Francesco Marulo - Academia.edu (original) (raw)

Uploads

Papers by Francesco Marulo

Aerotecnica Missili & Spazio

Polymers

This paper shows that an eco-friendly electrospinning process allows us to produce water resistan... more This paper shows that an eco-friendly electrospinning process allows us to produce water resistant sound absorbers with reduced thickness and excellent sound-absorption properties in the low and medium frequency range (250–1600 Hz) for which which human sensitivity is high and traditional materials struggle to match, that also pass the fire tests which are mandatory in many engineering areas. The structure and composition were studied through Scanning Electron Microscopy (SEM), Fourier Transform InfraRed (FTIR) Spectroscopy and ThermoGravimetric Analysis (TGA). The density, porosity and flow resistivity were measured. Preliminary investigation of the thermal conductivity through Differential Scanning Calorimetry (DSC) shows that they have perspectives also for thermal insulation. The experimental results indicate that the achievements are to be ascribed to the chemical nature of Polyvinylpyrrolidone (PVP). PVP is, in fact, a polymeric lactam with a side polar group that may be easil...

Materials

In this work, the behaviour of thermoplastic composites and Shape Memory Alloy Hybrid Composites ... more In this work, the behaviour of thermoplastic composites and Shape Memory Alloy Hybrid Composites (SMAHCs) for aeronautical applications is analysed and compared by means of findings from numerical analyses and experimental tests. At first, experimental tests are performed by using a drop tower facility on both carbon fibre reinforced plastic samples and Carbon Fibre Reinforced Plastic (CFRP) samples hybridized with shape memory alloy materials. The materials properties and the different lower velocity impacts behaviours are simulated and validated by means of numerical models discretized in LS-Dyna explicit solver. For both configurations, the deformation mechanism for low intensity impacts, the absorbed energy, and the effect of rebounding upon the velocity change, and hence the amount of force, are investigated. Then, a configuration is prepared to withstand higher-energy impacts. Finally, the numerical analysis is extended for an innovative layup adapted on an aeronautical struct...

Materials

Graphene is an attractive component for high-performance stimuli-responsive or ‘smart’ materials,... more Graphene is an attractive component for high-performance stimuli-responsive or ‘smart’ materials, shape memory materials, photomechanical actuators, piezoelectric materials and flexible strain sensors. Nanocomposite fibres were produced by electrospinning high molecular weight Polyvinylpyrrolidone (PVP-1300 kDa) in the presence of noncovalently functionalised graphene obtained through tip sonication of graphite alcoholic suspensions in the presence of PVP (10 kDa). Bending instability of electrospun jet appears to progressively increase at low graphene concentrations with the result of greater fibre stretching that leads to lower fibre diameter and possibly conformational changes of PVP. Further increase of graphene content seams having the opposite effect leading to greater fibre diameter and Raman spectra similar to the pure PVP electrospun mats. All this has been interpreted on the basis of currently accepted model for bending instability of electrospun jets. The graphene additio...

Chinese Journal of Polymer Science

Light polymeric soundproofing materials (density = 63 kg/m 3) of interest for the transportation ... more Light polymeric soundproofing materials (density = 63 kg/m 3) of interest for the transportation industry were fabricated through electrospinning. Blankets of electrospun polyvinylpyrrolidone (average fiber diameter = (1.6 ± 0.5) or (2.8 ± 0.5) µm) were obtained by stacking disks of electrospun mats. The sound absorption coefficients were measured using the impedance tube instrument based on ASTM E1050 and ISO 10534-2. For a given set of disks (from a minimum of 6) the sound absorption coefficient changed with the frequency (in the range 200-1600 Hz) following a bell shape curve with a maximum (where the coefficient is greater than 0.9) that shifts to lower frequencies at higher piled disks number and greater fiber diameter. This work showed that electrospinning produced sound absorbers with reduced thickness (2-3 cm) and excellent sound-absorption properties in the low and medium frequency range.

Advances in aircraft and spacecraft science, 2014

Each aircraft have to be certified for a specified level of impact energy, for assuring the capab... more Each aircraft have to be certified for a specified level of impact energy, for assuring the capability of a safe flight and landing after the impact against a bird at cruise speed. The aim of this research work was to define a scientific and methodological approach to the study of the birdstrike phenomenon against several windshield geometries. A series of numerical simulations have been performed using the explicit finite element solver code LS-Dyna, in order to estimate the windshield-surround structure capability to absorb the bird impact energy, safely and efficiently, according to EASA Certification Specifications 25.631 (2011). The research considers the results obtained about a parametric numerical analysis of a simplified, but realistic, square flat windshield model, as reported in the last work (Grimaldi et al. 2013), where this model was subjected to the impact of a 1.8 kg bird model at 155 m/s to estimate the sensitivity of the target geometry, the impact angle, and the plate curvature on the impact response of the windshield structure. Then on the basis of these results in this paper the topic is focused about the development of a numerical simulation on a complete aircraft windshield-surround model with an innovative configuration. Both simulations have used a FE-SPH coupled approach for the fluid-structure interaction. The main achievement of this research has been the collection of analysis and results obtained on both simplified realistic and complete model analysis, addressed to approach with gained confidence the birdstrike problem. Guidelines for setting up a certification test, together with a design proposal for a test article are an important result of such simulations.

Rotating machineries are employed today in a wide variety of industrial applications. There are f... more Rotating machineries are employed today in a wide variety of industrial applications. There are few machines and other mechanical systems which do not include rotating components such as wheels, gears, bearings, shafts and seals. Turbines including steam, gas and wind, electrical motors and generators, turbochargers, and internal combustion engines, are just some examples of rotating machines. In the presence of rotating machineries, the so-called orders appear as multiples or fractions of the rotational speed. They can be defined as the proportional constants between the rotational speed and the frequency. The Order Tracking (OT) theory estimates the amplitude and the phase of the orders. It can be stated that during a run-up or run-down test, the measured response is mainly caused by rotational excitation. This is the main reason behind the idea to perform Operational Modal Analysis (OMA) on tracked orders rather than on the overall spectrum. It is assumed that the structure is excited by a rotating mass with increasing frequency. The excitation can be represented by two perpendicular forces of equal amplitude and in quadrature. The method considers the run-up as a multi-sine sweep excitation and combines advanced order tracking techniques with operational modal analysis to identify the modal parameters. The procedure is known as Order-Based Modal Analysis (OBMA).

Composite materials in the form of laminates or sandwich are widely used as ballistic protection ... more Composite materials in the form of laminates or sandwich are widely used as ballistic protection thanks to their excellent performance in terms of stiffness, strength and low weight. These structures are prone to various forms of damage in the event of any action outside the plan or as a result of collisions. The present work examines the phenomenon of impact from numerical point of view, using the solver LS-DYNA. The work starts from a literature research that allows to realize three numerical–experimental correlations regarding metals, composites and ceramics materials. This is fundamental to validate the cards used in the software and go to the next simulation phase with the bullet of interest. Since the first material requires excessive thickness and weight to resist to the projectile in question, composite and ceramic materials have to be used; they allow to reduce the weight and have a better impact behaviour. The present work also allows to define a numerical approach for the...

Conference Proceedings. 10th Anniversary. IMTC/94. Advanced Technologies in I & M. 1994 IEEE Instrumentation and Measurement Technolgy Conference (Cat. No.94CH3424-9), 1994

Among the advantages offered by the Artificial Neural Networks (ANNs), in the analysis and active... more Among the advantages offered by the Artificial Neural Networks (ANNs), in the analysis and active control of structures characterized by high modal densities and complexity, it should be mentioned the possibility of optimizing the number and the position of sensors and actuators. This feature can result in a sensible reduction of cost in the analysis and control of large structures

16th AIAA/CEAS Aeroacoustics Conference, 2010

Procedia Engineering, 2014

ABSTRACT During an emergency crash landing, the first requirement translates into the ability of ... more ABSTRACT During an emergency crash landing, the first requirement translates into the ability of an aeronautical structure to ensure a vital space for the occupants during an impact, and then limiting the accelerations on the occupants in terms of intensity and duration.

Wiley Encyclopedia of Composites, 2011

The noise induced inside a cylindrical fuselage model by shaker excitation is investigated theore... more The noise induced inside a cylindrical fuselage model by shaker excitation is investigated theoretically and experimentally. The NASTRAN modal-synthesis program is used in the theoretical analysis, and the predictions are compared with experimental measurements in extensive graphs. Good general agreement is obtained, but the need for further refinements to account for acoustic-cavity damping and structural-acoustic interaction is indicated.

Smart Structures and Materials 2004: Damping and Isolation, 2004

ABSTRACT The paper presents the activities performed by the authors in order to develop and valid... more ABSTRACT The paper presents the activities performed by the authors in order to develop and validate an experimental set-up for measurements of damping characteristics of typical materials employed within aeronautical and industrial field for passive vibrations reduction. These activities have been carried out within the research program funded by the European Commission named "F.A.C.E." (Friendly Aircraft Cabin Environment). The set-up has been designed to operate through a PC-based acquisition system developed in LABVIEW programming environment. The development of the experimental damping measurement set-up is based on the principle of the "Oberst beam", and it has been improved to allow the implementation of different approaches with "contacting" sensors and actuators. The influence of the damping on the stability and reliability of the results will be investigated, by evaluating the effect of the beam thickness to the applied damping thickness ratio. The results will be presented for some damping treatments like "constrained layers" as far as for rubbery materials commonly employed within the aeronautical field. These activities are aimed to the implementation of a better damping modelisation of a typical finite element model of light structures.

The program followed to attain an interior noise level similar to turbofan aircraft in a new desi... more The program followed to attain an interior noise level similar to turbofan aircraft in a new design turboprop commuter is described. The need for an early consideration, in the definition phase of the aircraft, of the acoustic requirement for configuration development is stressed, along with some peculiar characteristics of this program. After a brief presentation of features of the aircraft

Aerotecnica Missili & Spazio

Polymers

This paper shows that an eco-friendly electrospinning process allows us to produce water resistan... more This paper shows that an eco-friendly electrospinning process allows us to produce water resistant sound absorbers with reduced thickness and excellent sound-absorption properties in the low and medium frequency range (250–1600 Hz) for which which human sensitivity is high and traditional materials struggle to match, that also pass the fire tests which are mandatory in many engineering areas. The structure and composition were studied through Scanning Electron Microscopy (SEM), Fourier Transform InfraRed (FTIR) Spectroscopy and ThermoGravimetric Analysis (TGA). The density, porosity and flow resistivity were measured. Preliminary investigation of the thermal conductivity through Differential Scanning Calorimetry (DSC) shows that they have perspectives also for thermal insulation. The experimental results indicate that the achievements are to be ascribed to the chemical nature of Polyvinylpyrrolidone (PVP). PVP is, in fact, a polymeric lactam with a side polar group that may be easil...

Materials

In this work, the behaviour of thermoplastic composites and Shape Memory Alloy Hybrid Composites ... more In this work, the behaviour of thermoplastic composites and Shape Memory Alloy Hybrid Composites (SMAHCs) for aeronautical applications is analysed and compared by means of findings from numerical analyses and experimental tests. At first, experimental tests are performed by using a drop tower facility on both carbon fibre reinforced plastic samples and Carbon Fibre Reinforced Plastic (CFRP) samples hybridized with shape memory alloy materials. The materials properties and the different lower velocity impacts behaviours are simulated and validated by means of numerical models discretized in LS-Dyna explicit solver. For both configurations, the deformation mechanism for low intensity impacts, the absorbed energy, and the effect of rebounding upon the velocity change, and hence the amount of force, are investigated. Then, a configuration is prepared to withstand higher-energy impacts. Finally, the numerical analysis is extended for an innovative layup adapted on an aeronautical struct...

Materials

Graphene is an attractive component for high-performance stimuli-responsive or ‘smart’ materials,... more Graphene is an attractive component for high-performance stimuli-responsive or ‘smart’ materials, shape memory materials, photomechanical actuators, piezoelectric materials and flexible strain sensors. Nanocomposite fibres were produced by electrospinning high molecular weight Polyvinylpyrrolidone (PVP-1300 kDa) in the presence of noncovalently functionalised graphene obtained through tip sonication of graphite alcoholic suspensions in the presence of PVP (10 kDa). Bending instability of electrospun jet appears to progressively increase at low graphene concentrations with the result of greater fibre stretching that leads to lower fibre diameter and possibly conformational changes of PVP. Further increase of graphene content seams having the opposite effect leading to greater fibre diameter and Raman spectra similar to the pure PVP electrospun mats. All this has been interpreted on the basis of currently accepted model for bending instability of electrospun jets. The graphene additio...

Chinese Journal of Polymer Science

Light polymeric soundproofing materials (density = 63 kg/m 3) of interest for the transportation ... more Light polymeric soundproofing materials (density = 63 kg/m 3) of interest for the transportation industry were fabricated through electrospinning. Blankets of electrospun polyvinylpyrrolidone (average fiber diameter = (1.6 ± 0.5) or (2.8 ± 0.5) µm) were obtained by stacking disks of electrospun mats. The sound absorption coefficients were measured using the impedance tube instrument based on ASTM E1050 and ISO 10534-2. For a given set of disks (from a minimum of 6) the sound absorption coefficient changed with the frequency (in the range 200-1600 Hz) following a bell shape curve with a maximum (where the coefficient is greater than 0.9) that shifts to lower frequencies at higher piled disks number and greater fiber diameter. This work showed that electrospinning produced sound absorbers with reduced thickness (2-3 cm) and excellent sound-absorption properties in the low and medium frequency range.

Advances in aircraft and spacecraft science, 2014

Each aircraft have to be certified for a specified level of impact energy, for assuring the capab... more Each aircraft have to be certified for a specified level of impact energy, for assuring the capability of a safe flight and landing after the impact against a bird at cruise speed. The aim of this research work was to define a scientific and methodological approach to the study of the birdstrike phenomenon against several windshield geometries. A series of numerical simulations have been performed using the explicit finite element solver code LS-Dyna, in order to estimate the windshield-surround structure capability to absorb the bird impact energy, safely and efficiently, according to EASA Certification Specifications 25.631 (2011). The research considers the results obtained about a parametric numerical analysis of a simplified, but realistic, square flat windshield model, as reported in the last work (Grimaldi et al. 2013), where this model was subjected to the impact of a 1.8 kg bird model at 155 m/s to estimate the sensitivity of the target geometry, the impact angle, and the plate curvature on the impact response of the windshield structure. Then on the basis of these results in this paper the topic is focused about the development of a numerical simulation on a complete aircraft windshield-surround model with an innovative configuration. Both simulations have used a FE-SPH coupled approach for the fluid-structure interaction. The main achievement of this research has been the collection of analysis and results obtained on both simplified realistic and complete model analysis, addressed to approach with gained confidence the birdstrike problem. Guidelines for setting up a certification test, together with a design proposal for a test article are an important result of such simulations.

Rotating machineries are employed today in a wide variety of industrial applications. There are f... more Rotating machineries are employed today in a wide variety of industrial applications. There are few machines and other mechanical systems which do not include rotating components such as wheels, gears, bearings, shafts and seals. Turbines including steam, gas and wind, electrical motors and generators, turbochargers, and internal combustion engines, are just some examples of rotating machines. In the presence of rotating machineries, the so-called orders appear as multiples or fractions of the rotational speed. They can be defined as the proportional constants between the rotational speed and the frequency. The Order Tracking (OT) theory estimates the amplitude and the phase of the orders. It can be stated that during a run-up or run-down test, the measured response is mainly caused by rotational excitation. This is the main reason behind the idea to perform Operational Modal Analysis (OMA) on tracked orders rather than on the overall spectrum. It is assumed that the structure is excited by a rotating mass with increasing frequency. The excitation can be represented by two perpendicular forces of equal amplitude and in quadrature. The method considers the run-up as a multi-sine sweep excitation and combines advanced order tracking techniques with operational modal analysis to identify the modal parameters. The procedure is known as Order-Based Modal Analysis (OBMA).

Composite materials in the form of laminates or sandwich are widely used as ballistic protection ... more Composite materials in the form of laminates or sandwich are widely used as ballistic protection thanks to their excellent performance in terms of stiffness, strength and low weight. These structures are prone to various forms of damage in the event of any action outside the plan or as a result of collisions. The present work examines the phenomenon of impact from numerical point of view, using the solver LS-DYNA. The work starts from a literature research that allows to realize three numerical–experimental correlations regarding metals, composites and ceramics materials. This is fundamental to validate the cards used in the software and go to the next simulation phase with the bullet of interest. Since the first material requires excessive thickness and weight to resist to the projectile in question, composite and ceramic materials have to be used; they allow to reduce the weight and have a better impact behaviour. The present work also allows to define a numerical approach for the...

Conference Proceedings. 10th Anniversary. IMTC/94. Advanced Technologies in I & M. 1994 IEEE Instrumentation and Measurement Technolgy Conference (Cat. No.94CH3424-9), 1994

Among the advantages offered by the Artificial Neural Networks (ANNs), in the analysis and active... more Among the advantages offered by the Artificial Neural Networks (ANNs), in the analysis and active control of structures characterized by high modal densities and complexity, it should be mentioned the possibility of optimizing the number and the position of sensors and actuators. This feature can result in a sensible reduction of cost in the analysis and control of large structures

16th AIAA/CEAS Aeroacoustics Conference, 2010

Procedia Engineering, 2014

ABSTRACT During an emergency crash landing, the first requirement translates into the ability of ... more ABSTRACT During an emergency crash landing, the first requirement translates into the ability of an aeronautical structure to ensure a vital space for the occupants during an impact, and then limiting the accelerations on the occupants in terms of intensity and duration.

Wiley Encyclopedia of Composites, 2011

The noise induced inside a cylindrical fuselage model by shaker excitation is investigated theore... more The noise induced inside a cylindrical fuselage model by shaker excitation is investigated theoretically and experimentally. The NASTRAN modal-synthesis program is used in the theoretical analysis, and the predictions are compared with experimental measurements in extensive graphs. Good general agreement is obtained, but the need for further refinements to account for acoustic-cavity damping and structural-acoustic interaction is indicated.

Smart Structures and Materials 2004: Damping and Isolation, 2004

ABSTRACT The paper presents the activities performed by the authors in order to develop and valid... more ABSTRACT The paper presents the activities performed by the authors in order to develop and validate an experimental set-up for measurements of damping characteristics of typical materials employed within aeronautical and industrial field for passive vibrations reduction. These activities have been carried out within the research program funded by the European Commission named "F.A.C.E." (Friendly Aircraft Cabin Environment). The set-up has been designed to operate through a PC-based acquisition system developed in LABVIEW programming environment. The development of the experimental damping measurement set-up is based on the principle of the "Oberst beam", and it has been improved to allow the implementation of different approaches with "contacting" sensors and actuators. The influence of the damping on the stability and reliability of the results will be investigated, by evaluating the effect of the beam thickness to the applied damping thickness ratio. The results will be presented for some damping treatments like "constrained layers" as far as for rubbery materials commonly employed within the aeronautical field. These activities are aimed to the implementation of a better damping modelisation of a typical finite element model of light structures.

The program followed to attain an interior noise level similar to turbofan aircraft in a new desi... more The program followed to attain an interior noise level similar to turbofan aircraft in a new design turboprop commuter is described. The need for an early consideration, in the definition phase of the aircraft, of the acoustic requirement for configuration development is stressed, along with some peculiar characteristics of this program. After a brief presentation of features of the aircraft