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Cristina Ban

National Institute for Aerospace Research "Elie Carafoli" - INCAS, Materials and Tribology, Scientific Researcher 3rd degree/ PhD Chem Eng

University Politehnica of Bucharest, Faculty of Applied Chemistry and Material Science, Graduate Student

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Papers by Cristina Ban

Unmanned Aerial Vehicles – Classification, Types of Composite Materials Used in Their Structure and Applications

Proceedings of the 9th International Conference on Advanced Materials and Systems

Unmanned aerial vehicles (UAV) or drones, due to their versatility can be used in a wide range of... more Unmanned aerial vehicles (UAV) or drones, due to their versatility can be used in a wide range of applications, from army missions to industrial ones. With all these capabilities, the widespread use of drones in smart cities is limited, due to problems and concerns related to safety (their crash for technical reasons, collision in the air with other planes, extreme natural weather), confidentiality (hackers can use malicious applications to exploit and obtain personal data / profiles of people using the wireless location method) and security (thanks to the technology inside the drone-GPS, Wi-Fi that could be hacked/destroyed by attackers). Currently there are many types of drones classified by size, weight, altitude, endurance, landing method (VTOL, HTOL), etc. However, these parameters vary depending on the application of the drone. The performance of drones is focused on the type of built-in electronics but also on the material used to make it. All modern drones are equipped with ...

Development of a Pressure-Sensitive Coating Using Platinum Octaethylporphyrin

Coatings, Sep 10, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more

Thermo-mechanical properties of fused filament fabricated PLA at elevated temperatures

INCAS Buletin, Mar 7, 2023

This study aims to present the authors' recent research investigating the mechanical and thermo-m... more This study aims to present the authors' recent research investigating the mechanical and thermo-mechanical properties of commercial polylactic acid (PLA) polymer. Samples were manufactured by 3D printing of fused filament fabrication (FFF) and tests were performed according to ASTM International standards for polymers D638, D695 and D790. All test samples were made using the same printing process parameters. The static mechanical tests consisted of tensile and flexural loadings at various temperature ranges, from room temperature to elevated temperature (25°C, 40°C and 50°C, respectively). For ensuring that the additively manufactured products can resist severities of real-life applications, thermal stability under mechanical load tests (HDT-heat deflection temperature) were carried out. The temperature influence on the mechanical and thermomechanical properties was determined and presented, and a synthesis of the characteristics was made in accordance with the applications of products based on the studied material.

Suitability assessment of the component materials of advanced composite system for aircraft structural application

AIAA SCITECH 2023 Forum, Jan 19, 2023

High concentration hydrogen peroxide for rocket fuel applications

INCAS Buletin, Sep 1, 2020

This paper presents the experimental study of the distillation of hydrogen peroxide to increase t... more This paper presents the experimental study of the distillation of hydrogen peroxide to increase the concentration of the solution, in order to use it as rocket fuel in space applications. The process of obtaining the desired concentration required for the operation of the wind tunnel model rocket engine was obtained using the vacuum distillation method. The process consists in removing a calculated value of the water content from the hydrogen peroxide solution with a concentration of 35%, thus increasing its concentration up to the value of 90%. The key factors that contribute in obtaining the desired concentration were evaluated and experimental results were compared with the calculated values.

Mechanical Behavior of the Carbon Fibre Reinforced Plastics

ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING, Oct 28, 2021

Composite materials based on carbon fibre reinforced plastics (CFRP) have gained importance for u... more Composite materials based on carbon fibre reinforced plastics (CFRP) have gained importance for use in structural applications during the last few decades. In the present study, the tensile, flexural, shear, and comparison tests with numerical simulation are considered. The composites were obtained in the autoclave, and cured under controlled conditions, using a gradual increase of temperature. Test specimens were cut along two fiber directions, 0° and 90°, in order to compare the material behavior along these directions. The numerical simulation analysis was calculated using Nastran software. The microstructure was analyzed using optical microscopy and scanning electronical microscopy, observing the fractures, voids and fiber delamination.

Oxy-Butane Ablation Testing of Thermal Protection Systems Based on Nanomodified Phenolic Resin Matrix Materials

Polymers

Two classes of thermal protection systems composed of a carbon-fibre-reinforced (CFRP) layer and ... more Two classes of thermal protection systems composed of a carbon-fibre-reinforced (CFRP) layer and an ablative material layer joined with a thermo-resistant ceramic adhesive were developed. The two classes differ in the composition of the ablative material reinforcing compound. In the first class, the ablative material is based on micronic-sized cork granules, and in the second class, the ablative material is reinforced with carbonic felt. For both classes of thermal protection systems, the reinforcement material was impregnated in simple phenolic resin, and nanometric additive, consisting of silicon carbide nanoparticles added in two different weight contents (1 and 2% by weight) relative to the resin. The thermal conductivity for the ablative materials in the thermal protection systems structure was determined. A test facility using oxy-butane flame was developed through which the thermal protection systems developed were tested at extreme temperatures, to simulate some thermal cond...

Manufacturing process, mechanical behavior and modeling of composites structures sandwich panel

INCAS BULLETIN, 2021

The complexity of sandwich structures is a challenge for aeronautics designers. Sandwich construc... more The complexity of sandwich structures is a challenge for aeronautics designers. Sandwich construction is widely used in both the aerospace and commercial industries because it is an extremely lightweight structural approach with high rigidity and strength/weight ratios. Although today's technology offers the possibility to combine a variety of materials for these structure solutions, in aviation only a few materials are accepted. This paper presents the technological process of making these sandwich structures, as well as a study of the characterization and testing of a sandwich structure to analyze the behavior from a mechanical point of view. The conclusions of the paper represent an experimental basis on which further research will be built.

Mechanical properties of 3D printed metals

INCAS BULLETIN, 2021

The new challenges in the aerospace field lead to the need to develop new materials with complex ... more The new challenges in the aerospace field lead to the need to develop new materials with complex shapes, without major intervention in their definition. Thus, laser 3D printing technologies have been developed for both composite and metallic materials. This paper presents a study of characterization and testing of a 3D printed metal material (Maraging steel 1.2709) in three different directions (x, y and z) to observe, from a mechanical point of view, the behavior depending on the printing direction and the structural changes that intervene following the tensile stress. Mechanical tests consisted of tensile testing in accordance with current international standards, and morphostructural analyzes consisted of investigation of the failure area using optical microscopy and scanning electron microscopy (SEM), respectively.

Mechanical and tribological behaviour of PA6 and short aramid fiber composites

INCAS BULLETIN, 2021

This paper presents the results of mechanical and tribological characteristics for two composites... more This paper presents the results of mechanical and tribological characteristics for two composites: PA6 as matrix and 5% aramid whiskers as additive material and PA6 + 10% aramid whiskers, comparing them to those made of PA6 (polyamide 6). To improve the mechanical and thermal properties of polyamide (PA6), the composites were prepared via the Brabender lab mixer and mould forming under given pressure and temperature conditions. Test specimens made of pure PA6 and PA6 mixed with 5 wt.% and 10 wt.% aramid whiskers were subjected to mechanical tests (three-point bending and impact), thermo–mechanical test (HDT - heat deflection temperature), tribological test (block-on-ring) and analyzed from morpho-structural point of view. Compared to the PA6 samples, the mass concentrations of aramid whiskers improved the HDT deflection temperature values. In the case of samples with 5% aramid whiskers, the absorbed energy increased by 13% and for those with 10% aramid whiskers they increased by 30%...

Effect of Layered Silicates on Mechanical Properties of Carbon Fiber Fabric Epoxy Laminated Composites

The paper presents the obtaining, characterization and testing of hybrid composites based on mont... more The paper presents the obtaining, characterization and testing of hybrid composites based on montmorillonite layered silicates filled DGEBA (diglycidyl ether of bisphenol A) epoxy resin based matrix and carbon fiber fabric. The nanocomposite matrix was processed via ultrasonication, and the final nanofilled matrix/carbon fabric laminates were obtained by direct contact and room temperature pressing. The nanocomposite laminates were tested under tensile and 3-point bending, exhibiting overall superior mechanical performance compared to the sample without nanofiller. The results showed that 2% montmorillonite content ensures the highest strength and modulus of carbon fabric based composites.

Nanofilled EPDM composite for aerospace applications

INCAS BULLETIN, 2018

O-rings are designed to be seated in a groove and compressed during assembly between two or more ... more O-rings are designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. The joint may be static, or (in a few circumstances) may have relative motion between parts and O-ring (rotating pump shafts and hydraulic cylinders, for example). Starting from the functionality of O-rings, the component materials can be described. Synthetic rubber, EPDM (ethylene-propylene diene monomer) is one of the most popular, versatile and long-lasting elastomeric material that is suitable for a wide range of applications, such as those in the aerospace domain, presenting a good behavior in extreme temperatures and high ozone resistance. The paper presents an experimental study using EPDM − Nordel 4760, butylic rubber (IIR)− Butyl 268 and clorobutylic rubber (Cl-IIR) − Chlorobutyl HT 1066 and a nanometric agent. As the targeted application of these materials is a specific one for extreme temperatures conditions, a testing matrix was developed, aimed to qualify their technical performance. The mechanical resistance of elastomers recommends the quality of its nanomodified version through superior performance. The structure of the analyzed materials proved to be unaltered when subjected to low temperatures, exhibiting good mechanical performance suitable for the targeted application.

Thermal shock performance of carbon-bonded carbon fiber composite and ceramic matrix composite joints for thermal protection re-entry applications

Composites Part B: Engineering, 2017

Thermal shock performance of carbon-bonded carbon fiber composite and ceramic matrix composite jo... more

Mechanical Properties of Nanofilled Polypropylene Composites

INCAS BULLETIN, 2015

The paper presents a study concerning mechanical performance of thermoplastic nanocomposites base... more The paper presents a study concerning mechanical performance of thermoplastic nanocomposites based on isotactic polypropylene matrix, nanofilled with montmorillonite modified with quaternary ammonium salt and carboxyl functionalized carbon nanotubes, respectively, added in the same concentration relative to the matrix. The nanofilled and single polymer materials were obtained by simple melt compounding through extrusion process followed by injection molding into specific shape specimens for mechanical testing of the samples. Mechanical properties were evaluated by tensile and 3 point bending tests. In terms of modulus of elasticity, the results showed overall positive effects concerning the effect of nanofiller addition to the thermoplastic polymer. The fracture cross section of the tested specimens was characterized by FT-IR spectroscopy and SEM microscopy.

FP7/Space Project “HYDRA” Hybrid Ablative Development for Re-Entry in Planetary Atmospheric Thermal Protection

ABSTRACT Original approaches based on ablative materials and novel TPS solutions are required for... more ABSTRACT Original approaches based on ablative materials and novel TPS solutions are required for space applications where resistance to extreme oxidative environments and high temperatures are required. For future space exploration the demands for the thermal shield go beyond the current state-of-the-art. The most challenging missions, such as the Pioneer Venus Probe missions and the Jupiter probe Galileo were performed using the high density versions of the American FM5055 Phenolic impregnated carbon ablator (PICA) which is currently thought to be the most efficient ablation material. However, the material is derived from developments that are more than 20 years old and its procurement in Europe is doubtful. In addition, a new scenario has appeared due to a worldwide change in space mission planning strategies with entry vehicles going back to capsule designs and ablators are re-gaining attention as a result. Therefore, the development of new thermal protection materials and systems at a reasonable mass budget is absolutely essential to ensure European non-dependence on corresponding restricted technologies. HYDRA aims at the development of a novel thermal protection system through the integration of a low density ablative outer-shield on top of an advanced thermostructural ceramic composite layer and will provide an innovative technology solution consistent with the capacities of European technologies and material providers. This paper summarizes the activities at the mid-term of the project. First of all, a mission review has been performed, where the most suitable reference mission was selected in accordance with current European mission roadmaps for earth re-entry. Two types of mission have been identified: return from LEO/ISS (CTV/ARV vehicles) or the Moon (CSTS). The corresponding TPS specifications and requirements have been collected. A material state-of-the-art and a trade-off activity are underway in parallel in order to identify, select and locate candidate materials solutions. This includes a complete portfolio of current and past solutions on ablative materials, ceramic matrix composites, adhesives, integration, joints and bonds, cold and hot structures, etc.. Two types of ablators and thermostructural ceramic core combinations are envisaged, manufactured and procured for the hybrid TPS solutions. A novel TPS concept is designedthat includes local ablation modeling (aided by computed tomography) and further extension to perform a complete-system thermal analysis. In addition, a full material testing plan has been designed: thermal and mechanical characterization of the separate materials, verification of the integrity of the ablator/ceramic joints and finally an overall thermal performance assessment of the whole solution including thermal shock testing and final testing at a relevant environment at a plasma wind tunnel. For more details see www.hydra-space.eu

Thermal Performance of Ablative/ Ceramic Composite

INCAS BULLETIN, 2014

A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on ... more A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on top of ceramic matrix composites is investigated for the protection of the metallic structure in oxidative and high temperature environment of the space vehicles. The paper focuses on the joints of ablative material (carbon fiber based CALCARB® or cork based NORCOAT TM) and Ceramic Matrix Composite (CMC) material (carbon fibers embedded in silicon carbide matrix, Cf/SiC, SICARBON TM or C/C-SiC) using commercial high temperature inorganic adhesives. To study the thermal performance of the bonded materials the joints were tested under thermal shock at the QTS facility. For carrying out the test, the sample is mounted into a holder and transferred from outside the oven at room temperature, inside the oven at the set testing temperature (1100°C), at a heating rate that was determined during the calibration stage. The dwell time at the test temperature is up to 2 min at 1100ºC at an increasing rate of temperature up to ~ 9,5°C/s. Evaluating the atmospheric re-entry real conditions we found that the most suited cooling method is the natural cooling in air environment as the materials re-entering the Earth atmosphere are subjected to similar

Nanocomposites as Advanced Materials for Aerospace Industry

INCAS BULLETIN, 2012

Polymer nanocomposites, consisting of nanoparticles dispersed in polymer matrix, have gained inte... more Polymer nanocomposites, consisting of nanoparticles dispersed in polymer matrix, have gained interest due to the attractive properties of nanostructured fillers, as carbon nanotubes and layered silicates. Low volume additions (1-5%) of nanoparticles provide properties enhancements comparable to those achieved by conventional loadings (15-40%) of traditional fillers. Structural nanocomposites represent reinforcement structures based on carbon or glass fibers embedded into polymeric matrix modified with nanofillers. Structural composites are the most important application of nanaocomposites, in aerospace field, as, laminates and sandwich structures. Also, they can by used as anti-lightning, anti-radar protectors and paints. The paper presents the effects of sonic dispersion of carbon nanotubes and montmorrilonite on the mechanical, electrical, rheological and trybological properties of epoxy polymers and laminated composites, with carbon or glass fiber reinforcement, with nanoadditivated epoxy matrix. One significant observation is that nanoclay contents higher than 2% wt generate an increase of the resin viscosity, from 1500 to 50000-100000 cP, making the matrix impossible to use in high performance composites. Also, carbon nanotubes provide the resin important electrical properties, passing from dielectric to semi-conductive class. These effects have also been observed for fiber reinforced composites. Contrarily to some opinions in literature, the results of carbon nanotubes or nanoclays addition on the mechanical characteristics of glass or carbon fiber composites seem to be rather low.

Novel Hybrid Ablative/Ceramic Development for Re-Entry in Planetary Atmospheric Thermal Protection: Interfacial Adhesive Selection and Test Verification Plan

19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2014

The FP7 project HYDRA addresses the development of a hybrid thermal protection solution, where a ... more The FP7 project HYDRA addresses the development of a hybrid thermal protection solution, where a low density ablator is attached on top of a thermo-structural ceramic core by means of the use of high temperature adhesives. The project aims to design, integrate and verify a robust and lightweight thermal shield solution for atmospheric earth re-entry. The main advantage of a hybrid heat-shield is based on the capability of the thin ablative top layer to bear high thermal loads, while the tough ceramic composite underneath provides structural support.

Epoxy-Layered Silicate and Epoxy MWCNTs Nanocomposites

Applied Mechanics and Materials, 2011

The paper deals with the rheological properties of epoxy resin additivated with organically modif... more The paper deals with the rheological properties of epoxy resin additivated with organically modified montmorillonites, carbon nanotubes and nanocarbon. The paper also presents the influence of nanoadditives over composites mechanical properties. The epoxy polymer is diglycidyl ether of bisphenol A (DGEBA) and the curing agent is an aliphatic tetraamine. Organically modified montmorillonites Cloisite 30B and Cloisite 93A, MWCNTs and laser synthesized nanocarbon were used to synthesize nanocomposites by dispersing each in an epoxy resin. The dispersion was achieved through mechanical and sonic methods. The epoxy resin additivated with nanosized fillers was rheologically tested to study the dispersion influence. The sonic dispersion of nanoadditives is observed to drastically influence the rheological behavior of the suspensions. Newtonian fluid behavior disappears as the additive loading increases. The work mentions the influence of nanoadditives on the manufacturing process of epoxy ...

Development of a Pressure-Sensitive Coating Using Platinum Octaethylporphyrin

Coatings, 2021

In recent years, researchers have developed a new method of measuring the pressure on the surface... more In recent years, researchers have developed a new method of measuring the pressure on the surface using sensitive paints. This is an optical technique for determining surface pressure distributions by measuring changes in the intensity, emitted by certain excited molecules. The main advantage of the method over traditional techniques is the high resolution of the information. The only limitation of the resolution of a global map generated by the PSP (pressure-sensitive paint) technique is given by the capabilities of the image capture device. This paper describes the development of a technology for obtaining pressure-sensitive paint, in laboratory conditions, as an advanced measurement technique. The method has an application in many fields such as automotive, aerospace, or even medical.

Unmanned Aerial Vehicles – Classification, Types of Composite Materials Used in Their Structure and Applications

Proceedings of the 9th International Conference on Advanced Materials and Systems

Unmanned aerial vehicles (UAV) or drones, due to their versatility can be used in a wide range of... more Unmanned aerial vehicles (UAV) or drones, due to their versatility can be used in a wide range of applications, from army missions to industrial ones. With all these capabilities, the widespread use of drones in smart cities is limited, due to problems and concerns related to safety (their crash for technical reasons, collision in the air with other planes, extreme natural weather), confidentiality (hackers can use malicious applications to exploit and obtain personal data / profiles of people using the wireless location method) and security (thanks to the technology inside the drone-GPS, Wi-Fi that could be hacked/destroyed by attackers). Currently there are many types of drones classified by size, weight, altitude, endurance, landing method (VTOL, HTOL), etc. However, these parameters vary depending on the application of the drone. The performance of drones is focused on the type of built-in electronics but also on the material used to make it. All modern drones are equipped with ...

Development of a Pressure-Sensitive Coating Using Platinum Octaethylporphyrin

Coatings, Sep 10, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more

Thermo-mechanical properties of fused filament fabricated PLA at elevated temperatures

INCAS Buletin, Mar 7, 2023

This study aims to present the authors' recent research investigating the mechanical and thermo-m... more This study aims to present the authors' recent research investigating the mechanical and thermo-mechanical properties of commercial polylactic acid (PLA) polymer. Samples were manufactured by 3D printing of fused filament fabrication (FFF) and tests were performed according to ASTM International standards for polymers D638, D695 and D790. All test samples were made using the same printing process parameters. The static mechanical tests consisted of tensile and flexural loadings at various temperature ranges, from room temperature to elevated temperature (25°C, 40°C and 50°C, respectively). For ensuring that the additively manufactured products can resist severities of real-life applications, thermal stability under mechanical load tests (HDT-heat deflection temperature) were carried out. The temperature influence on the mechanical and thermomechanical properties was determined and presented, and a synthesis of the characteristics was made in accordance with the applications of products based on the studied material.

Suitability assessment of the component materials of advanced composite system for aircraft structural application

AIAA SCITECH 2023 Forum, Jan 19, 2023

High concentration hydrogen peroxide for rocket fuel applications

INCAS Buletin, Sep 1, 2020

This paper presents the experimental study of the distillation of hydrogen peroxide to increase t... more This paper presents the experimental study of the distillation of hydrogen peroxide to increase the concentration of the solution, in order to use it as rocket fuel in space applications. The process of obtaining the desired concentration required for the operation of the wind tunnel model rocket engine was obtained using the vacuum distillation method. The process consists in removing a calculated value of the water content from the hydrogen peroxide solution with a concentration of 35%, thus increasing its concentration up to the value of 90%. The key factors that contribute in obtaining the desired concentration were evaluated and experimental results were compared with the calculated values.

Mechanical Behavior of the Carbon Fibre Reinforced Plastics

ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING, Oct 28, 2021

Composite materials based on carbon fibre reinforced plastics (CFRP) have gained importance for u... more Composite materials based on carbon fibre reinforced plastics (CFRP) have gained importance for use in structural applications during the last few decades. In the present study, the tensile, flexural, shear, and comparison tests with numerical simulation are considered. The composites were obtained in the autoclave, and cured under controlled conditions, using a gradual increase of temperature. Test specimens were cut along two fiber directions, 0° and 90°, in order to compare the material behavior along these directions. The numerical simulation analysis was calculated using Nastran software. The microstructure was analyzed using optical microscopy and scanning electronical microscopy, observing the fractures, voids and fiber delamination.

Oxy-Butane Ablation Testing of Thermal Protection Systems Based on Nanomodified Phenolic Resin Matrix Materials

Polymers

Two classes of thermal protection systems composed of a carbon-fibre-reinforced (CFRP) layer and ... more Two classes of thermal protection systems composed of a carbon-fibre-reinforced (CFRP) layer and an ablative material layer joined with a thermo-resistant ceramic adhesive were developed. The two classes differ in the composition of the ablative material reinforcing compound. In the first class, the ablative material is based on micronic-sized cork granules, and in the second class, the ablative material is reinforced with carbonic felt. For both classes of thermal protection systems, the reinforcement material was impregnated in simple phenolic resin, and nanometric additive, consisting of silicon carbide nanoparticles added in two different weight contents (1 and 2% by weight) relative to the resin. The thermal conductivity for the ablative materials in the thermal protection systems structure was determined. A test facility using oxy-butane flame was developed through which the thermal protection systems developed were tested at extreme temperatures, to simulate some thermal cond...

Manufacturing process, mechanical behavior and modeling of composites structures sandwich panel

INCAS BULLETIN, 2021

The complexity of sandwich structures is a challenge for aeronautics designers. Sandwich construc... more The complexity of sandwich structures is a challenge for aeronautics designers. Sandwich construction is widely used in both the aerospace and commercial industries because it is an extremely lightweight structural approach with high rigidity and strength/weight ratios. Although today's technology offers the possibility to combine a variety of materials for these structure solutions, in aviation only a few materials are accepted. This paper presents the technological process of making these sandwich structures, as well as a study of the characterization and testing of a sandwich structure to analyze the behavior from a mechanical point of view. The conclusions of the paper represent an experimental basis on which further research will be built.

Mechanical properties of 3D printed metals

INCAS BULLETIN, 2021

The new challenges in the aerospace field lead to the need to develop new materials with complex ... more The new challenges in the aerospace field lead to the need to develop new materials with complex shapes, without major intervention in their definition. Thus, laser 3D printing technologies have been developed for both composite and metallic materials. This paper presents a study of characterization and testing of a 3D printed metal material (Maraging steel 1.2709) in three different directions (x, y and z) to observe, from a mechanical point of view, the behavior depending on the printing direction and the structural changes that intervene following the tensile stress. Mechanical tests consisted of tensile testing in accordance with current international standards, and morphostructural analyzes consisted of investigation of the failure area using optical microscopy and scanning electron microscopy (SEM), respectively.

Mechanical and tribological behaviour of PA6 and short aramid fiber composites

INCAS BULLETIN, 2021

This paper presents the results of mechanical and tribological characteristics for two composites... more This paper presents the results of mechanical and tribological characteristics for two composites: PA6 as matrix and 5% aramid whiskers as additive material and PA6 + 10% aramid whiskers, comparing them to those made of PA6 (polyamide 6). To improve the mechanical and thermal properties of polyamide (PA6), the composites were prepared via the Brabender lab mixer and mould forming under given pressure and temperature conditions. Test specimens made of pure PA6 and PA6 mixed with 5 wt.% and 10 wt.% aramid whiskers were subjected to mechanical tests (three-point bending and impact), thermo–mechanical test (HDT - heat deflection temperature), tribological test (block-on-ring) and analyzed from morpho-structural point of view. Compared to the PA6 samples, the mass concentrations of aramid whiskers improved the HDT deflection temperature values. In the case of samples with 5% aramid whiskers, the absorbed energy increased by 13% and for those with 10% aramid whiskers they increased by 30%...

Effect of Layered Silicates on Mechanical Properties of Carbon Fiber Fabric Epoxy Laminated Composites

The paper presents the obtaining, characterization and testing of hybrid composites based on mont... more The paper presents the obtaining, characterization and testing of hybrid composites based on montmorillonite layered silicates filled DGEBA (diglycidyl ether of bisphenol A) epoxy resin based matrix and carbon fiber fabric. The nanocomposite matrix was processed via ultrasonication, and the final nanofilled matrix/carbon fabric laminates were obtained by direct contact and room temperature pressing. The nanocomposite laminates were tested under tensile and 3-point bending, exhibiting overall superior mechanical performance compared to the sample without nanofiller. The results showed that 2% montmorillonite content ensures the highest strength and modulus of carbon fabric based composites.

Nanofilled EPDM composite for aerospace applications

INCAS BULLETIN, 2018

O-rings are designed to be seated in a groove and compressed during assembly between two or more ... more O-rings are designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. The joint may be static, or (in a few circumstances) may have relative motion between parts and O-ring (rotating pump shafts and hydraulic cylinders, for example). Starting from the functionality of O-rings, the component materials can be described. Synthetic rubber, EPDM (ethylene-propylene diene monomer) is one of the most popular, versatile and long-lasting elastomeric material that is suitable for a wide range of applications, such as those in the aerospace domain, presenting a good behavior in extreme temperatures and high ozone resistance. The paper presents an experimental study using EPDM − Nordel 4760, butylic rubber (IIR)− Butyl 268 and clorobutylic rubber (Cl-IIR) − Chlorobutyl HT 1066 and a nanometric agent. As the targeted application of these materials is a specific one for extreme temperatures conditions, a testing matrix was developed, aimed to qualify their technical performance. The mechanical resistance of elastomers recommends the quality of its nanomodified version through superior performance. The structure of the analyzed materials proved to be unaltered when subjected to low temperatures, exhibiting good mechanical performance suitable for the targeted application.

Thermal shock performance of carbon-bonded carbon fiber composite and ceramic matrix composite joints for thermal protection re-entry applications

Composites Part B: Engineering, 2017

Thermal shock performance of carbon-bonded carbon fiber composite and ceramic matrix composite jo... more

Mechanical Properties of Nanofilled Polypropylene Composites

INCAS BULLETIN, 2015

The paper presents a study concerning mechanical performance of thermoplastic nanocomposites base... more The paper presents a study concerning mechanical performance of thermoplastic nanocomposites based on isotactic polypropylene matrix, nanofilled with montmorillonite modified with quaternary ammonium salt and carboxyl functionalized carbon nanotubes, respectively, added in the same concentration relative to the matrix. The nanofilled and single polymer materials were obtained by simple melt compounding through extrusion process followed by injection molding into specific shape specimens for mechanical testing of the samples. Mechanical properties were evaluated by tensile and 3 point bending tests. In terms of modulus of elasticity, the results showed overall positive effects concerning the effect of nanofiller addition to the thermoplastic polymer. The fracture cross section of the tested specimens was characterized by FT-IR spectroscopy and SEM microscopy.

FP7/Space Project “HYDRA” Hybrid Ablative Development for Re-Entry in Planetary Atmospheric Thermal Protection

ABSTRACT Original approaches based on ablative materials and novel TPS solutions are required for... more ABSTRACT Original approaches based on ablative materials and novel TPS solutions are required for space applications where resistance to extreme oxidative environments and high temperatures are required. For future space exploration the demands for the thermal shield go beyond the current state-of-the-art. The most challenging missions, such as the Pioneer Venus Probe missions and the Jupiter probe Galileo were performed using the high density versions of the American FM5055 Phenolic impregnated carbon ablator (PICA) which is currently thought to be the most efficient ablation material. However, the material is derived from developments that are more than 20 years old and its procurement in Europe is doubtful. In addition, a new scenario has appeared due to a worldwide change in space mission planning strategies with entry vehicles going back to capsule designs and ablators are re-gaining attention as a result. Therefore, the development of new thermal protection materials and systems at a reasonable mass budget is absolutely essential to ensure European non-dependence on corresponding restricted technologies. HYDRA aims at the development of a novel thermal protection system through the integration of a low density ablative outer-shield on top of an advanced thermostructural ceramic composite layer and will provide an innovative technology solution consistent with the capacities of European technologies and material providers. This paper summarizes the activities at the mid-term of the project. First of all, a mission review has been performed, where the most suitable reference mission was selected in accordance with current European mission roadmaps for earth re-entry. Two types of mission have been identified: return from LEO/ISS (CTV/ARV vehicles) or the Moon (CSTS). The corresponding TPS specifications and requirements have been collected. A material state-of-the-art and a trade-off activity are underway in parallel in order to identify, select and locate candidate materials solutions. This includes a complete portfolio of current and past solutions on ablative materials, ceramic matrix composites, adhesives, integration, joints and bonds, cold and hot structures, etc.. Two types of ablators and thermostructural ceramic core combinations are envisaged, manufactured and procured for the hybrid TPS solutions. A novel TPS concept is designedthat includes local ablation modeling (aided by computed tomography) and further extension to perform a complete-system thermal analysis. In addition, a full material testing plan has been designed: thermal and mechanical characterization of the separate materials, verification of the integrity of the ablator/ceramic joints and finally an overall thermal performance assessment of the whole solution including thermal shock testing and final testing at a relevant environment at a plasma wind tunnel. For more details see www.hydra-space.eu

Thermal Performance of Ablative/ Ceramic Composite

INCAS BULLETIN, 2014

A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on ... more A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on top of ceramic matrix composites is investigated for the protection of the metallic structure in oxidative and high temperature environment of the space vehicles. The paper focuses on the joints of ablative material (carbon fiber based CALCARB® or cork based NORCOAT TM) and Ceramic Matrix Composite (CMC) material (carbon fibers embedded in silicon carbide matrix, Cf/SiC, SICARBON TM or C/C-SiC) using commercial high temperature inorganic adhesives. To study the thermal performance of the bonded materials the joints were tested under thermal shock at the QTS facility. For carrying out the test, the sample is mounted into a holder and transferred from outside the oven at room temperature, inside the oven at the set testing temperature (1100°C), at a heating rate that was determined during the calibration stage. The dwell time at the test temperature is up to 2 min at 1100ºC at an increasing rate of temperature up to ~ 9,5°C/s. Evaluating the atmospheric re-entry real conditions we found that the most suited cooling method is the natural cooling in air environment as the materials re-entering the Earth atmosphere are subjected to similar

Nanocomposites as Advanced Materials for Aerospace Industry

INCAS BULLETIN, 2012

Polymer nanocomposites, consisting of nanoparticles dispersed in polymer matrix, have gained inte... more Polymer nanocomposites, consisting of nanoparticles dispersed in polymer matrix, have gained interest due to the attractive properties of nanostructured fillers, as carbon nanotubes and layered silicates. Low volume additions (1-5%) of nanoparticles provide properties enhancements comparable to those achieved by conventional loadings (15-40%) of traditional fillers. Structural nanocomposites represent reinforcement structures based on carbon or glass fibers embedded into polymeric matrix modified with nanofillers. Structural composites are the most important application of nanaocomposites, in aerospace field, as, laminates and sandwich structures. Also, they can by used as anti-lightning, anti-radar protectors and paints. The paper presents the effects of sonic dispersion of carbon nanotubes and montmorrilonite on the mechanical, electrical, rheological and trybological properties of epoxy polymers and laminated composites, with carbon or glass fiber reinforcement, with nanoadditivated epoxy matrix. One significant observation is that nanoclay contents higher than 2% wt generate an increase of the resin viscosity, from 1500 to 50000-100000 cP, making the matrix impossible to use in high performance composites. Also, carbon nanotubes provide the resin important electrical properties, passing from dielectric to semi-conductive class. These effects have also been observed for fiber reinforced composites. Contrarily to some opinions in literature, the results of carbon nanotubes or nanoclays addition on the mechanical characteristics of glass or carbon fiber composites seem to be rather low.

Novel Hybrid Ablative/Ceramic Development for Re-Entry in Planetary Atmospheric Thermal Protection: Interfacial Adhesive Selection and Test Verification Plan

19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2014

The FP7 project HYDRA addresses the development of a hybrid thermal protection solution, where a ... more The FP7 project HYDRA addresses the development of a hybrid thermal protection solution, where a low density ablator is attached on top of a thermo-structural ceramic core by means of the use of high temperature adhesives. The project aims to design, integrate and verify a robust and lightweight thermal shield solution for atmospheric earth re-entry. The main advantage of a hybrid heat-shield is based on the capability of the thin ablative top layer to bear high thermal loads, while the tough ceramic composite underneath provides structural support.

Epoxy-Layered Silicate and Epoxy MWCNTs Nanocomposites

Applied Mechanics and Materials, 2011

The paper deals with the rheological properties of epoxy resin additivated with organically modif... more The paper deals with the rheological properties of epoxy resin additivated with organically modified montmorillonites, carbon nanotubes and nanocarbon. The paper also presents the influence of nanoadditives over composites mechanical properties. The epoxy polymer is diglycidyl ether of bisphenol A (DGEBA) and the curing agent is an aliphatic tetraamine. Organically modified montmorillonites Cloisite 30B and Cloisite 93A, MWCNTs and laser synthesized nanocarbon were used to synthesize nanocomposites by dispersing each in an epoxy resin. The dispersion was achieved through mechanical and sonic methods. The epoxy resin additivated with nanosized fillers was rheologically tested to study the dispersion influence. The sonic dispersion of nanoadditives is observed to drastically influence the rheological behavior of the suspensions. Newtonian fluid behavior disappears as the additive loading increases. The work mentions the influence of nanoadditives on the manufacturing process of epoxy ...

Development of a Pressure-Sensitive Coating Using Platinum Octaethylporphyrin

Coatings, 2021

In recent years, researchers have developed a new method of measuring the pressure on the surface... more In recent years, researchers have developed a new method of measuring the pressure on the surface using sensitive paints. This is an optical technique for determining surface pressure distributions by measuring changes in the intensity, emitted by certain excited molecules. The main advantage of the method over traditional techniques is the high resolution of the information. The only limitation of the resolution of a global map generated by the PSP (pressure-sensitive paint) technique is given by the capabilities of the image capture device. This paper describes the development of a technology for obtaining pressure-sensitive paint, in laboratory conditions, as an advanced measurement technique. The method has an application in many fields such as automotive, aerospace, or even medical.