On the crashworthiness performance of thin-walled energy absorbers: Recent advances and future developments

Over the past several decades, a noticeable amount of research efforts has been directed to minimising injuries and death to people inside a structure that is subjected to an impact loading. Thin-walled (TW) tubular components have been widely employed in energy absorbing structures to alleviate the detrimental effects of an impact loading during a collision event and thus enhance the crashworthiness performance of a structure. Comprehensive knowledge of the material properties and the structural behaviour of various TW components under various loading conditions is essential for designing an effective energy absorbing system. In this paper, based on a broad survey of the literature, a comprehensive overview of the recent developments in the area of crashworthiness performance of TW tubes is given with a special focus on the topics that emerged in the last ten years such as crashworthiness optimisation design and energy absorbing responses of unconventional TW components including multi-cells tubes, functionally graded thickness tubes and functionally graded foam filled tubes. Due to the huge number of studies that analysed and assessed the energy absorption behaviour of various TW components, this paper presents only a review of the crashworthiness behaviour of the components that can be used in vehicles structures including hollow and foam-filled TW tubes under lateral, axial, oblique and bending loading

Application of open pore cellular foam for air breathing PEM fuel cell

This is an accepted manuscript of an article published by Elsevier in International Journal of Hydrogen Energy on 07/06/2017, available online: https://doi.org/10.1016/j.ijhydene.2017.05.114 The accepted version of the publication may differ from the final published version.Open Pore Cellular Foam (OPCF) has received increased attention for use in Proton Exchange Membrane (PEM) fuel cells as a flow plate due to some advantages offered by the material, including better gas flow, lower pressure drop and low electrical resistance. In the present study, a novel design for an air-breathing PEM (ABPEM) fuel cell, which allows air convection from the surrounding atmosphere, using OPCF as a flow distributor has been developed. The developed fuel cell has been compared with one that uses a normal serpentine flow plate, demonstrating better performance. A comparative analysis of the performance of an ABPEM and pressurised air PEM (PAPEM) fuel cell is conducted and poor water management behaviour was observed for the ABPEM design. Thereafter, a PTFE coating has been applied to the OPCF with contact angle and electrochemical polarisation tests conducted to assess the capability of the coating to enhance the hydrophobicity and corrosion protection of metallic OPCF in the PEM fuel cell environment. The results showed that the ABPEM fuel cell with PTFE coated OPCF had a better performance than that with uncoated OPCF. Finally, OPCF was employed to build an ABPEM fuel cell stack where the performance, advantages and limitations of this stack are discussed in this paper

Acoustic behaviour of 3D printed titanium perforated panels

© 2021 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.rineng.2021.100252Titanium alloys such as Ti6Al4V is amongst the most widely studied metallic materials in the broad context of metal 3D printing. Although the mechanical performances are well understood, the acoustic performance of 3D printed Ti6Al4V, and Ti6Al4V ELI (Extra Low Interstitial) has received limited attention in the literature. As such, this study investigates the normal incidence sound absorption coefficient () and Sound Transmission Loss (STL) of both Ti6Al4V and Ti6Al4V ELI samples manufactured using Selective Laser Melting (SLM). The influence of material thickness on acoustic responses and the potential of developing Ti6Al4V micro-perforated panels (MPP) at 400–1600 Hz is also explored. The sound absorption of three aesthetic perforations printed using Ti6Al4V and the influence of a porous back layer was also investigated. The experimental measurements were carried out using an impedance tube following ISO10534-2. The result of the study establishes that 3D printed non-circular perforations featuring porous back-layer can exhibit improved sound absorption coefficient.This research was funded by the European Commission CALMERIC Grant 32R19P03053.Accepted versio

Sound pressure level of a Formula 3 car and the influence of detachable muffler-tip

© 2021 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.rineng.2021.100261This study presents the initial findings associated with the noise emission tests that were carried out in preparation of the UWR Formula 3 car. Even though Formula 3 (F3) race cars are excluded from road vehicle noise emission regulations (EU No. 540/2014), their emission is closely regulated by Fédération Internationale de l’Automobile (FIA) technical regulations. According to FIA regulations, the noise generated by participating cars must not exceed 110 dB (A-weighted) under specific test conditions. The acoustic tests presented in this study were carried out at RAF (Royal Air Force) Cosford airfield in the UK closely simulating FIA recommended conditions. The tests were established to characterise the noise emission of the car during drive-by and stationary conditions. In addition to measuring the Sound Pressure Level (SPL) emitted, the study was extended to evaluating the performance of a detachable muffler tip that is permitted under the FIA regulations. The study found that the tested muffler-tip did not reduce the LAeq acoustic emission under any of the test cases considered. Nevertheless, introducing muffler-tip worsened the LAeq levels by 0.2 dB which is within the standard acoustic measurement uncertainty. Overall, the paper establishes the noise levels associated with F3 cars and the requirement for customised muffler-tips as opposed to aftermarket ones for meaningful noise reduction without adversely affecting performance.Accepted versio

Design and development of proton exchange membrane fuel cell using open pore cellular foam as flow plate material

This paper reports the design and development of a Proton Exchange Membrane (PEM) fuel cell using open pore cellular metal foam as the flow plate material. Effective housing designs are proposed for both hydrogen and oxygen sides and through the application of Computational Fluid Dynamic (CFD) modelling and analysis techniques the flow regime through the open pore cellular metal foam flow plate are identified. Based on the CFD results the best anode housing design was selected and manufactured. The fuel cell was assembled and tested and the findings are reported

Comprehensive investigation on hydrogen and fuel cell technology in the aviation and aerospace sectors

The world energy consumption is greatly influenced by the aviation industry with a total energy consumption ranging between 2.5% and 5%. Currently, liquid fossil fuel, which releases various types of Greenhouse Gas (GHG) emissions, is the main fuel in the aviation industry. As the aviation industry grows rapidly to meet the requirements of the increased world population, the demand for environmentally friendly power technology for various applications in the aviation sector has been increased sharply in recent years. Among the various clean power sources, energy obtained from hydrogen is considered the future for energy generation in the aviation industry due to its cleanness and abundance. This paper aims to give an overview of the potential aviation applications where hydrogen and fuel cell technology can be used. Also, the major challenges that limit the wide adoption of hydrogen technology in aviation are highlighted and future research prospects are identified

Perforated steel stud to improve the acoustic insulation of drywall partitions

©2021 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/acoustics3040043Steel studs are an inevitable part of drywall construction as they are lightweight and offer the required structural stability. However, the studs act as sound bridges between the plasterboards, reducing the overall sound insulation of the wall. Overcoming this often calls for wider cavity walls and complex stud decoupling fixtures that increase the installation cost while reducing the floor area. As an alternative approach, this research reveals the potential of perforated studs to improve the acoustic insulation of drywall partitions. The acoustic and structural performance is characterized using a validated finite element model that acted as a prediction tool in reducing the number of physical tests required. The results established that an acoustic numerical model featuring fluid-structure-interaction can predict the weighted sound reduction index of a stud wall assembly at an accuracy of ±1 dB. The model was used to analyze six perforated stud designs and found them to outperform the sound insulation of non-perforated drywall partitions by reducing the sound bridging. Overall, the best performing perforated stud design was found to offer improvements in acoustic insulation of up to 4 dB, while being structurally compliant.Published onlin

Theoretical and numerical crush analysis of multi-stage nested aluminium alloy tubular structures under axial impact loading

In this paper, the crush behaviour and energy absorption performance of nested tubular thin-walled structures made of aluminium alloy AA6061-O under dynamic axial loading are investigated. Theoretical solutions for Average Crush Force () of these structures are proposed by combining the energy method, simple superposition principle, and interaction among the various components of the structures. The derived theoretical models are verified by comparing their predictions with numerical and experimental values. The energy absorption indicators of the various structures are calculated and used to compare the various structures and to determine the best performing one. It is found that the nested structure with a higher number of tubes exhibits the best crashworthiness performance due to energy absorption enhancements resulted from the interaction effects between its components as well as its capability to reduce the peak crush force

Crushing and energy absorption properties of additively manufactured concave thin-walled tubes

© 2022 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.rineng.2022.100424Developing an innovative protective structure with excellent energy absorption performance is a continuous research effort. The emerging additive manufacturing techniques allow fabricating structures with complex geometrical shapes which have the potential to yield unprecedented energy absorption properties. Accordingly, in this paper, the crush and energy absorption behaviour of new designs, namely Concave Tubes (CTs) featuring inwardly curved sidewalls, is assessed experimentally and compared to that of Standard tubes (STs) featuring straight sidewalls. Tubes with different geometrical configurations, including concave circular (CC), concave square (CS), standard circular (SC), and standard square (SS), are fabricated using the Selective Laser Melting (SLM) process from AlSi10Mg aluminium powder and then crushed axially under quasi-static loading. It was found that the tubes have fractured and developed a splitting deformation mode, instead of progressive buckling, during the axial crushing resulting in relatively low energy absorption performance. The experimental results revealed superior energy absorption performance for the CTs over the STs. A Multi-Attribute Decision Making (MADM) technique known as Complex Proportional Assessment (COPRAS) is used to identify the best design. The COPRAS results show that the CC design is the best energy absorbing tube outperforming all other configurations presented in this paper.Accepted versio

3D printed auxetic nasopharyngeal swabs for COVID-19 sample collection

This is an accepted manuscript of an article published by Elsevier in Journal of the Mechanical Behavior of Biomedical Materials on 12/11/2020, available online: https://doi.org/10.1016/j.jmbbm.2020.104175 The accepted version of the publication may differ from the final published version.The COVID-19 pandemic has resulted in worldwide shortages of nasopharyngeal swabs required for sample collection. While the shortages are becoming acute due to supply chain disruptions, the demand for testing has increased both as a prerequisite to lifting restrictions and in preparation for the second wave. One of the potential solutions to this crisis is the development of 3D printed nasopharyngeal swabs that behave like traditional swabs. However, the opportunity to digitally conceive and fabricate swabs allows for design improvements that can potentially reduce patient pain and discomfort. The study reports the progress that has been made on the development of auxetic nasopharyngeal swabs that can shrink under axial resistance. This allows the swab to navigate through the nasal cavity with significantly less stress on the surrounding tissues. This is achieved through systematically conceived negative Poisson's ratio (-ν) structures in a biocompatible material. Finite element (FE) and surrogate modelling techniques were employed to identify the most optimal swab shape that allows for the highest negative strain (-∊lat) under safe stress (σvon). The influence and interaction effects of the geometrical parameters on the swab's performance were also characterised. The research demonstrates a new viewpoint for the development of functional nasopharyngeal swabs that can be 3D printed to reduce patient discomfort. The methodology can be further exploited to address various challenges in biomedical devices and redistributed manufacturing.This research was conducted with support from the CALMERIC grant [European Commission, Grant number: 32R19P03053]; 6DME Ltd. UK; and Formlabs GmbH.Published versio