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This work deals with the development of an improved numerical model, based on the explicit finite element method, aimed at investigating the energy absorption capabilities of a full-scale composite...

Driven/driving shafts are the most important portion of rotating devices. Misdiagnosis or late diagnosis of these components could result in severe vibrations, defects in other parts (particularly bearings), and ultimately catastrophic failures. A shaft bow is a common problem in heavy rotating systems equipped with such attachments as blades, discs, etc. Many factors can cause the shaft bending; this malfunction can be temporary, such as the bow resulting from a rotor gravitational sag, or can be permanent, such as shrink fitting. Since bending effects are similar to those induced by the classic eccentricity of the mass from the geometric center, i.e., unbalancing, distinguishing the differences in dynamic behaviors, as well as the symptoms, can be a labor-intensive and specialized task. This article represents a review of almost all the investigations and studies that have been carried out on the diagnosing and balancing of bowed rotating systems. The articles are categorized into two major classes, diagnosing and balancing/correcting approaches to bowed rotors. The former is divided into three subclasses, i.e., time-domain, frequency-domain, and time–frequency-domain analyses; the latter is divided into three other sub-sections that concern influence coefficient, modal balancing, and optimization method in correcting. Since the number of investigations in the time domain is relatively high, this category is subdivided into two groups: manual and smart inspection. Finally, a summary is provided, as well as some new research prospects.

In the case of catastrophic events, such as an emergency landing, the fuselage structure is demanded to absorb most of the impact energy preserving, at the same time, a survivable space for the passengers. Moreover, the increasing trend of using composites in the aerospace field is pushing the investigation on the passive safety capabilities of such structures in order to get compliance with regulations and crashworthiness requirements. This paper deals with the development of a numerical model, based on the explicit finite element (FE) method, aimed to investigate the energy absorption capability of a full-scale 95% composite made fuselage section of a civil aircraft. A vertical drop test, performed at the Italian Aerospace Research Centre (CIRA), carried out from a height of 14 feet so to achieve a ground contact velocity of 30 feet/s in according to the FAR/CS 25, has been used to assess the prediction capabilities of the developed FE method, allowing verifying the response under dynamic load condition and the energy absorption capabilities of the designed structure. An established finite element model could be used to define the reliable crashworthiness design strategy to improve the survival chance of the passengers in events such as the investigated one.

Fiber-reinforced composite materials are increasingly present in areas such as automotive, aeronautics, defense, sport, used due to their special mechanical characteristics and very good behavior under heavy working conditions. New mold design techniques (such as 3D printing technologies), processing (such as the use of robotic technologies), open new opportunities for future challenges. This paper represents research on analysis techniques for the design of composite materials products made of fiber-reinforced, research on the use of devices with feedback loop for mechanical cutting technologies, which allow intelligent dynamic adjustment of the processing regimes, analysis of manufacturing technologies used as unconventional processes for the implementation of inclusion components, economic judgments on advantages, disadvantages of the techniques and methods used.

The demand for conductive fuel cell stack components contributed to the research and development of composite materials and technologies. Significant activities were directed to the study of low-cost bipolar plates made in thermosets and thermoplastics manufactured by compression and injection molding. For the production of conductive thermoplastics carbon-polymers composites are used methods including thermokineting, twin screw extruder, or Banbury type mixing. In this paper are presented the results of research of a technology combining the mixing of the pellets of a composite carbon black in a polymer matrix with expanded graphite and conveying the compound to the injection molding unit and then, the melt injection molded into a micro-channel bipolar plate for a proton exchange membrane fuel cell (PEMFC).

In a bolted joint, the preload level resulting from the tightening torque represents a very important parameter governing the stresses distributions involving the joint under the real loading conditions. This paper deals with the development of a Finite Element (FE) model for the investigation of the effects of some selected preload levels on the stress-strain states affecting both bolt and plate in a single lap joint. The aim of this FE model is to support the design phase of strain gauges instrumented bolt to evaluate experimentally the rate of tensile load applied to the joint that the bolt absorbs with different preloads. The test article consists of two steel plates, a steel bolt and an aluminum nut. The results herein presented showed firstly that, without bolt preload, the tensile load applied to the joint is completely transferred to the bolt and that the load transferred to the bolt almost linearly decreases as the preload increases. Moreover, at a selected preload level, the transversal and longitudinal stresses (with respect to the load direction) increase as the tensile load increases, while the stress along the plate thickness direction decreases, reaching negative values. On the other hand, at a selected tensile load level, the transversal and longitudinal stresses as well as the stress along the thickness direction decrease as the preload level increases. Predicting the mechanical behaviour of the only bolted joint, if the same bolt model will be used to simulate the mechanical behaviour in a hybrid single-lap joint, possible imperfections of the model will have to certainly be linked to the modelling of the adhesive.

In near future, the main challenge is to reduce the use of fossil fuels that currently emit the bulk of global CO2 emissions, responsible of the global warming and climate change. Hydrogen, as a future fuel candidate, would play a significant role for net-zero emission requirements. As a matter of fact, new hydrogen tank design is needed to bring this technology to the readiness level. This paper aims to investigate on the impact resistance of a hybrid aluminum-composite hydrogen tank. In particular, the paper presents the development of two finite element (FE) models for the simulation of two impact scenarios experimentally investigated and proposed in literature. The models provided acceptable levels of accuracy with consequent benefits in supporting designers in the certification process of such device type.

This paper deals with the development of a finite element (FE) model for the simulation of a bird strike event on an innovative leading edge made of ARALL (ARamid ALuminum Laminate) material. To assess the reliability of the FE analyses, a preliminary model is developed aiming to simulate a tensile test, according to literature, involving ARALL specimens. Such model provides a good level of accuracy. So, the same modeling technique has been used for the bird strike simulation. Finally, the structural response of the ARALL leading edge has been compared against a conventional Aluminum one. Such a comparison has highlighted the capability of ARALL material in withstanding bird strike events with an improved performance.

The aim of this study is to investigate the mechanical properties of the specimens made of Ti6Al4V titanium alloy with EBM additive technology. Tensile tests on the component are carried out on “dog bone” specimens, of fixed dimensions, printed with orientations of 0°, 45°, and 90°. The results of the experimental campaign confirm the influence printing parameters of the technology on the mechanical performance of the components. Subsequently, the numerical-structural analysis carried out on the Octet-Truss elementary cell in Ti6Al4V titanium alloy shows that the mechanical behavior of the cell is influenced by the material growth orientation and confirmed that the orientation of 45° guarantees cells more resistant to loads of traction, while the orientations of 0° and 90° make up more deformable cells. The investigation of the mechanical properties of the components involved specimens with a solid material configuration and specimens is emptied by means of reticular structures. The results of the survey are compared with the same volume and with the same analysis. Direct observation of the stress–strain curves reveals a difference in the value of the elastic modulus, resulting in a linear section of the curve that is less steep in the case of the assembled component. The choice of the printing parameters is a crucial point in the construction process of the components made in Additive Manufacturing since, as confirmed by this study, the parameters of the technology influence the properties of the material and therefore of the printed component. Secondly, exploiting the potential of additive technologies in creating structures with complex geometry (such as lattice structures), offers the possibility, not only to reduce the weight of the components, but also to improve the final performance.

In the polymer products industry, new technologies and Industry 4.0 concepts represent real solutions to increase efficiency and profitability through creating the intelligent and adaptable manufacturing system. At the same time, the existing manufacturing systems have made sustained efforts to implement Lean principles, techniques and tools to achieve process efficiency by eliminating waste and continuously improving performance. The production system architecture consists of active production resources, which participate directly in the production process flow, and passive elements, which have a supporting role. In Industry 4.0, these elements form a dynamic cyber-physical production subsystem, through which different manufacturing solutions can be managed. Updating Lean production systems to Industry 4.0 level is obtained by implementing Lean tools and principles to the cyber-physical system. This work presents the results of research on transforming a Lean instrument a into a Lean 4.0 solution, applicable to manufacturing cells processes, in an Industry 4.0 manufacturing system.

The fulfilment of the crash is a demanding requirement for a Tiltrotor. Indeed, such a kind of aircraft, being a hybrid between an airplane and a helicopter, inherits the requirements mainly from helicopters (EASA CS 29) due to its hovering ability. In particular, the fuel storage system must be designed in such a manner that it is crash resistant, under prescribed airworthiness requirements, in order to avoid the fuel leakage during such an event, preventing fire and, thus, increasing the survival chances of the crew and the passengers. The present work deals with the evaluation of crashworthiness of the fuel storage system of a Tiltrotor (bladder tank), and, in particular, it aims at describing the adopted numerical approach and some specific results. Crash resistance requirements are considered from the earliest design stages, and for this reason they are mainly addressed from a numerical point of view and by simulations that treat both single components and small/medium size assemblies. The developed numerical models include all the main parts needed for simulating the structural behavior of the investigated wing section: the tank, the structural components of the wing, the fuel sub-systems (fuel lines, probes, etc.) and the fuel itself. During the crash event there are several parts inside the tanks that can come into contact with the tank structure, therefore, it is necessary to evaluate which of these parts can be a damage source for the tank itself and could generate fuel loss. The SPH approach has been adopted to discretise fuel and to estimate the interaction forces with respect to the tank structure. Experimental data were used to calibrate the fuel tank and foam material models and to define the acceleration time-history to be applied. Thanks to the optimized foam’s configuration, the amount of dissipated impact energy is remarkable, and the evaluation of tanks/fuel system stress distribution allows estimating any undesired failure due to a survivable crash event.

In the last years, a significant interest has been pointed out in the capability of ultrasonic guided waves as candidate tool for structural health monitoring (SHM), due to their high damage detection sensitivity and low power consumption. The monitoring of the structural health through the propagation of guided waves is complex: some wave phenomena, namely dispersion and slowness, together with boundary scattered waves, may mask the presence of damages. So, studying the dispersion phenomenon through the dispersion curves may be helpful in understanding the propagation mechanisms. As Lamb waves dispersion equations do not generally have analytical solutions, the development of a predictive finite element (FE) model can be a valuable tool for the improvement of SHM systems, avoiding the high cost of experimental campaigns. Thus, once calibrated with respect to an experimental test case, the developed FE model can be used to simulate and predict guided-wave propagation mechanisms in a given structure. This leads to the possibility of employing such approach to identify and localize potential structural damages, that is the final aim of an SHM system. In this work, the FE method, together with an in-house code, has been used to investigate guided wave dispersion phenomenon in plates for possible SHM applications.

Composite materials are increasingly used in those fields where it is necessary to achieve the requirements of lightweight and high mechanical properties. Even though their high specific strength which get these materials very attractive, especially for the transport field, there are several critical issues that still limit their application in primary structures. Among these, dynamic loading conditions play a critical role because they can significantly lower their residual strength. This paper aims to investigate experimentally the structural response of a 25 mm thick Omega composite structure under different impact loading conditions. The investigated test article consists of E-glass fibres (40% volume fraction) reinforced polyester matrix. The structure is covered by a HELIOPOL 1401 M AGC W 11 gelcoat layer and it has been impacted through a drop mass of 3.94 kg, dropped from heights of 50 mm, 75 mm, 100 mm, 150 mm, 200 mm, 250 mm, 350 mm and 500 mm.

This paper deals with technological solutions of innovative engine encapsulation systems for automotive. The aim of this device is to insulate acoustically and thermally the engine from the environment, in order to keep its temperature higher for more hours after it has been switched off. If the engine is subsequently started within this interval, the higher temperature involving the lubricating oil will allow reducing its viscosity, resulting in a lower level of energy dissipation due to friction losses, a lower fuel consumption and, consequently, a lower CO2 emission level. In this paper, a finite element model is carried out in order to investigate on the thermo-mechanical behavior of the proposed engine encapsulation system.

In the present work, a preliminary design of an eco-sustainable bamboo electric treadmill bike is carried out. It is a new means of transport with zero environmental impact that also allows to overcome the main disadvantage of the indoor training. Bamboo, as an eco-friendly material, has great potential as construction material for bike frames because it represents an alternative for more traditional materials such as steel, aluminum, and composite. A finite element model of the designed prototype is developed and then validated using Abaqus commercial code following the UNI EN 14764 static standard. Numerical analyses show good structural behavior of the designed frame in compliance with the regulations.

As well-known, experimental drop tests for the study of the passive safety of aeronautical structures are very expensive and, therefore, in many cases complex to be replicated. In this context, the support of already-validated numerical tools is fundamental to reduce costs, develop new structural solutions and carry out further tests with the awareness to have got underlying reliable numerical results. This article deals with the development of a finite element model of a fuselage section suitable for usage in structural optimizations and designs of experiment with crashworthiness purposes. FE model has been made starting from a more complex numerical model used previously by authors to replicate accurately an experimental drop test. Several simplifications have been performed allowing reducing sharply the computational costs. After an overview of both models, paper is addressed to show the reliability of the simplified FE model, against the complex one, by comparing the internal energy and the deformations predicted by both models. The simplified model was found to be a suitable tool in terms of level of accuracy and computational costs.

The improvement of the current design practice, especially for conventional materials, has allowed the production of structures able to better tolerate the presence of cracks and, in general, damages under the in-service loading conditions. As a result, especially in the aerospace field, nowadays, the damage tolerance philosophy is the core of the current design practice. However, conversely to the conventional materials, composite materials still cannot count on established prediction models supporting the damage tolerance approach. Among the critical damages which could affect composite materials, BVIDs (Barely Visible Impact Damages) due to accidental Low Velocity Impact (LVI) phenomena play a critical role. Since they cannot be easily detectable during the inspection intervals, in order to fulfil the damage tolerance targets, large safety factors are applied during the design current practice, resulting in the oversizing of the structure. For these reasons, Structural Health Monitoring (SHM) techniques are being widely used for the improvement of the current design practice, allowing the damage detection. Thanks to the possibility to assess the structural health during the in-service loading conditions, Lamb waves, among the several non-destructive testing (NDT), appear to be the best candidate for damage detection. Studies on this topic are never enough and the literature cannot still count on a Finite Element (FE) procedure able to simulate Lamb wave propagation on LVI damaged plates. This work deals with a FE procedure, developed by using the FE code Abaqus v.6.14®, for the simulation of the interaction between ultrasonic guided waves and LVI damages in composite laminates, whose damages have been modelled by means of Hashin criteria in a previous impact simulation.

The aim of this work is to propose a numerical methodology based on the finite element (FE) method to investigate the dispersive behavior of guided waves transmitted, converted, and reflected by reinforced aluminum and composite structures, highlighting their differences. The dispersion curves of such modes can help designers in improving the damage detection sensitivity of Lamb wave based structural health monitoring (SHM) systems. A preliminary phase has been carried out to assess the reliability of the modelling technique. The accuracy of the results has been demonstrated for aluminum and composite flat panels by comparing them against experimental tests and semi-analytical data, respectively. Since the good agreement, the FE method has been used to analyze the phenomena of dispersion, scattering, and mode conversion in aluminum and composite panels characterized by a structural discontinuity, as a stiffener. The research activity allowed emphasizing modes conversion at the stiffener, offering new observations with respect to state of the art. Converted modes propagate with a slightly slower speed than the incident ones. Reflected waves, instead, have been found to travel with the same velocity of the incident ones. Moreover, waves reflected in the composite stiffened plate appeared different from those that occurred in the aluminum one for the aspects herein discussed.

The paper deals with dynamic tensile tests on Carbon Fibre Reinforced Polymer – CFRP laminates. As a result of their viscoelastic nature, plastics exhibit rate dependence in their stress-strain response. The need to develop failure criteria to determine the dynamic failure stress for composite material under dynamic loading conditions is a current challenge for the research community. The main goal of such paper is to assess the efficiency of the analytical models provided by literature to predict the strain-rate effects on composite coupons tensile strength. Moreover, experimental tests have been performed in order to evaluate the mechanical behaviour of different stacking sequences at different strain rate.

In the aircraft industry, crashworthiness design and certification phases have been and are going to be the most attractive topics for designers, mostly because of the increasing use of composites for primary structural components. It is well known that the cargo subfloor elements of the fuselage structure play a crucial role in absorbing the kinetic energy during a crash. In particular, the stanchions, or struts, are important parts for the structural response; as a matter of fact, they connect the fuselage frames to the cabin’s floor and, ideally, are expected to crush under a compressive force in order to dissipate the impact energy in a controlled way and, consequently, to minimize the energy transferred to the passengers. The aim of this work is to demonstrate, experimentally and numerically, the energy absorption capability of the stanchions, made of both composite material and aluminium alloy, of a full-scale 95% composites made fuselage section under a critical load condition, such as an emergency landing. A Finite Element model allowing estimating the passive safety capabilities of the designed struts has been developed and herein proposed.

Laminated composite plates are widely used in the aerospace field, the prediction of their residual life is a interesting challenge for research communities. Their structural behaviour could be affected by several rupture mechanisms due to exercise loading conditions. One of the most critical is the low velocities impacts with different impact energies. This paper deals with an experimental test program performed in order to validate a numerical model developed by using finite element method. All experimental tests were carried out under international standard ASTM D7136 while all numerical tests were carried out by use of a worldwide numerical code Abaqus®. Inter-laminar and intra-laminar rupture mechanisms were taken into account and special-purpose elements were used. Rupture criteria were implemented in the numerical models thanks to their functional ease; results of numerical-experimental comparison were presented and discussed.

During recent years, industrial world faced transformations that led companies to introduce the concepts and the technologies of a new industrial paradigm, named Industry 4.0 (I4.0), in order to improve their products and their production processes. In the context of I4.0, factories are becoming smart, more flexible and collaborative, satisfying the current demands of increasingly competitive markets and of products closer to the real needs of customers. Within this framework, the approach to product and process design is changing too, supported by the use of complex numerical analyses for testing and validating the performance of both products and production processes. This is made possible thanks to the Digital Manufacturing (DM) approach, that allows to reduce the design times and to validate the design solution in virtual environments, without setting up detailed and expensive experimental sessions. This paper aims to propose a possible methodological framework to better carry out the design of new products and production systems, according to the DM principles.

Hybrid mechanical joints are achieved by the simultaneous use of multiple connection mechanisms such as bolting and bonding. This technique allows to obtain advantages in terms of mechanical properties compared to simple joints such as longer fatigue life and operability in critical environmental conditions. Many parameters influence the structural behavior of the hybrid junctions in this perspective numerical simulation can play a decisive role to the cause. Using hybrid joints allows generally to obtain a more homogeneous stress distribution than bolted ones which is why, over the years, such type of joint is widely used in the automotive and naval industries as well as in the avionics, with particular reference to the residual strength in partially damaged components. In the present work, a numerical model representative of tensile tests on single lap joints characterized by adherends of different nature is presented.

Most mechanical structures are composed of several components of different shape, size and material. In order to guarantee the connections among such parts is often necessary to adopt different connection mechanisms. The joints represent the structure possible weak points, can be easily site of damage and rupture so their careful design plays a decisive role. In recent years, the use of polymeric composite materials has become widespread, both in the automotive, aerospace and nautical fields. They allow advantages not only in terms of durability in aggressive environments, such as sea water or chemical industry, but also in terms of effective strength-weight ratio. In particular, the latter translates into fuel savings and a consequent reduction in costs and pollution. It is stated a weight reduction of just 1 kg, on a mid-range routing aircraft, can save up to 3000 L of fuel per year. The scientific community is making great efforts to develop high-performance and reliable connections. Among the types of composite joint, the one of interest for this study is called hybrid, as it combines two connection mechanisms: bolting and bonding. Numerous studies and experimental researches, conducted on both the two separate variants and their hybrid version, the comparison of the analyses shows the hybrid one offers better results in terms of strength and fatigue life. In this paper, virtual models are built to simulate traction tests; the results are compared to experimental ones in order to validate the numerical model. In particular, the study focuses on the pretensioning influence on the joint structural behavior.

Additive layer manufacturing (ALM) is increasingly attracting the research and industry community interest due to the several benefits provided by the layer-by-layer production approach. With respect to the surface finish, process parameters influence significantly the surface roughness. According to the State of the Art, it is found out that the roughness level may affect the structural performance of ALM products by both quasi-static and fatigue points of view. In this paper, an experimental investigation is proposed, showing that the roughness level plays a more influent role for thin components, with respect to the quasi-static response. The investigated ALM process concerns the electron beam melting technology.

Hybrid joints are a wide diffused design solution in the manufacturing industry for mechanical parts connection. The simultaneous use of two different connection mechanisms, such as bonding and bolting, allows to exploit the advantages of both techniques. There are many industrial applications where such methodology is extensively used, such as the automotive and aerospace ones. In addition to the many advantages offered by the use of hybrid joints, there are some troubles that limit their use and require the scientific research support for the development of such connections. With reference to a single lap joint, the flexural effects induced by the joint geometry are not negligible. The inhomogeneity of the joint along the load application direction inevitably determines significant bending effects, the more evident the thinner the adherends that constitute the joint. The bending effects can also lead to excessive section rotation, inducing effects of binding between washer and adherend. Such effect is even more evident in the case of polymeric composite adherends, rapidly leading the joint to a catastrophic end. In the present work some interesting experimental tests are shown, varying geometrical parameters of the joint.

Resin Transfer Molding process (RTM), is the most used technology to create large parts made by polymer matrix composites because: the production time is relative small; the consumption of materials is reduced to minimum; the obtained parts are in a constant tolerance of ±0.5mm after de-molding; both sides of the part are shiny and smooth; determinate resistance of the wall; it can be used with gelcoat on both sides or only on one; the reinforcement materials can be fiber glass, carbon fiber, sandwich materials, or metallic inserts; it does not need pressing during the curing of the resin; reduced cycle time, and low styrol emissions. In this paper the results of research regarding mathematical model of vacuum–RTM process for polymeric composites products are presented. It is taken into account that during mold filling and curing thin mold cavities, the thermal physical properties may vary from location to location and may change as a function of time. The studied material can be considered as homogeneous and isotropic. The results of applying some numerical schemes to solve the above model, corroborated with the results of the experimental measurements, can highlight the advantages of this method of mold filling.

The ever-increasing need for eco-compatibility in all sectors of industry is pushing scientific research to look for the so-called environmentally friendly materials characterized by minimal environmental impact during the manufacturing process and high recyclability. In the aeronautical sector composites are well established for primary and secondary structures, but alternative biocompatible solutions are found out even if great efforts are being required to improve their properties. In this work, the mechanical behavior of a biocomposite material is tested by implementing it in an existing numerical model of a fuselage section subject to a vertical drop test. Deformations and failures of biocomposite parts are evaluated providing indications on their possible compliance with crashworthiness and airworthiness requirements.

In the polymeric products industry, the lean production system is perceived as a solution to reduce difficulties of manufacturing automation processes complexity while reducing used resources, eliminate losses, and increase efficiency, flexibility, and profitability. Industry 4.0 is the stage of intelligent automation that exploits the latest developments in polymeric products engineering. Through implementation of information technology and the Industry 4.0 concepts in lean manufacturing 4.0 of polymeric injection molding products is a challenge that needs a strategic approach to efficient interconnection processes. The main achievements of intelligent polymeric products manufacturing system are based on the versatility and individualization of designing and manufacturing processes. The transition from lean manufacturing to Lean 4.0 manufacturing system is a complex project that requires physical production system update, transforming lean tools, build the cyber production system, define and implement Lean 4.0 tools, and connecting them into a new integrated cyber–physical system. This paper presents a strategy for identifying the transition that can be approached within an intelligent and adaptive molding cell fabrication of polymeric products industry.

The aim of the present work has been the synthesis of geopolymer composites consisting of a geoplolymer matrix, obtained by alkali activation of metakaolin, and different percentage of polyethylene glycol (PEG). The obtained composites were analyzed by Fourier transform infrared spectroscopy and scanning electron microscope in order to identify the interaction formed between the organic and the inorganic component and to investigate materials microstructure. Further, the mechanical properties of the composites were studied by traction and bending tests.

In the aircraft industry, the use of fiber reinforced materials for primary structural components over metallic parts has increased up to more than 50% in the recent years, because of their high strength and high modulus to weight ratios, high fatigue and corrosion resistance. Currently, the need of lowering weight and fuel consumption is pushing the world’s largest aircraft manufacturers in the design and building of structures entirely made of composites. Fuselage structure plays an important role in absorbing the kinetic energy during a crash. Through the deformation, crushing and damage of fuselage sub-floor structure, a survivable space inside the cabin area should be preserved during and after a crash impact in order to minimize the risk of passengers’ injuries. In this work, a Finite Element (FE) model of a full-scale 95% composites made fuselage section of a regional aircraft under vertical drop test is presented. The experiment, conducted by the Italian Aerospace Research Centre (CIRA) with an actual impact velocity of 9.14 m/s in according to the FAR/CS 25, has been numerically simulated. Two ATDs (Anthropomorphic Test Dummies), both 50th percentile, seats and belts have been modelled to reproduce the experimental setup. The results of the simulation, performed by using LS-DYNA® explicit FE code, have been validated by correlation with the experimental ones. Such comparisons highlight that a good agreement has been achieved. The presented FE model allows verifying the structural behavior under a dynamic load condition and also estimating the passive safety capabilities of the designed structure. Since the experiment is expensive and non-repeatable, a FE model can be used for Certification by Analysis purposes since, if established, it is able to virtually demonstrate the compliance to the airworthiness rules.

One of the major problems related to the use of dyes in industrial applications is their elimination from the water or soil and eventually their recovery and reutilization. In this context, a new biocompatible material, previously considered suitable for biomedical applications, is presented for the first time, as an innovative adsorbent material for wastewater treatment. A polyamidoamine-based hydrogel, prepared by Michael-type polyaddition in water, is used for efficiently adsorbing two anionic toxic textile dyes from aqueous solutions. Several parameters affecting the adsorption process, such as the pH of solutions containing dyes, the amount of hydrogel and dyes, and the effect of temperature, are investigated. Moreover, the hydrogel dehydration and swollen conditions by using dye water solution are studied by Thermo-Gravimetry (TG) and Differential Scanning Calorimetry (DSC) analyses, finding that the dehydration temperature plays a relevant role in determining the subsequent adsorbing behavior. The material characterization shows that the adsorption process can be attributed to a combination of electrostatic attraction and intermolecular interactions between hydrogel functional groups and the dye molecules. Visible absorption spectroscopy and Fourier Transform InfraRed-Attenuated Total Reflectance (FTIR-ATR) support the findings. The kinetics of the dye adsorption process are also evaluated, together with the adsorption isotherms.

Gas storage and petroleum Companies invest every year large sums of money to prevent the formation of gas hydrates plugs in flow lines as the safety requirements and the costs related to the blocking of pipelines suggest to invest in research studies to avoid the hydrate formation or to detect its presence. Gas hydrates are aggregates where hydrocarbons gas such as methane are embedded in a crystalline cage of water molecules: they can develop abruptly and block pipelines. The nucleation of hydrates and their growth occurs when methane comes in contact with water under suitable thermodynamic conditions, such as high pressures and low temperatures. Methane hydrates induce the most relevant troubles as they form with no warning and can produce partial or even full obstructions in a pipeline thus reducing flow, increasing both back- and differential pressures. If a line section is obstructed the differential pressure across the hydrate can set the plug in motion and accelerate it quickly up to a speed approaching that of sound. In that case, the moving mass can cause serious mechanical damages at locations where the plug meets such constrictions or obstacles as valves, elbows or tees. In this paper a gas pipeline failure case due to the presence of a moving hydrate plug has been investigated by using appropriate analytical and numerical models to analyse the motion of a hydrate plug as well as its impact against the pipe wall.