Abstract The present paper describes concepts and a preliminary project of a helicopter device, t... more Abstract The present paper describes concepts and a preliminary project of a helicopter device, to investigate the use of natural fiber composites for semi-structural applications, such as electronic racks. The aim of the study consists on the evaluation of the substitution of the steel electronic rack, mounted on the helicopter Eurocopter AS 350 Ecureuil, with a new version, utilizing hemp fabric/epoxy composite material. This replacement will permit to have an environmental friendly product and lower disposal costs and weight. Lower weight for helicopters and more in general for aircraft means lower fuel consumption, lower pollution and costs. The new rack has been designed using structural static and dynamic analysis through Finite Element Method (FEM). Results are promising from the structural point of view. In fact, a weight reduction of 8.01 kg (55.6%) with respect to steel has been obtained without significantly increasing the production cost. A comparison with glass fabric/epoxy composites is also provided. The results for both the composite materials are very similar, but the advantages for the environment demonstrate that is worthy choosing natural fiber composites configuration.
International Journal of Materials and Product Technology, 2009
... Claudio Scarponi and Carlo Andreotti* ... Carlo Andreotti is a Junior Aerospace Engineer and ... more ... Claudio Scarponi and Carlo Andreotti* ... Carlo Andreotti is a Junior Aerospace Engineer and actually he cooperates in lectures and researches of the Aerospace Engineering Department of the University of Rome 'Sapienza'. ...
Journal of Reinforced Plastics and Composites, 1997
The purpose of the present paper is to provide the assessment and evaluation results of the tempe... more The purpose of the present paper is to provide the assessment and evaluation results of the temperature and lateral pressure influence on the CFRP pin loaded joints strength while they are subjected to tension. The subject study is composed of the following two main parts: 1. the Experimental Results, which are obtained through the application of four (4) different lateral pressure conditions (none, low, medium, and high), and range of temperatures (room, + 60°C, + 80°C, -55°C, -100°C, and -150°C) 2. the Theoretical Results, which are obtained through the use of 2D finite element analysis In addition, the study provides an in depth description of the employed test methodology and a comparison of the numerical and experimental final results.
Journal of Reinforced Plastics and Composites, 1999
The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply compo... more The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply composite laminates due to low-velocity impact. Three angle ply lay-up were chosen: [+30',-300]2s, [+45',-45oI2s and +60',[-60]2s. Impact tests were performed at different impact energy level and then an ultrasonic scan NDI was performed, to evaluate the internal damage. The impacted specimens were subjected to tensile load until failure occurs and the ultimate tension strength after impact was compared with the corresponding value for undamaged specimens. Moreover, for a better understanding of the failure phenomenon, some tension tests for damaged specimens were interrupted at different load levels (respectively at 30%, 60%, 85% and 90% of the corresponding failure load) and ultrasonic scans at any step were performed to evaluate the delamination growth due to tensile load. A correlation between the amount of delamination areas and the impact energy has been determined.
... By the Relative Depth Mode the ultrasonic echo delay is measured, that is the damage localiza... more ... By the Relative Depth Mode the ultrasonic echo delay is measured, that is the damage localization in terms of relative depth, as a percentage of the specimen thickness. In this case, the USD-10 is arranged in order to measure and record the level of the peak above to the ...
Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknes... more Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknesses, by means of a hemispherical impactor. The force and absorbed energy at the point of delamination initiation, the maximum force and related energy, and penetration energy ...
The purpose of this work was the evaluation of the behavior of fiber-reinforced composites and sa... more The purpose of this work was the evaluation of the behavior of fiber-reinforced composites and sandwich panels for aeronautical applications under impact. Experimental tests were performed on several specimen configurations, based on different quasi-isotropic lay-up and materials such CFRP, CFRTP and a syntactic foam as the core of sandwich panels. Considering the high specific mechanics characteristics of such a foam and its cocurability with the facesheet material, symmetric and non-symmetric sandwich configurations have been tested. The study has pointed out the advantages for aeronautic constructions of different materials and the influence of the core position along the panel thickness. The impact tests were performed with a falling weight machine, which allowed the most important dynamic and kinetic parameters, such as the contact force, impactor velocity and displacement and perforation energy to be measured. Delamination areas of each specimen were also measured using N.D.I....
Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknes... more Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknesses, by means of a hemispherical impactor. The force and absorbed energy at the point of delamination initiation, the maximum force and related energy, and penetration energy ...
In recent years, a rapid growth in the research and innovation in the natural fibre composites (N... more In recent years, a rapid growth in the research and innovation in the natural fibre composites (NFCs) sector has been experienced. The application of NFCs can in principle reduce environmental impact of synthetic fibre composites, such as fibreglass, mainly because of the renewable nature of fibres of vegetable origin. Costs would not be excessive especially in the case the fibres are a part of a large productive system, which includes other products with significant added value. Research is therefore concentrated on improving the mechanical performance of NFCs to extend their capabilities and fields of application. In this sense, entering the aeronautical sector is an ambitious, yet possibly realistic objective. However, fibre selection involves a number of aspects, including textile properties and agronomic origin of the reinforcements. The assessment of their compatibility with polymer matrices used in aviation needs also considering the issues related to fibre treatment. Specific topics are also related to aspects crucial for operation into aircraft, such as flammability and resistance to impact loading. This study provides a bibliographic review in the broad field of green composites showing the potential of their application in the near future in production of aircraft interior panels.
ABSTRACT The unremitting quest of natural and renewable materials able to replace their synthetic... more ABSTRACT The unremitting quest of natural and renewable materials able to replace their synthetic counterparts in high-performance applications has involved also sandwich structures. In this regard, the aim of this work is to characterize the impact response, in both high- and low-velocity conditions, of green sandwich structures made of agglomerated cork as core and flax/epoxy laminates as face sheets. Both bare cork, flax skins, and complete sandwich structures were subjected to impacts at three different energy levels representing the 25%, 50%, and 75% of the respective perforation thresholds. A gas gun was instead used to assess the high-velocity impact behavior of these green sandwich structures and evaluate their ballistic limit. This study shows that the buckling of cell walls of agglomerated cork enables to tailor the damage extension through-the-thickness in low-velocity impacts compared to traditional synthetic foams coupled with a considerable amount of energy absorption.
The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply compo... more The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply composite laminates due to low-velocity impact. Three angle ply lay-up were chosen: [+30',-300]2s, [+45',-45oI2s and +60',[-60]2s. Impact tests were performed at different impact energy level and then an ultrasonic scan NDI was performed, to evaluate the internal damage. The impacted specimens were subjected to tensile load until failure occurs and the ultimate tension strength after impact was compared with the corresponding value for undamaged specimens. Moreover, for a better understanding of the failure phenomenon, some tension tests for damaged specimens were interrupted at different load levels (respectively at 30%, 60%, 85% and 90% of the corresponding failure load) and ultrasonic scans at any step were performed to evaluate the delamination growth due to tensile load. A correlation between the amount of delamination areas and the impact energy has been determined.
Abstract This work addresses the damage resistance and post-impact damage tolerance of hemp fabri... more Abstract This work addresses the damage resistance and post-impact damage tolerance of hemp fabric reinforced bio-based epoxy composites subjected to low-velocity impact at energies ranging from the barely visible impact damage (BVID) threshold up to perforation. A comparison is also reported with similar composites in terms of thickness and fibre volume fraction but based on a traditional epoxy matrix. The results confirmed the significant toughness of laminates based on a bio-based epoxy matrix and their superior damage tolerance compared to standard hemp-epoxy laminates, thus highlighting their potential use in semi-structural applications due to an improved interfacial adhesion with hemp fibres.
Abstract The present paper describes concepts and a preliminary project of a helicopter device, t... more Abstract The present paper describes concepts and a preliminary project of a helicopter device, to investigate the use of natural fiber composites for semi-structural applications, such as electronic racks. The aim of the study consists on the evaluation of the substitution of the steel electronic rack, mounted on the helicopter Eurocopter AS 350 Ecureuil, with a new version, utilizing hemp fabric/epoxy composite material. This replacement will permit to have an environmental friendly product and lower disposal costs and weight. Lower weight for helicopters and more in general for aircraft means lower fuel consumption, lower pollution and costs. The new rack has been designed using structural static and dynamic analysis through Finite Element Method (FEM). Results are promising from the structural point of view. In fact, a weight reduction of 8.01 kg (55.6%) with respect to steel has been obtained without significantly increasing the production cost. A comparison with glass fabric/epoxy composites is also provided. The results for both the composite materials are very similar, but the advantages for the environment demonstrate that is worthy choosing natural fiber composites configuration.
International Journal of Materials and Product Technology, 2009
... Claudio Scarponi and Carlo Andreotti* ... Carlo Andreotti is a Junior Aerospace Engineer and ... more ... Claudio Scarponi and Carlo Andreotti* ... Carlo Andreotti is a Junior Aerospace Engineer and actually he cooperates in lectures and researches of the Aerospace Engineering Department of the University of Rome 'Sapienza'. ...
Journal of Reinforced Plastics and Composites, 1997
The purpose of the present paper is to provide the assessment and evaluation results of the tempe... more The purpose of the present paper is to provide the assessment and evaluation results of the temperature and lateral pressure influence on the CFRP pin loaded joints strength while they are subjected to tension. The subject study is composed of the following two main parts: 1. the Experimental Results, which are obtained through the application of four (4) different lateral pressure conditions (none, low, medium, and high), and range of temperatures (room, + 60°C, + 80°C, -55°C, -100°C, and -150°C) 2. the Theoretical Results, which are obtained through the use of 2D finite element analysis In addition, the study provides an in depth description of the employed test methodology and a comparison of the numerical and experimental final results.
Journal of Reinforced Plastics and Composites, 1999
The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply compo... more The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply composite laminates due to low-velocity impact. Three angle ply lay-up were chosen: [+30',-300]2s, [+45',-45oI2s and +60',[-60]2s. Impact tests were performed at different impact energy level and then an ultrasonic scan NDI was performed, to evaluate the internal damage. The impacted specimens were subjected to tensile load until failure occurs and the ultimate tension strength after impact was compared with the corresponding value for undamaged specimens. Moreover, for a better understanding of the failure phenomenon, some tension tests for damaged specimens were interrupted at different load levels (respectively at 30%, 60%, 85% and 90% of the corresponding failure load) and ultrasonic scans at any step were performed to evaluate the delamination growth due to tensile load. A correlation between the amount of delamination areas and the impact energy has been determined.
... By the Relative Depth Mode the ultrasonic echo delay is measured, that is the damage localiza... more ... By the Relative Depth Mode the ultrasonic echo delay is measured, that is the damage localization in terms of relative depth, as a percentage of the specimen thickness. In this case, the USD-10 is arranged in order to measure and record the level of the peak above to the ...
Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknes... more Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknesses, by means of a hemispherical impactor. The force and absorbed energy at the point of delamination initiation, the maximum force and related energy, and penetration energy ...
The purpose of this work was the evaluation of the behavior of fiber-reinforced composites and sa... more The purpose of this work was the evaluation of the behavior of fiber-reinforced composites and sandwich panels for aeronautical applications under impact. Experimental tests were performed on several specimen configurations, based on different quasi-isotropic lay-up and materials such CFRP, CFRTP and a syntactic foam as the core of sandwich panels. Considering the high specific mechanics characteristics of such a foam and its cocurability with the facesheet material, symmetric and non-symmetric sandwich configurations have been tested. The study has pointed out the advantages for aeronautic constructions of different materials and the influence of the core position along the panel thickness. The impact tests were performed with a falling weight machine, which allowed the most important dynamic and kinetic parameters, such as the contact force, impactor velocity and displacement and perforation energy to be measured. Delamination areas of each specimen were also measured using N.D.I....
Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknes... more Low velocity impact tests were carried out on carbon-fabric/epoxy laminates of different thicknesses, by means of a hemispherical impactor. The force and absorbed energy at the point of delamination initiation, the maximum force and related energy, and penetration energy ...
In recent years, a rapid growth in the research and innovation in the natural fibre composites (N... more In recent years, a rapid growth in the research and innovation in the natural fibre composites (NFCs) sector has been experienced. The application of NFCs can in principle reduce environmental impact of synthetic fibre composites, such as fibreglass, mainly because of the renewable nature of fibres of vegetable origin. Costs would not be excessive especially in the case the fibres are a part of a large productive system, which includes other products with significant added value. Research is therefore concentrated on improving the mechanical performance of NFCs to extend their capabilities and fields of application. In this sense, entering the aeronautical sector is an ambitious, yet possibly realistic objective. However, fibre selection involves a number of aspects, including textile properties and agronomic origin of the reinforcements. The assessment of their compatibility with polymer matrices used in aviation needs also considering the issues related to fibre treatment. Specific topics are also related to aspects crucial for operation into aircraft, such as flammability and resistance to impact loading. This study provides a bibliographic review in the broad field of green composites showing the potential of their application in the near future in production of aircraft interior panels.
ABSTRACT The unremitting quest of natural and renewable materials able to replace their synthetic... more ABSTRACT The unremitting quest of natural and renewable materials able to replace their synthetic counterparts in high-performance applications has involved also sandwich structures. In this regard, the aim of this work is to characterize the impact response, in both high- and low-velocity conditions, of green sandwich structures made of agglomerated cork as core and flax/epoxy laminates as face sheets. Both bare cork, flax skins, and complete sandwich structures were subjected to impacts at three different energy levels representing the 25%, 50%, and 75% of the respective perforation thresholds. A gas gun was instead used to assess the high-velocity impact behavior of these green sandwich structures and evaluate their ballistic limit. This study shows that the buckling of cell walls of agglomerated cork enables to tailor the damage extension through-the-thickness in low-velocity impacts compared to traditional synthetic foams coupled with a considerable amount of energy absorption.
The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply compo... more The purpose of the present paper is to evaluate the tensile strength reduction of angle-ply composite laminates due to low-velocity impact. Three angle ply lay-up were chosen: [+30',-300]2s, [+45',-45oI2s and +60',[-60]2s. Impact tests were performed at different impact energy level and then an ultrasonic scan NDI was performed, to evaluate the internal damage. The impacted specimens were subjected to tensile load until failure occurs and the ultimate tension strength after impact was compared with the corresponding value for undamaged specimens. Moreover, for a better understanding of the failure phenomenon, some tension tests for damaged specimens were interrupted at different load levels (respectively at 30%, 60%, 85% and 90% of the corresponding failure load) and ultrasonic scans at any step were performed to evaluate the delamination growth due to tensile load. A correlation between the amount of delamination areas and the impact energy has been determined.
Abstract This work addresses the damage resistance and post-impact damage tolerance of hemp fabri... more Abstract This work addresses the damage resistance and post-impact damage tolerance of hemp fabric reinforced bio-based epoxy composites subjected to low-velocity impact at energies ranging from the barely visible impact damage (BVID) threshold up to perforation. A comparison is also reported with similar composites in terms of thickness and fibre volume fraction but based on a traditional epoxy matrix. The results confirmed the significant toughness of laminates based on a bio-based epoxy matrix and their superior damage tolerance compared to standard hemp-epoxy laminates, thus highlighting their potential use in semi-structural applications due to an improved interfacial adhesion with hemp fibres.
The purpose of the present paper is to describe a new NDT technique, based on an ultrasonic syste... more The purpose of the present paper is to describe a new NDT technique, based on an ultrasonic system, in form of reflection (pulse-echo), developed by the authors. Such a technique has been successfully applied for the inspection of composite laminates, characterized by different materials (fibers and resins), thickness', stacking sequences and production processes. The sound velocity is first determined and the internal damage, in form of delaminations, is then evaluated. The technique is oriented to the determination of the position in depth and the extension of the single delaminated zones. For the purpose hardware and software can be configured in two different working modes: Maximum Amplitude Mode (MAM) and Relative Depth Mode (RDM). With the first configuration the system can record the highest reflection energy, corresponding to the bigger defect. With the second one only the first defect encountered by the ultrasonic wave on their path is recorded, but the position in depth can be evaluated (Time of Flight).
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Papers by C. Scarponi
The technique is oriented to the determination of the position in depth and the extension of the single delaminated zones. For the purpose hardware and software can be configured in two different working modes: Maximum Amplitude Mode (MAM) and Relative Depth Mode (RDM).
With the first configuration the system can record the highest reflection energy, corresponding to the bigger defect. With the second one only the first defect encountered by the ultrasonic wave on their path is recorded, but the position in depth can be evaluated (Time of Flight).