Defect Detection and Imaging in Composite Structures Using Magnetostrictive Patch Transducers

The use of thin magnetostrictive patches to generate and detect guided waves within the composite samples is investigated for defect detection. This approach has been implemented using SH0 shear horizontal guided waves in both CFRP and GFRP plates. A magnetostrictive patch transducer was able to generate SH0 waves with known directional characteristics. The synthetic aperture focusing technique (SAFT) was then used to reconstruct images of defects using multiple transmission and detection locations. The results for imaging defects in both types of material are presented.“NDTonAIR” Marie Skłodowska Curie Training Network in Non-Destructive Testing and Structural Health Monitoring of Aircraft structures (MSCA-ITN) under the action H2020-MSCA-ITN-2016- under Grant number 722134

Defects and uncertainties of adhesively bonded composite joints

© The Author(s) 2021. The increasing use of fibre reinforced polymer composite materials in a wide range of applications increases the use of similar and dissimilar joints. Traditional joining methods such as welding, mechanical fastening and riveting are challenging in composites due to their material properties, heterogeneous nature, and layup configuration. Adhesive bonding allows flexibility in materials selection and offers improved production efficiency from product design and manufacture to final assembly, enabling cost reduction. However, the performance of adhesively bonded composite structures cannot be fully verified by inspection and testing due to the unforeseen nature of defects and manufacturing uncertainties presented in this joining method. These uncertainties can manifest as kissing bonds, porosity and voids in the adhesive. As a result, the use of adhesively bonded joints is often constrained by conservative certification requirements, limiting the potential of composite materials in weight reduction, cost-saving, and performance. There is a need to identify these uncertainties and understand their effect when designing these adhesively bonded joints. This article aims to report and categorise these uncertainties, offering the reader a reliable and inclusive source to conduct further research, such as the development of probabilistic reliability-based design optimisation, sensitivity analysis, defect detection methods and process development

A multi-technique and multi-scale analysis of the thermal degradation of PEEK in laser heating

Data availability: Data will be made available on request.Copyright © 2023 The Author(s). The present work studies the thermal degradation of laser-heated poly-ether-ether-ketone (PEEK) as the heating duration increases. Its damage morphology, chemical composition, crystallinity content, and mechanical properties are examined with optical microscopy, attenuated total reflection-Fourier transform infrared spectroscopy, differential scanning calorimetry, Raman spectroscopy, and continuous stiffness measurement nanoindentation. The applicability of those methods in detecting the thermal degradation of laser-heated PEEK and assessing the induced thermal damage is highlighted. Results show that short-time laser heating acts as an annealing process that improves the crystallinity and hardness on the affected surface of PEEK by up to 5.1% and 10.8% respectively. With a further increase in the heating duration, surface carbonisation occurs and a char layer is formed. Surface carbonisation is associated with the thermal limits of PEEK in laser heating decreasing by up to 50% its hardness and by 45% its indentation modulus. Finally, the char layer is found to act as a shielding mechanism that protects the bulk PEEK from the applied thermal load, resulting in mostly superficial thermally induced damage.This publication was made possible by the sponsorship and support of TWI. The work was enabled through, and undertaken at, the National Structural Integrity Research Centre (NSIRC), a postgraduate engineering facility for industry-led research into structural integrity established and managed by TWI through a network of both national and international Universities. Dimitrios Gaitanelis and Dr Angeliki Chanteli would like to thank Young European Research Universities Network (YERUN) for being awarded the YERUN Research Mobility Award 2021 to proceed to this collaboration. Dr Angeliki Chanteli and Professor Paul M. Weaver would like to thank Science Foundation Ireland (SFI) for funding Spatially and Temporally VARIable COMPosite Structures (VARICOMP) Grant No. (15/RP/2773) under its Research Professor programme

Online flow monitoring system development for the resin transfer moulding process

This work is the initial stage of the development of an online flow monitoring system for the resin impregnation phase of the Resin Transfer Moulding process. Online monitoring of the process is proposed to provide an estimation of the component’s state and to predict the defects, such as voids and dry spots. This paper analyses a dielectric sensor, which integrates to the process and measures the change in the impedance. The main contribution to the changes in the sensor response comes from the resin arrival on to the sensor during the impregnation phase. The proposed sensor consists of two parallel line electrodes embedded in an insulator. The design optimization is performed by analysing and modelling the geometry and the materials of the sensor. In addition, the developed monitoring system involves pressure transducers which measure the composite material state during the infusion phase. The pressure sensors operate as indicators of resin’s state and they are used for the process monitoring. This information will be used for the development of an algorithm for the resin frontal flow and enhance the insight of the flow defects mechanism.EPSRC CDTEI grant EP/L014998/1; European Union’s Horizon 2020 research and innovation programme (Clean Sky 2 Joint Undertaking, grant 686493)

The Effect of Changes in Magnetic Field and Frequency on the Vibration of a Thin Magnetostrictive Patch as a Tool for Generating Guided Ultrasonic Waves

Copyright: © 2022 by the authors. A set of experiments was designed and conducted to investigate the vibrational ultrasonic response of a thin magnetostrictive patch bonded to a glass plate, with changes in static and dynamic magnetic fields applied to the patch. Such arrangements are often used as a means of generating guided waves in pipes or plates, by attaching a patch to a sample’s surface. The effect of varying the applied static and dynamic magnetic field’s amplitudes and directions and the frequency of the dynamic magnetic field was studied. It was demonstrated that the vibration of the magnetostrictive patch could be controlled and enhanced by optimizing the magnetic fields. It was also shown that for low-amplitude dynamic magnetic fields, Lorentz forces generated within the patch and the resonant frequency of the patch could also contribute to the enhancement of the vibration of the patch for low-amplitude fields. For high-amplitude dynamic magnetic fields, the magnetostriction effect can be the main transduction mechanism, which can be optimized for non-destructive testing and inspection purposes.“NDTonAIR” Marie Skłodowska Curie Training Network in Non-Destructive Testing and Structural Health Monitoring of Aircraft structures (MSCAITN) under the action H2020-MSCA-ITN-2016- under Grant number 722134

Electrical and Mechanical Behaviour of Copper Tufted CFRP Composite Joints

Electrical continuity of dissimilar joints controls the current and thermal pathways during lightning strike. Tufting using carbon, glass or Kevlar fibres is a primary to introduce through thickness reinforcement for composite structures and assemblies. Replacing the conventional tuft thread material with metallic conductive wire presents an opportunity for enhancing current dissipation and deal with electrical bottlenecks across dissimilar joints. Simulation of the electro-thermo-mechanical behaviour of joints was carried out to assess the influence of metallic tufting. The finite element solver MSC.Marc was utilised. Mechanical models incorporate continuum damage mechanics (CDM) to capture progressive damage in both composite and aluminium components of the joint. The mechanical models were coupled with electrical and thermal simulations of reference and copper tufted carbon fibre epoxy composite joints to assess both the lightning strike response and mechanical robustness of the assembly as well as the improvements offered by tufting. Validation of the model is based on electrical conduction and temperature measurements alongside delamination tests.Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 887042, D-JOINTS

Design against distortion for aerospace-grade additively manufactured parts - PADICTON

Collections: Brunel Composite CentreAdditive manufacturing (AM) is a computer-controlled 3D printing process with increasing demand in the aerospace sector. This manufacturing process offers the production of lighter components, design flexibility, reduced labour effort and material cost, as well as decreased waste generation compared with subtractive manufacturing. Additionally, AM can provide parts availability at the point of use, significantly improving the supply chain. However, producing advanced high-temperature AM thermoplastic components remains a challenging task as these require a high-temperature build chamber environment that is prone to producing parts with thermal stresses and warpage. PADICTON project aims to develop a tool capable of accurately and rapidly predicting and correcting such distortions, offering improved quality of the produced parts and minimising rejection rates. Creating this tool requires conducting a comprehensive mechanical and thermal characterisation campaign to optimise the print parameters and part geometry. In this study, the concept of the project and the findings of the initial mechanical and optical characterisation tests for two AM processes, namely fused deposition modelling and selective laser sintering, are presented and discussed.The authors would like to acknowledge the PADICTON partners, namely FDM Digital Solutions, e Xstream Engineering, part of Hexagon Manufacturing Intelligence, AMendate, as well as the Topic Manager of the project, Airbus, for their assistance and encouragement towards the realisation of the activities. In addition, the consortium would like to express its gratitude to EOS for their technical support. Furthermore, the activities of PADICTON project have received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement number 86481

Electrical and mechanical behaviour of copper tufted CFRP composite joints

Electrical continuity of dissimilar joints controls the current and thermal pathways during lightning strike. Tufting using carbon, glass or Kevlar fibres is a primary to introduce through thickness reinforcement for composite structures and assemblies. Replacing the conventional tuft thread material with metallic conductive wire presents an opportunity for enhancing current dissipation and deal with electrical bottlenecks across dissimilar joints. Simulation of the electro-thermo-mechanical behaviour of joints was carried out to assess the influence of metallic tufting. The finite element solver MSC.Marc was utilised. Mechanical models incorporate continuum damage mechanics (CDM) to capture progressive damage in both composite and aluminium components of the joint. The mechanical models were coupled with electrical and thermal simulations of reference and copper tufted carbon fibre epoxy composite joints to assess both the lightning strike response and mechanical robustness of the assembly as well as the improvements offered by tufting. Validation of the model is based on electrical conduction and temperature measurements alongside delamination tests.European Union funding: 88704

Jig-less end-effector system for automating exhausting composite fuselage assembly tasks

Collections: Brunel Composite CentreIn this study, the jig-less end-effector system developed to assemble components of a full-scale multifunctional integrated composite thermoplastic lower fuselage section is tested and validated. To offset the environmental impact of higher volume of air transport, the aviation industry wants to design lighter and more environmentally friendly aircraft. To achieve this, there is a need to exploit novel materials and technologies. Advanced thermoplastic composites provide an excellent material option thanks to their weldability, low density, low overall production cost, improved fracture toughness and recyclability. However, to fully appreciate their capabilities and benefits, new manufacturing approaches and techniques are needed. Hence, projects such as TCTool, "innovative tooling, end-effector development and industrialisation for welding of thermoplastic components", aim to develop innovative tooling and end-effector systems for the assembly of a multifunctional thermoplastic fuselage. This study presents the development, operation, and testing of the jig-less end-effector system used in the TCTool project for picking, placing, and temporary welding and fixing fuselage's clips and stringers.This study has received funding from the Clean Sky 2 Joint Undertaking under the European Union's Horizon 2020 research and innovation program under grant agreement No. 865131 for TCTool Project, and has been partially funded by the projet “5R – Cervera Network in robotic technologies for intelligent manufacturing”, contract number CER-20211007, under “Centros Tecnológicos de Excelencia Cervera” (founded by “The Centre for the Development of Industrial Technology (CDTI)”). The authors would like to thank TWI Ltd. for conducting the tensile tests and optical microscopy. TCTool project partners: GKN-Fokker Aerospace, TWI Ltd., Andalusian Foundation for Aerospace Development – Advanced Center for Aerospace Technologies, Brunel University London, London South Bank University, Acroflight Ltd

Graphene-based strain sensing in composites for structural and health monitoring applications

Copyright © 2022 The Author(s). Composite structures are attracting more interest due to their outstanding mechanical properties; thus, their inspection and health assessment are key items for their safe use. In this article we present a graphene-based sensor that evaluates the strain generated within a composite. A finite element model was developed to investigate the mechanism driving the graphene to act as a strain sensor. A prototype sensor was manufactured, using a commercially available graphene ink. The strain in composite samples was measured and the gauge factor identified by applying different load scenarios. The graphene sensor proved to be able to evaluate strain at various levels providing a gauge factor (exceeding 6) higher than commercially available strain gauges.Innovate UK for the project GRAPHOSITE “A Graphene Sensor for Defect Detection and Predictive Maintenance in Composite Materials” [grant number 104266]