CERES :: Browsing by Author "Webb, Phil"

Browsing by Author "Webb, Phil"

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Open Access
Adhesive joint geometry variation in non-rigid aircraft structures
(Cranfield University, 2019-11) Coladas Mato, Pablo; Webb, Phil; Xu, Yigeng
Adhesive bonding is a proven alternative to mechanical fasteners for structural assembly, offering lighter and thus more fuel efficient aircraft and cost-effective manufacturing processes. The effective application of bonded structural assemblies is however limited by the tight fit-up requirement, which is with tolerance ranges of hundreds of microns; this can be a challenge for the industry to meet considering the variability of current part manufacturing methods and the conservative nature of the conventional tolerance stack-up analysis method. Such a (perceived) limitation can discourage effective exploitation of bonding technologies, or lead to development of overengineered solutions for assurance. This work addresses such challenge by presenting an enhanced bondline thickness variation analysis accounting for part deflection of a bonded skinstringer assembly representing a typical non-rigid airframe structure. A semianalytical model accounting for unilateral contact and simplified 1D adhesive flow has been developed to predict bondline thickness variation of the assembly given the adherends’ mechanical properties, adhesive rheological properties, and external assembly forces or boundary conditions. A spectral-analysis method for assembly force requirement estimation has also been tested. The bondline dimensions of several representative test articles have been interrogated, including a reconfigurable test assembly designed specifically to test the input conditions that affect bondline geometry variation. It has been demonstrated that the part deflections need to be accounted for regarding the fit-up requirement of bonded non-rigid structural assembly. The semi-analytical model has been found to more reliable and realistic prediction of bondline thickness when compared to a rigid tolerance stack-up. The analysis method presented can be a major technology enabler for faster, more economical development of the aircraft of the future, as well as of any analogue structures with high aspect ratios where weight savings and fatigue performance may be core objectives.
Open Access
Advancements in 3D x-ray imaging: development and application of a twin robot system
(Brunel University, 2024-08-31) Asif, Seemal; Hryshchenko Sumina, Yuliya; Holden, Martin; Contino, Matteo; Adiuku, Ndidiamaka; Hughes, Bryn; Plastropoulos, Angelos; Avdelidis, Nico; Webb, Phil
development of a novel twin robot system for 3D X-ray imaging integrates advanced robotic control with mobile X-ray technology to significantly enhance diagnostic accuracy and efficiency in both medical and industrial applications. Key technical aspects, including innovative design specifications and system architecture, are discussed in detail. The twin robots operate in tandem, providing comprehensive imaging capabilities with high precision. This novel approach offers potential applications ranging from medical diagnostics to industrial inspections, significantly improving over traditional imaging methods. Preliminary results demonstrate the system's effectiveness in producing detailed 3D images, underscoring its potential for wide-ranging uses. Future research will focus on optimizing image quality and automating the imaging process to increase utility and efficiency. This development signifies a step forward in integrating robotics and imaging technology, promising enhanced outcomes in various fields.
Open Access
Communication components for Human Intention Prediction – a survey
(AHFE International, 2023-07-24) Khan, Fahad; Asif, Seemal; Webb, Phil
In this review we address the communication components for human intention prediction for Human-robot collaboration (HRC). The HRC is the approach in which human and robot(s) work towards achieving the same goal. The interaction can be both levels physical and cognitive. The traditional settings of the HRC system provides fixed robot program based on waypoints or gestures. It is difficult to predefine the instructions of the situation in complex and variable environment. The understanding of human intention on dynamic basis is crucial for the success of such systems. The core character of co-existence of human and the robot is to understand the dynamic scenes of human intentions. To understand the human intention there is need to understand the components of intention communication. This paper provides comprehensive overview about the understanding the intention as communication components and modelling those components by using machine learning technology in HRC. Multiple ways of communicating intention are possible by using speech, action, gesture, haptic, physiological signals, etc. The article details various approaches to understand the human intention communication aspect particularly in the Human Robot Collaboration setting.
Open Access
A cost-benefit forecasting framework for assessment of advanced manufacturing technology development
(Cranfield University, 2014-05) Jones, Mark Benjamin; Webb, Phil; Baguley, Paul
Development of new Advanced Manufacturing Technology (AMT) for the aerospace industry is critical to enhance the manufacture and assembly of aerospace products. These novel AMTs require high development cost, specialist resource capabilities, have long development periods, high technological risks and lengthy payback durations. This forms an industry reluctance to fund the initial AMT development stages, impacting on their success within an ever increasingly competitive environment. Selection of suitable AMTs for development is typically performed by managers who make little reference to estimating the non-recurring development effort in resources and hardware cost. In addition, the performance at the conceptual stage is predicted using expert opinion, consisting of subjective and inaccurate outputs. AMTs selected are then submerged into development research and heavily invested in, with incorrect selections having a detrimental impact on the business. A detailed study of the UK aerospace manufacturing industry corroborated these findings and revealed a requirement for a new process map to resolve the problem of managing AMT developments at the conceptual stages. This process map defined the final research protocol, forming the requirement for a Cost-Benefit Forecasting Framework. The framework improves the decision making process to select the most suitable AMTs for development, from concept to full scale demonstration. Cost is the first element and is capable of estimating the AMT development effort in person-hours and cost of hardware using two parametric cost models. Benefit is the second element and forecasts the AMT tangible and intangible performance. The framework plots these quantified cost-benefit parameters and is capable of presenting development value advice for a diverse range of AMTs with varied applications. A detailed case study is presented evaluating a total of 23 novel aerospace AMTs verifying the capability and high accuracy of the framework within a large aerospace manufacturing organisation. Further validation is provided by quantifying the responses from 10 AMT development experts, after utilising the methodology within an industrial setting. The results show that quantifying the cost-benefit parameters provides manufacturing research and technology with the ability to select AMTs that provide the best value to a business.
Open Access
The design and evaluation of an ergonomic contactless gesture control system for industrial robots
(Hindawi Publishing Corporation, 2018-05-14) Tang, Gilbert; Webb, Phil
In industrial human-robot collaboration, variability commonly exists in the operation environment and the components, which induces uncertainty and error that require frequent manual intervention for rectification. Conventional teach pendants can be physically demanding to use and require user training prior to operation. Thus, a more effective control interface is required. In this paper, the design and evaluation of a contactless gesture control system using Leap Motion is described. The design process involves the use of RULA human factor analysis tool. Separately, an exploratory usability test was conducted to compare three usability aspects between the developed gesture control system and an off-the-shelf conventional touchscreen teach pendant. This paper focuses on the user-centred design methodology of the gesture control system. The novelties of this research are the use of human factor analysis tools in the human-centred development process, as well as the gesture control design that enable users to control industrial robot’s motion by its joints and tool centre point position. The system has potential to use as an input device for industrial robot control in a human-robot collaboration scene. The developed gesture control system was targeting applications in system recovery and error correction in flexible manufacturing environment shared between humans and robots. The system allows operators to control an industrial robot without the requirement of significant training.
Open Access
Developed trigger mechanisms to improve crush force efficiency of aluminium tubes
(Elsevier, 2019-09-11) Rai, V.; Ghasemnejad, Hessam; Watson, James W.; Gonzalez-Domingo, J. A.; Webb, Phil
This paper aims to investigate the effect of a trigger mechanism on the crush force efficiency of aluminium tubular absorbers. Various trigger mechanisms such as cut-out holes, circumferential notch and end-fillet, were studied using the validated numerical model. Initially, tubes made of aluminium displayed better crashworthiness behaviour when compared with steel tubes based on numerical and experimental results. Then the trigger mechanism consisting of three cut-out holes was found more efficient than the ones with an end fillet and a circumferential notch based on a comparative study. According to these results, the developed trigger mechanisms have a significant change in crashworthiness performance of tubular absorbers. Crush force efficiency was doubled with the help of this trigger mechanism while stroke efficiency and specific energy absorptions were reduced by 4% and 15% respectively.
Open Access
The development and evaluation of Robot Light Skin: A novel robot signalling system to improve communication in industrial human–robot collaboration
(Elsevier, 2018-09-12) Tang, Gilbert; Webb, Phil; Thrower, John
In a human–robot collaborative production system, the robot could make request for interaction or notify the human operator if an uncertainty arises. Conventional industrial tower lights were designed for generic machine signalling purposes which may not be the ultimate solution for robot signalling in a collaborative setting. In this type of system, human operators could be monitoring multiple robots while carrying out a manual task so it is important to minimise the diversion of their attention. This paper presents a novel robot signalling solution, the Robot Light Skin (RLS),which is an integrated signalling system that could be used on most articulated robots. Our experiment was conducted to validate this concept in terms of its effect on improving operator's reaction time, hit-rate, awareness and task performance. The results showed that participants reacted faster to the RLS as well as achieved higher hit-rate. An eye tracker was used in the experiment which shows a reduction in diversion away from the manual task when using the RLS. Future study should explore the effect of the RLS concept on large-scale systems and multi-robot systems.
Open Access
Development of a CFRTP manufacturing method to improve low velocity impact resistance of aerospace structures.
(Cranfield University, 2020-08) Delporte, Yoan; Ghasemnejad, Hessam; Webb, Phil
A continuous carbon fiber reinforced Polymer was manufactured using a Fused Deposition Modelling method. Current Fused Deposition Modelling machine are not able to manufacture Carbon Fiber Reinforced Thermoplastic Polymer composite therefore modification and novel designs needed to be made and integrated to the Fused Deposition Modelling machine to achieve a final product. To investigate the benefits of our composite a comparison with available composites on the market composed of similar materials needed to be performed. We investigated the different aspect of the requirements needed to manufacture test samples. We focused on manufacturing method able to integrate continuous Carbon Fiber simultaneously to a thermoplastic. In the slicing software a custom g code sequence has been developed to forward the continuous Carbon Fiber through the Bowden tube to the hotend. This procedure allowed the hotend to move freely between the layup of the printed part. Also C code library has been developed to analyse the geometry of the part to recognise the amount of Carbon Fiber, which needs to be pushed through the Bowden tube connected to the hotend. We investigated the mechanical properties as well as the process parameters of the individual materials used to manufacture our Carbon Fiber Reinforced Thermoplastic Polymer samples. In addition Carbon Fiber Reinforced Thermoplastic low velocity impact samples have been produced to investigate the potential of our composite in comparison to available products on the marker like Short Carbon Fiber Polyamide filaments. The low velocity performances of the Continuous Carbon Fiber Thermoplastic Polymer samples have been promising compared to conventional Short Carbon Fiber Polyamide samples. The advantages of using an Fused Deposition Modelling machine to manufacture composites is the ease to choose between numerous fiber orientations, which a significantly important feature for impact applications. In addition a potential case study for aerospace structure applications of our Carbon Fiber Reinforced Thermoplastic Polymer will be investigated and discussed. The novelty behind this is research is in the coding sequence allowing the fiber cutting system to trigger a the a specific moment in order to integrate the necessary amount of fiber according to the distance of the hotend travelled on the heat bed. Another novelty is in the unique servo actuated fiber cutting system using a specific cutting mechanism. The contribution to the knowledge is the study of the behaviour of a thermoplastic composite under low velocity impact. To investigate the effect of process parameters on a thermoplastic composite. To develop a novel cutting system and code control. Vibration cancellation method for even and continuous integration of continuous carbon fiber cutting method for precise carbon fiber cutting and integration to thermoplastic via Bowden extrusion system. Coding for the motherboard firmware as well as G code for the slicer have been optimised in order to produce quality samples. The effect of hardware on process parameters have been investigated though tensile tests. Low velocity impact performance of continuous carbon fiber polyamide has been also investigated and tested.
Open Access
The development of a human-robot interface for industrial collaborative system
(Cranfield University, 2016-04) Tang, Gilbert; Webb, Phil
Industrial robots have been identified as one of the most effective solutions for optimising output and quality within many industries. However, there are a number of manufacturing applications involving complex tasks and inconstant components which prohibit the use of fully automated solutions in the foreseeable future. A breakthrough in robotic technologies and changes in safety legislations have supported the creation of robots that coexist and assist humans in industrial applications. It has been broadly recognised that human-robot collaborative systems would be a realistic solution as an advanced production system with wide range of applications and high economic impact. This type of system can utilise the best of both worlds, where the robot can perform simple tasks that require high repeatability while the human performs tasks that require judgement and dexterity of the human hands. Robots in such system will operate as “intelligent assistants”. In a collaborative working environment, robot and human share the same working area, and interact with each other. This level of interface will require effective ways of communication and collaboration to avoid unwanted conflicts. This project aims to create a user interface for industrial collaborative robot system through integration of current robotic technologies. The robotic system is designed for seamless collaboration with a human in close proximity. The system is capable to communicate with the human via the exchange of gestures, as well as visual signal which operators can observe and comprehend at a glance. The main objective of this PhD is to develop a Human-Robot Interface (HRI) for communication with an industrial collaborative robot during collaboration in proximity. The system is developed in conjunction with a small scale collaborative robot system which has been integrated using off-the-shelf components. The system should be capable of receiving input from the human user via an intuitive method as well as indicating its status to the user ii effectively. The HRI will be developed using a combination of hardware integrations and software developments. The software and the control framework were developed in a way that is applicable to other industrial robots in the future. The developed gesture command system is demonstrated on a heavy duty industrial robot.
Open Access
Do speed and proximity affect human-robot collaboration with an industrial robot arm?
(Springer, 2022-01-07) Story, Matthew; Webb, Phil; Fletcher, Sarah R.; Tang, Gilbert; Jaksic, Cyril; Carberry, Jon
Current guidelines for Human-Robot Collaboration (HRC) allow a person to be within the working area of an industrial robot arm whilst maintaining their physical safety. However, research into increasing automation and social robotics have shown that attributes in the robot, such as speed and proximity setting, can influence a person’s workload and trust. Despite this, studies into how an industrial robot arm’s attributes affect a person during HRC are limited and require further development. Therefore, a study was proposed to assess the impact of robot’s speed and proximity setting on a person’s workload and trust during an HRC task. Eighty-three participants from Cranfield University and the ASK Centre, BAE Systems Samlesbury, completed a task in collaboration with a UR5 industrial robot arm running at different speeds and proximity settings, workload and trust were measured after each run. Workload was found to be positively related to speed but not significantly related to proximity setting. Significant interaction was not found for trust with speed or proximity setting. This study showed that even when operating within current safety guidelines, an industrial robot can affect a person’s workload. The lack of significant interaction with trust was attributed to the robot’s relatively small size and high success rate, and therefore may have an influence in larger industrial robots. As workload and trust can have a significant impact on a person’s performance and satisfaction, it is key to understand this relationship early in the development and design of collaborative work cells to ensure safe and high productivity.
Open Access
Editorial for the special issue on manufacturing informatics for intelligent automation
(SAGE Publications (UK and US), 2017-01-01) Tiwari, Ashutosh; Webb, Phil; Prabhu, Vinayak Ashok
Open Access
A framework for flexible integration in robotics and its applications for calibration and error compensation
(Cranfield University, 2012-06) To, Minh Hoang; Webb, Phil
Robotics has been considered as a viable automation solution for the aerospace industry to address manufacturing cost. Many of the existing robot systems augmented with guidance from a large volume metrology system have proved to meet the high dimensional accuracy requirements in aero-structure assembly. However, they have been mainly deployed as costly and dedicated systems, which might not be ideal for aerospace manufacturing having low production rate and long cycle time. The work described in this thesis is to provide technical solutions to improve the flexibility and cost-efficiency of such metrology-integrated robot systems. To address the flexibility, a software framework that supports reconfigurable system integration is developed. The framework provides a design methodology to compose distributed software components which can be integrated dynamically at runtime. This provides the potential for the automation devices (robots, metrology, actuators etc.) controlled by these software components to be assembled on demand for various assembly applications. To reduce the cost of deployment, this thesis proposes a two-stage error compensation scheme for industrial robots that requires only intermittent metrology input, thus allowing for one expensive metrology system to be used by a number of robots. Robot calibration is employed in the first stage to reduce the majority of robot inaccuracy then the metrology will correct the residual errors. In this work, a new calibration model for serial robots having a parallelogram linkage is developed that takes into account both geometric errors and joint deflections induced by link masses and weight of the end-effectors. Experiments are conducted to evaluate the two pieces of work presented above. The proposed framework is adopted to create a distributed control system that implements calibration and error compensation for a large industrial robot having a parallelogram linkage. The control system is formed by hot-plugging the control applications of the robot and metrology used together. Experimental results show that the developed error model was able to improve the 3 positional accuracy of the loaded robot from several millimetres to less than one millimetre and reduce half of the time previously required to correct the errors by using only the metrology. The experiments also demonstrate the capability of sharing one metrology system to more than one robot.
Open Access
Human facial emotion recognition for adaptive human robot collaboration in manufacturing
(Brunel University, 2024-08-31) Khan, Fahad; Asif, Seemal; Webb, Phil
The integration of robots into various industries, including manufacturing, has introduced new challenges in achieving efficient human-robot collaboration. A crucial aspect of successful collaboration is the ability of robots to understand and respond to human emotions. In the context of human-robot collaboration in manufacturing, accurately predicting human emotions is essential for enhancing efficiency and safety. This paper presents a setup for human emotion detection, focusing on facial emotion recognition. The proposed model and descriptive summary involve the utilising state-of-the-art algorithms such as AlexNet, HaarCascade (HCC), MTCNN (Multi-Task Cascaded Convolutional Neural Networks), and SVM (Support Vector Machine), applied to datasets like CK+, JAFFE, and AffectNet. The performance of each facial recognition model is evaluated in real-time scenarios, resulting in significant progress with an accuracy improvement from 40% to 78.1%. These results demonstrate the effectiveness of the approach in enabling adaptive robot control based on human emotions and enhancing collaboration quality. This research uniquely integrates facial emotion recognition and robot control to enable adaptive responses during human-robot collaboration in manufacturing settings. By understanding and responding to human emotions, robots can improve their interactions with humans, leading to increased productivity and improved overall collaboration efficiency.
Open Access
Identification of the key design inputs for the FEM-based preliminary sizing and mass estimation of a civil aircraft wing box structure
(Elsevier, 2021-12-14) You, Chao; Yasaee, Mehdi; He, Shun; Yang, Daqing; Xu, Yigeng; Dayyani, Iman; Ghasemnejad, Hessam; Guo, Shijun; Webb, Phil; Jennings, James; Federico, Giovanni
FEM-based preliminary structural sizing has been successfully carried out for a typical single-aisle wing box structure using MSC Nastran, by considering various load cases representing typical aircraft manoeuvres, engine loads, landing and ground handling conditions. The strength, buckling and fatigue criteria have been applied as the design constraints for sizing. The resultant total mass and the structural (static and modal) behaviour of the sized wing box model have been verified against a validated high-fidelity wing box model. A sensitivity analysis has been performed to evaluate the influence of the number of design fields and the selected design inputs (i.e. load cases and design constraints) on the accuracy of sizing and mass estimation of the wing box. This sensitivity analysis has also been extended to the static and modal behaviour of the wing box structure obtained from sizing. It provides an insight into the significance of considering the buckling and fatigue constraints, aircraft rolling loads, engine loads and landing loads in sizing, in addition to the commonly-applied 2.5 g aircraft pull-up loads under the strength constraint. The findings of this study highlight the trade-off between the sizing efficiency and accuracy of a civil aircraft wing for modelling purposes.
Open Access
Managing delays for realtime error correction and compensation of an industrial robot in an open network
(MDPI, 2023-08-28) Asif, Seemal; Webb, Phil
The calibration of articulated arms presents a substantial challenge within the manufacturing domain, necessitating sophisticated calibration systems often reliant on the integration of costly metrology equipment for ensuring high precision. However, the logistical complexities and financial burden associated with deploying these devices across diverse systems hinder their widespread adoption. In response, Industry 4.0 emerges as a transformative paradigm by enabling the integration of manufacturing devices into networked environments, thereby providing access through cloud-based infrastructure. Nonetheless, this transition introduces a significant concern in the form of network-induced delays, which can significantly impact realtime calibration procedures. To address this pivotal challenge, the present study introduces an innovative framework that adeptly manages and mitigates network-induced delays. This framework leverages two key components: controller and optimiser, specifically the MPC (Model Predictive Controller) in conjunction with the Extended Kalman Filter (EKF), and a Predictor, characterised as the Dead Reckoning Model (DRM). Collectively, these methodologies are strategically integrated to address and ameliorate the temporal delays experienced during the calibration process. Significantly expanding upon antecedent investigations, the study transcends prior boundaries by implementing an advanced realtime error correction system across networked environments, with particular emphasis on the intricate management of delays originating from network traffic dynamics. The fundamental aim of this research extension is twofold: firstly, it aims to enhance realtime system performance on open networks, while concurrently achieving an impressive level of error correction precision at 0.02 mm. The employment of the proposed methodologies is anticipated to effectively surmount the intricacies and challenges associated with network-induced delays. Subsequently, this endeavour serves to catalyse accurate and efficient calibration procedures in the context of realtime manufacturing scenarios. This research significantly advances the landscape of error correction systems and lays a robust groundwork for the optimised utilisation of networked manufacturing devices within the dynamic realm of Industry 4.0 applications.
Open Access
Realtime calibration of an industrial robot
(MDPI, 2022-09-30) Asif, Seemal; Webb, Phil
In large scale, complex and low volume manufacturing systems, robotics are now considered unavoidable for automating the factory operations. The aerospace industry focuses on a high variety and quality but extremely low volume. The precision it requires for numerous tasks is unique and distinct from any other manufacturing industry. This can comprise accurate position, module assembly, inspection, fastening, etc. The scale of the robot invites different types of errors during operation, which can be either because of the kinematics of the robot or because of the environment (noise, temperature, load, etc.). There are packages available from robot manufacturers for the correction and compensation of errors on the robot to achieve accuracy. There are two associated problems: 1. cost and 2. static nature. They are very costly and they do not provide correction in realtime fashion (dynamic); the robot stops, waits for the correction, and then moves to the next position. The external tool to monitor the accuracy also requires attaching with the robot permanently. These are dedicated resources. These tools for accurate measurement are expensive and attached permanently to a robot, which means wastage of resources. These measuring tools are called metrology devices and attaching these devices and the robot to the network means that other robots/machines can also use these expensive tools for measurement. Our aim was to address two problems in this project: 1. calibration (error correction and compensation of robot) and 2. dynamic and realtime processing. It helped to perform the dynamic error correction and the compensation of an industrial robot. The results showed the error correction was achieved in the region of 0.02 mm.
Open Access
Robot Light Skin' paper data for Figures 5-11
(Cranfield University, 2018-11-08 11:38) chun gilbert Tang, Chi; Webb, Phil; Thrower, John
Experiment data used in the publication "The development and evaluation of Robot Light Skin: A novel robot signalling system to improve communication in industrial human–robot collaboration" for the concept validation of the Robot Light Skin (RLS), the data included correspond to the following figures in the publication: Reaction time to light signals fig 5, hit-rate fig 6, task performance fig 7, ease of monitoring fig 8, level of tiredness fig 9, and eye tracking fixation time fig 10 and 11.
Open Access
The simulation of automated leading edge assembly
(Cranfield University, 2015-09) Song, Qingming; Webb, Phil
Aircraft manufacturers are experiencing a fierce competition worldwide. Improving productivity, increasing throughput and reducing costs are influencing aircraft manufacturer’s future development. In order to improve competitiveness and provide sufficient and high quality products, it should reduce operations of aircraft assembly,majority of which are still in manual process, which limit production output. In contrast, these processes can be automated to replace manual operations. Much more attention should be placed on automated application. This project aims to propose a methodology to develop the automated assembly based on robotics and use this methodology to develop a new concept of Automated Leading Edge Assembly. The research selects an automated assembly process for further evaluation and brackets assembled on the front spar of Leading Edge are chosen to be automated assembly with robot assistant. The software DELMIA is used to develop and simulate the automated assembly process of brackets based on 3-D virtual aircraft Leading Edge models. The research development is mainly divided into three phases which are: (1) The state of art on Manual Leading Edge Assembly; (2) Automated Leading Edge Assembly framework development; (3) Automated Leading Edge Assembly framework evaluation including automated assembly process simulation based on DELMIA robotics workbench and automated assembly cost estimation. The research has proposed a methodology to develop the automated assembly based on robotics, proposed a new concept of Automated Leading Edge Assembly: using robots to replace workers to finish the assembly applications in the Leading Edge, and proposed a new automated bracket assembly process with laser ablation, adhesive bonding, drilling, riveting, and robot application. These applications can attract more and more engineers’ attention and provide preliminary knowledge for further study and detail research in the future.
Open Access
Structural mechanics of cylindrical fish-cell zero Poisson’s ratio metamaterials
(Elsevier, 2022-03-12) Qin, Qing; Dayyani, Iman; Webb, Phil
In this paper, a novel cylindrical metamaterial exhibiting zero Poisson’s ratio in two different directions is introduced. Detailed CAD modelling of a curved Fish-Cells necessary for numerical and experimental analysis are presented. High-fidelity finite element models are developed to assess the homogenisation studies of Poisson’s ratio, Young’s modulus and torsion behaviour, demonstrating the curvature effect and independency of the mechanical behaviour of cylindrical Fish-Cells metamaterial from tessellation numbers. Experimental analysis is performed to validate the zero Poisson’s ratio, deformation and fracture mechanism discussed in numerical simulations. Moreover, buckling and modal behaviours of the cylindrical Fish-Cells metamaterials are studied and compared with equivalent shell models.
Open Access
Transverse impact response analysis of graphene panels: Impact limits
(Scientific Research, 2019-04-08) Sonmez, Muhammed Burak; Ghasemnejad, Hessam; Kamran, Hammad; Webb, Phil
Explicit numerical studies were conducted to determine the transverse impact response of graphene panels. Although the mechanical properties of graphene are well documented in both quasi-static and dynamic conditions via nanoand microscopic studies, the impact behaviour of the material at the macroscale has not yet been studied and would provide interesting and crucial insight in to the performance of the material on a more widely recognizable scale. Firstly, a numerical impact model was validated against an analytical impact model based on continuum mechanics which showed good correlation between contact-force histories. The performance of graphene panels subjected to impact was compared to the performance of panels composed of aerospace-grade aluminium and carbon fiber reinforced polymer (CFRP) composite. The graphene panel was found to exhibit lower specific energy than aluminium and CFRP at the low-energy range due to its inherently superior stiffness and intrinsic strength. On the other hand, the ballistic limit of 3 mm thick graphene panels was found to be 3375 m/s, resulting in an impact resistance 100 times greater than for aluminium or CFRP, making graphene the most suitable material for high-velocity impact protection.

Browsing by Author "Webb, Phil"

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