developed, utilising the best aspects of both approaches. Our aim is to combine the cognition and awareness of a human worker with the mechanical capabilities of a robotic system. It is achieved by splitting the overall layup process for a given mould surface into individual tasks which are allocated to either the robot or human, matching the task requirements with the respective capabilities of either entity. The effects of the collaboration on the layup process and the user experience are improved quality, reduced need for vacuum consolidation, and reduced worker fatigue.

Examples of activities during the human-robot collaborative layup process. A: Static robot arm supporting the ply while the human has both hands free to complete layup; B: Human completing a portion of the layup that involves high in-plane deformation, and; C: Robot using an end effector to consolidate the ply onto the mould.

Contact: Dr Carwyn Ward

Continuous tow shearing

Fibre steering is essential to manufacture more advanced composite structures and complex shapes with high quality. However, the current AFP technologies always produce fibre wrinkling defects when bending the fibre tow to steer its direction. Continuous Tow Shearing (CTS) technology overcomes this limitation by utilising in-plane shear deformation of the tow, which can eliminate such defects and significantly reduce the minimum fibre steering. We are currently focusing on scaling up this technology for industrial applications and advancing its capability for more complex 3D structures.

Contact: Dr B.C. Eric Kim

Graded multi-matrix composites

Polymer composites face a wide range of limitations due to the nature of constituent materials, especially matrices. Because of the matrix performance, they suffer from intrinsic brittleness, prone to damage, processing defects, and functional constraints. Localised loads are known to be a particular curse of composites. Stress concentrators, such as mechanical fasteners, joints, inserts, corners, unavoidable in any real structure, cause premature damage development and accelerated failure. New generation of structures will be made of complex multi-material systems where individual sets of properties will be designed and assigned to every elementary volume of the structure. We look at various methods of incorporating dissimilar matrices in one integrated composite system through local deposition / print of reactive additive-rich resin into continuous reinforcement, tailored consolidation procedure, and positioning of particles through external magnetic field.

Contact: Dr Dmitry Ivanov

Defects in composites manufacturing

Any manufacturing process can generate defective parts, we need to understand how defective parts are generated, what controls the generation of defects, how the variability in materials and processes leads to defects, how incipient defects can be detected during the process, and what impact the defects might have on mechanical performance. We use a variety of techniques such as defect taxonomy, in-process investigations and CT scanning, alongside process modelling and performance evaluations under static and fatigue loadings to understand the impacts of defects.

Contact: Professor Kevin Potter‌

Understanding lay-up processes

Despite the introduction of automated processes, manual layup remains a crucial and widely used process in composites manufacture. Even so it remains a relatively unknown and undocumented process that has changed little the last 30 years. In order to meet increasing demand, composites manufacturing needs to evolve into an optimised, leaner process; but to begin this it is arguable that it is first necessary to build greater understanding of the existing benchmark process of hand layup. We have, with influence from other multidisciplinary sources, conducted in-depth and detailed analyses of the layup process; exploring the laminator-material-mould interactions, use of tools, and instruction processes. It has led to the development of a unique knowledge-base of common laminating techniques - enabling detailed instruction, training, and improved performance.

A recording of a laminator forming a ply to a mould surface. Frame by frame analysis of such examples enabled the development of a unique knowledge base that gives in-depth understanding to the hand layup process.

Contact: Dr Carwyn Ward

Manufacturing Process Modelling

The final properties and geometry of composite structures are strongly affected by the manufacturing processes involved. In many cases these processes can also introduce variability into the material properties due to the large number of process parameters that are involved. Numerical modelling is an effective tool to study, understand and predict the underlying mechanisms of defect formation and influence of process parameters. At the Bristol Composites Institute we have developed a suite of finite element tools for the prediction of prepreg consolidation, which is an important mechanism in the formation of wrinkles in thick composite parts. We have also extensively studied textile preform deformations and created numerical tools for the prediction of internal fibre architectures and drape simulation. In the future it will be possible to use these tools as part of a component design and manufacture cycle, leading to optimised quality, reduced defects and increased production rates. 

Contact: Professor Stephen Hallett

Design for Manufacture

In order to reduce costs while maintaining high quality in the manufacture of composite structures, either low cost manufacturing methods will need implementation or parts will have to be designed with manufacturability in mind. We research Design for Manufacture (DfM) by employing standard industrial approaches (Boothroyd and Dewhurst), as well as developing novel predictive capacity systems capable of intelligent design processes that take manufacturing guidelines earlier into the design phase. These novel systems utilise geometric features to return a complexity factor that predicts the expected time to drape a feature or the total mould surface. Both systems rely on using our bespoke in-house kinematic drape simulation/instruction software, as well as standard material behaviour tests; and have proven accurate for their implementation on various geometric features.

The effect of an increasing ramp angle on the proportion of a feature area covered by the ply.

Contact: Dr Carwyn Ward

Supporting manufacturing via Virtual and Augmented Reality tools

We have combined our developed knowledge bases in hand layup understanding, automation/ cobotics, and Design for Manufacture, with low cost but efficient digital tools and gaming technology to better support manufacturing. In particular we have concentrated on training due to the skills shortage risk, which could be extremely hard for SMEs to address. One particular example is that of LayupRITE, which applies Augmented Reality through the use of affordable tracking and projection technologies, to dynamically guide a laminator during a layup. We are able to offer improvements in quality and standardisation alongside reductions in training time, layup time, and labour costs; which is made possible as rather than approaching design and manufacture as the typically sequential process used we recognise and adopt a circular process.

Circular design and manufacturing flow, as the basis for use of Virtual and Augmented Reality Tools within composites manufacturing.

Contact: Dr Carwyn Ward

Composites recycling

Waste can be generated at every step in the manufacture of composites structures with large amounts of waste being associated with cutting out plies from sheets of reinforcements, through trimming of mouldings through to structures reaching the end of their working life. Our primary focus has been on rebuilding value in materials recovered from in-process wastes. We are now investigating closed loop recycling of aligned short fibre composites to solve the composite waste problem with a new material solution to an old manufacturing problem.

HiPerDiF (High Performance Discontinuous Fibre) technology, invented at the University of Bristol, produces highly aligned discontinuous fibre composites (ADFRCs) with the goal of addressing the issues of the composite industry - manufacturing and recycling. ADFRCs have the potential to offer mechanical properties comparable with those of continuous fibre composites Moreover, ADFRCs produced using HiPerDiF have demonstrated the capabilities to overcome three of the key limitations of conventional continuous fibre composite materials: the lack of ductility, i.e. their elastic-brittle behaviour, by hybridising different types of fibres (e.g glass, carbon) or exploiting pull-out mechanisms; the difficulties in producing defect-free components of complex shape with high-volume automated manufacturing processes; and implementing a sustainable material lifecycle, e.g. the integration of production and end-of-life recycled waste in a circular economy model.

Click here for more information on HiPerDiF technology and the potential benefits.

Contact: Professor Ian Hamerton