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Innovative thin-walled structures, bio-inspired by the microstructure of Morpho wings, were proposed as energy absorbing devices in this study. A finite element model, experimentally validated, was...

Cobalt ferrite as a magnetostrictive material has recently become of interest to many researchers due to its promising magnetostrictive properties. It has been proposed to be a suitable magnetostrictive material for some applications in the area of sensors and actuators. In such applications, speed of response with accurate displacements is important. Although cobalt ferrite has shown a small magnetostrictive coefficient, which is a disadvantage, it has also shown a very small hysteresis characteristic. It follows that the results of using this material should lead to a smaller amount of energy loss and higher displacement accuracy at high frequencies, and these benefits may outweigh this disadvantage. The aim of the study presented in this chapter is to introduce cobalt ferrite nanoparticles as the first step in a solution to improve the magnetostrictive coefficient of cobalt ferrite, if the particles are small enough to have only one magnetic domain.

To meet the increasing energy demand, renewable energy is considered the best option. Its patronage is being encouraged by both the research and industrial community. The main driving force for most renewable systems is solar energy. It is abundant and pollutant free compared to fossil products. Wind energy is also considered an abundant medium of energy generation and often goes hand in hand with solar energy. The last few decades have seen a sudden surge in wind energy compared to solar energy due to most wind energy systems being cost effective compared to solar energy. Wind turbines are often categorised as large or small depending on their application and energy generation output. Sustainable materials for construction of different parts of wind turbines are being encouraged to lower the cost of the system. The turbine blades and generators perform crucial roles in the overall operation of the turbines; hence, their material composition is very critical. Today, most turbine blades are made up of natural fiber-reinforced polymer (NFRP) as well as glass fiber-reinforced polymer (GFRP). Others are also made from wood and some metallic materials. Each of the materials introduced has specific characteristics that affect the system’s efficiency. This investigation explores the influence of these materials on turbine efficiency. Observations have shown that composites reinforced with nanomaterials have excellent mechanical characteristics. Carbon nanotubes have unique characteristics that may make them valuable in wind turbine blades in the future. It is possible to strengthen carbon nanotubes with various kinds of resins to get a variety of different characteristics. Similarly, the end-of-life treatment methods for composite materials is also presented.

Implant infection is a serious complication resulting in pain, mortality, prolonged recovery, and antimicrobial resistance (AMR). Reducing the risk-of-infection associated with tissue implants require imminent attention, where pure silver (Ag) offers enormous potential. However, the printability, mechanical performance nor microbial resistance of additively manufactured (AM) pure Ag is unavailable in literature. This is critical as Ag is thought to play a vital role in the development of AM patient-specific infection resistant implants in the decade to come. The study therefore additively manufactured 99.9% pure-Ag through selective laser melting (SLM) and systematically investigates its mechanical performance. The validated SLM process parameters were then used to conceive two fully porous bone scaffold each at approximately 68 and 90% (wt.) porosity. While the study brings to attention the potential defects in SLM pure-Ag through X-ray nanotomography (X-ray nCT), the mechanical properties of porous Ag scaffolds were found to be similar to cancellous bone. The study achieved the highest SLM pure-Ag density of 97% with Young’s modulus (E), elastic limit ( σ e ), yield strength ( σ y ), ultimate strength ( σ u l t ) and ultimate strain ( e u l t ) in the range of 15.5–17.8 GPa, 50.7–57.7 MPa, 57.6–67.2 MPa, 82.4–95.9 MPa and 0.07–0.10 respectively. The antimicrobial efficacy of printed silver was tested against the common implant infection-causing Staphylococcus aureus and led to 90% and 99.9% kill in 4 and 14 h respectively. The study, therefore, is a first step towards achieving a new generation Ag-based AM infection resistant porous implants.

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.

Metallic-based bipolar plates exhibit several advantages over graphite-based plates, including higher strength, lower manufacturing cost and better electrical conductivity. However, poor corrosion resistance and high interfacial contact resistance (ICR) are major challenges for metallic bipolar plates used in proton exchange membrane (PEM) fuel cells. Corrosion of metallic parts in PEM fuel cells not only increases the interfacial contact resistance but it can also decrease the proton conductivity of the Membrane Electrode Assembly (MEA), due to catalyst poisoning phenomena caused by corrosive products. In this paper, a composite coating of polytetrafluoroethylene (PTFE) was deposited on stainless steel alloys (SS304, SS316L) and Titanium (G-T2) via a CoBlast™ process. Corrosion resistance of the coated and uncoated metals in a simulated PEM fuel cell environment of 0.5 M H 2 SO 4 + 2 ppm HF at 70 °C was evaluated using potentiodynamic polarisation. ICR between the selected metals and carbon paper was measured and used as an indicator of surface conductivity. Scanning Electron Microscopy (SEM), 3D microscopy, Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and contact angle measurements were used to characterise the samples. The results showed that the PTFE coating improved the hydrophobicity and corrosion resistance but increased the ICR of the coated metals due to the unconductive nature of such coating. Thus, it was concluded that it is not fully feasible to use the PTFE alone for coating metals for fuel cell applications and a hybrid coating consisting of PTFE and a conductive material is needed to improve surface conductivity.

Functionally graded thickness (FGT) is an innovative concept to create light-weight structures with better material distribution and promising energy absorption characteristics suitable for vehicle crashworthiness applications. Accordingly, this paper suggests innovative circular tubes with in-plane thickness gradient along their perimeter and assesses their crashworthiness behaviour under lateral loading. Three different designs of circular tubes with thickness gradient were considered in which the locations of maximum and minimum thicknesses are varied. Selective laser melting method of additive manufacturing was used to manufacture the different tubes. Two different bulk powders including titanium (Ti6Al4V) and aluminium (AlSi10Mg) were used in the manufacturing process. Quasi-static crush experiments were conducted on the laser melted tubes to investigate their crushing and energy absorption behaviour. The energy absorption characteristics of the different FGT tubes were calculated and compared against a uniform thickness design. The results revealed that the best crashworthiness metrics were offered by FGT titanium tube in which the maximum thickness regions were along the horizontal and vertical directions while the minimum thickness regions were at an angle of 45° with respect to the loading direction. The aforementioned tube was found to absorb 79% greater energy per unit mass than its uniform thickness counterpart. Finally, with the aid of numerical simulations and surrogate modelling techniques, multi-objective optimisation and parametric analysis were conducted on the best FGT tube. The influences of the geometrical parameters on the crashworthiness responses of the best FGT structure were explored and the optimal thickness gradient parameters were determined. The results reported in this paper provide valuable guidance on the design of FGT energy absorption tubes for lateral deformation.

The reliability of solder joints is a critical issue in the microelectronics industry. The requirement of permanent electrical and thermal connections between solder alloys and the various components of a surface mount device is dependent upon the mechanical integrity of the solder and its interfaces. Accordingly, in this paper, the reliability of lead-free, Sn-3.8Ag-0.7Cu, and leaded, Sn-37Pb, solder alloys was investigated under both thermal-mechanical fatigue (TMF) and isothermal mechanical fatigue (IF) conditions. The investigation included material characterisation and fatigue testing on 4-ball grid array (BGA) specimens. The IF tests were carried out under load control at three different temperatures including Room Temperature (RT), 35 °C and 75 °C. Also, a set of ‘not-in-phase’ (nIP), ‘in-phase’ (IP) and ‘out-of-phase’ (OoP) combined thermal and mechanical cycling tests were carried out to investigate the TMF behaviour of the solders. The stress-life curves for each test condition were generated and then compared taking into account the observations on microstructure. It was found that the IF and TMF performance of Sn-3.8Ag-0.7Cu alloy was better than Sn-37Pb alloy when expressed as stress-life curves. Additionally, the Sn-3.8Ag-0.7Cu was less susceptible to the changes in temperature. This study provides a comprehensive insight into the reliability of solder alloys under a wide range of loading conditions.

Metallic foams are among the most promising class of materials due to their unique mechanical properties combining low mass with high stiffness, excellent energy absorption, and vibroacoustic damping. Consequently, noise control using methodically engineered metallic foams has received increased attention from both industrial and scientific community. Accordingly, this paper aims to present the mechanism of sound absorption along with the experimental and theoretical procedure that can be used to classify metallic foams. Additionally, the influence of design parameters on the resulting sound absorption coefficient of closed and open-cell metallic foams are explored. While Aluminium foams used to dominate the literature when it comes to acoustics, recent studies have reported Nickel-Inconel superalloy and Copper foams as having superior sound absorption coefficients.

Critically engineered stiffness and strength of a scaffold are crucial for managing maladapted stress concentration and reducing stress shielding. At the same time, suitable porosity and permeability are key to facilitate biological activities associated with bone growth and nutrient delivery. A systematic balance of all these parameters are required for the development of an effective bone scaffold. Traditionally, the approach has been to study each of these parameters in isolation without considering their interdependence to achieve specific properties at a certain porosity. The purpose of this study is to undertake a holistic investigation considering the stiffness, strength, permeability, and stress concentration of six scaffold architectures featuring a 68.46–90.98% porosity. With an initial target of a tibial host segment, the permeability was characterised using Computational Fluid Dynamics (CFD) in conjunction with Darcy's law. Following this, Ashby's criterion, experimental tests, and Finite Element Method (FEM) were employed to study the mechanical behaviour and their interdependencies under uniaxial compression. The FE model was validated and further extended to study the influence of stress concentration on both the stiffness and strength of the scaffolds. The results showed that the pore shape can influence permeability, stiffness, strength, and the stress concentration factor of Ti6Al4V bone scaffolds. Furthermore, the numerical results demonstrate the effect to which structural performance of highly porous scaffolds deviate, as a result of the Selective Laser Melting (SLM) process. In addition, the study demonstrates that stiffness and strength of bone scaffold at a targeted porosity is linked to the pore shape and the associated stress concentration allowing to exploit the design freedom associated with SLM.

This paper reports the design and development of a Proton Exchange Membrane (PEM) fuel cell using Aluminum 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. The fuel cell was then modelled and the findings are reported. The results obtained showed that using the open pore cellular foam material for the modelled fuel cell was more efficient compared to the traditional types of fuel cell in literature.

The aim of this work is to study the behavior of cobalt ferrite nanoparticles during sintering. The size of prepared nanoparticles was in the range between 5 and 25 nm. The density of nanoparticles was measured using a Pycnometer and found to be 4.93 g cc -1 . The nanoparticles were uniaxially pressed into disk samples, and sintered under a single, continuous, ramp rate. The maximum relative density of 96% was achieved when the sintering temperature was 1350 °C. This was considered 4% improvement in comparison with the density reported for cobalt ferrite prepared employing micro-particles. Pycnometer analysis on sintered disk samples determined the ratio of open and closed pores inside the sintered compacts.

In this paper, the sandwich tubes, which consist of thin-walled circular tubes with aluminium foam core, were proposed as energy absorption devices. The sandwich tubes were laterally crushed under quasi-static loading conditions. Detailed finite element model, validated against existing experimental results, was developed using the explicit code (ANSYS-LSDYNA) to assess the energy absorption responses and deformation modes. Response surface methodology (RSM) was employed in parallel with the finite element models to perform both parametric studies and multi-objective optimization in order to establish the optimal configuration of the sandwich tube. Sampling designs of the sandwich tubes were constructed based on a D - optimal design of experiment (DOE) method. Factorial analysis was performed using the DOE results to investigate the influences of the geometric parameters on the responses of sandwich tubes. In addition, multi-objective optimization design (MOD) of the sandwich tubes is carried out by adopting a desirability approach. It was found that the tube with a minimum diameter of the inner layer and a maximum foam thickness are more suitable for use as energy absorbing components. University of Aleppo

In this paper, sandwich tube components which consist of thin-walled circular tubes with aluminium foam core are proposed as energy absorption systems. The sandwich tubes were laterally crushed under quasi-static loading conditions. The sandwich tubes were crushed under two types of indenters and exposed to three different types of external constraints. The collapsing behaviour and the energy absorption responses of these systems were investigated by nonlinear finite element analysis through ANSYS-LS-DYNA. Various indicators which describe the effectiveness of energy absorbing systems were used as a marker to compare the various systems. It was found that the sandwich tube systems compressed by cylindrical indenters particularly the unconstrained system and the system with inclined constraints offered a very desirable force-deflection in which the force is almost constant in the post collapse stage. The employing of external constraints was noticed as a feasible method of increasing the SEA particularly when cylindrical indenter is used. Im Rahmen dieser Arbeit werden Kernverbundrohre, bestehend aus dunnwandigen Rohren mit Aluminiumschaumkern, als Energieabsorptionselemente vorgeschlagen. Die Kernverbundrohre wurden quasistatisch in lateraler Richtung zusammengedruckt. Die Kernverbundrohre wurden mittels zweier Arten von Eindringkopern under drei verschiedenen Auflagerbedingungen verformt. Das Versagensverhalten und das Energieabsorptionsverhalten wurden im Rahmen der nichtlinearen Finite-Elemente-Methode mittels ANSYS-LS-DYNA untersucht. Verschiedene Indikatoren, die die Effektivitat der Energieabsorptionssysteme beschreiben, wurden verwendet, um die unterschiedlichen Systeme zu vergleichen. Es hat sich gezeigt, dass die Kernverbundrohre mit zylindrischem Eindringkorper unter freier oder schrager Fuhrung ein vorteilhaftes Kraft-Verformungsverhalten aufweisen, wobei die Kraft weitgehend nach dem Versagen konstant bleibt. Die Verwendung von Verformungsbehinderungen und zylindrischer Eindringkorper stellte sich als eine Methode heraus, um das spezifische Energieabsorptionsvermogen zu erhohen.

Tubular systems are proposed to be used as energy absorber because they are cheap and easy to manufacture; recently some researchers use the elliptical tube as energy absorber. In this work, the influence of elliptical ratio (r =D1/D2) on energy absorption capability and load carrying capacity and stress of mild steel elliptical tubes has been investigated both experimentally and numerically, the experimental analyses conducted by using Zwick Type BT1-FB050TN testing instrument. This machine is universal instrument for performing tensile test and compression test, Fig (1) and bending test and it is consider as an important machine for measuring the mechanical properties of materials and structures. The loading frame consist of two vertical lead screws, a moving crosshead and an upper and lower bearing plate which bears the load of the lead screws. The maximum capacity of the loading frame attached to the table mounted unit is 50KN In this study a velocity between 310mm/min was applied to the moving component to ensure the quasistatic conditions whereas velocities between 0.5mm/min and 15 mm/min have been used by many researchers to simulate the quasi-static lateral compression of tubes between various indenters [1-2]. In addition to the experimental work, computational method using ANSYS is used to predict the loading and response of such tubes where series of models was performed with elliptical ratios ranging from 0.5 to 1.5. Comparison of numerical and experimental forcedeflection response is presented. It has been found that with changing the elliptical ratio of the tube the loaddeflection curve change and this leads to change the energy absorbed by tube, the changing of the geometrical shape of the tube leads to change the volume of this tube and hence the mass. By reducing the elliptical ratio to 0.5 the tube will absorb 43.3% more energy and the system will gain 102% more in terms of specific energy, fig (2).