Persona: Frövel, Malte
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Instituto Nacional de Técnica Aeroespacial
El Instituto Nacional de Técnica Aeroespacial es el Organismo Público de Investigación (OPI) dependiente del Ministerio de Defensa. Además de realizar actividades de investigación científica y de desarrollo de sistemas y prototipos en su ámbito de conocimiento, presta servicios tecnológicos a empresas, universidades e instituciones.
El INTA está especializado en la investigación y el desarrollo tecnológico, de carácter dual, en los ámbitos de la Aeronáutica, Espacio, Hidrodinámica, Seguridad y Defensa.
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Publicación Acceso Abierto Fiber bragg gratings sensor strain–optic behavior with different polymeric coatings subjected to transverse strain(Multidisciplinary Digital Publishing Institute (MDPI), 2024-04-27) González Gallego, Manuel; Terroba, Félix; Martínez Vicente, Juan Luis; González del Val, Miguel; López Cela, Juan José; Frövel, Malte; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Ciencia e Innovación (MICINN)This research work is based on a previous study by the authors that characterized the behavior of FBG sensors with a polyimide coating in a structural monitoring system. Sensors applied to structural health monitoring are affected by the presence of simultaneous multidirectional strains. The previous study observed the influence of the transverse strain (ey) while keeping the longitudinal strain constant (ex), where the x direction is the direction of the optical fiber. The present study develops an experimental methodology consisting of a biaxial test plan on cruciform specimens with three embedded FBG sensors coated with polyimide, acrylate, and ORMOCER®. Applying the Strain–Optic Theory as a reference, a comparison of the experimental values obtained with the different coatings was studied. This experimental work made it possible to study the influence of the transverse strain (ey) on the longitudinal measurements of each FBGS and the influence of the coating material. Finally, the calibration procedure was defined as well as K (strain sensitivity factor) for each sensor.Publicación Acceso Abierto A Subcell Finite-Difference Time-Domain Implementation for Narrow Slots on Conductive Panels(Multidisciplinary Digital Publishing Institute (MDPI), 2023-08-03) Ruiz Cabello Núñez, M. D.; Martín Valverde, A. J.; Plaza Gallardo, Borja; Frövel, Malte; Poyatos Martinez, David; Rubio Bretones, Amelia; Gascón Bravo, Alberto; García, S. G.; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Ciencia e Innovación (MICINN)Efficiently modeling thin features using the finite-difference time-domain (FDTD) method involves a considerable reduction in the spatial mesh size. However, in real-world scenarios, such reductions can lead to unaffordable memory and CPU requirements. In this manuscript, we present two stable and efficient techniques in FDTD to handle narrow apertures on conductive thin panels. One technique employs conformal methods, while the other utilizes subgridding methods. We validate their performance compared to the classical Gilbert-Holland model and present experimental results in reverberation environments to shed light on these models’ actual confidence margins in real electromagnetic compatibility (EMC) scenarios.Publicación Acceso Abierto Fiber Bragg Grating Sensors ice detection: methodologies and performance(Elsevier, 2022-10-16) González del Val, Miguel; Frövel, Malte; European Commission (EC)New Researches have been done recently in order to create and adapt new systems to the recent Appendix O FAR 25 Aeronautical aircraft icing regulations. One important issue are the Supercooled Large Droplets (SLD) that are an important hazard in many cases. Novel sensor technologies for aircraft are being developed in order to assess the ice severity and to discriminate between large size droplets and small size droplets ice accretions. The European SENS4ICE project gives founding for the research and development of several aeronautical ice detection systems that can discriminate between Appendix C and Appendix O conditions. In the present paper, the strengths and weaknesses of the Fiber Optic ice Detector (FOD) developed by INTA are discussed using a test matrix from the Canadian National Research Council (NRC). The FOD has presented good performance at the NRC ice wind tunnel tests in the ice detection time, detecting ice in most cases earlier than required by the actual standard (ED-103). Its lightness, low intrusiveness and small size, makes the FOD ideal for aeronautical applications. It measures indirectly the icing cloud characteristics, such as the liquid water content (LWC) and the ice accretion rate, so only an approximate severity assessment could be done.Publicación Acceso Abierto Monitorización estructural del RPAS MILANO en la fase de ensayos en vuelo(AEMAC- Asociación Española de Materiales Compuestos, 2021-04-15) Frövel, Malte; Terroba, Félix; Plaza del Pino, Juan Carlos; Cabezas, J.; Güemes, A.; García Ramírez, J.; Reyes, E.; Fernández, A.El RPAS (Remote Piloted Air System) MILANO es el mayor sistema aéreo no tripulado desarrollado por INTA, pretende convertirse en una plataforma de investigación capaz de realizar ensayos en vuelo conmultitud de cargas de pago científicas complementando de este modo a las plataformas Aéreas de Investigación (PAIs) tripuladas del propio INTA. A nivel estructural, el RPAS MILANO está realizadoen su práctica totalidad en material compuesto de carbono/epoxi de curado fuera de autoclave y en su diseño se han seguido las normativas de aeronavegabilidad aplicables al tipo de aeronave(STANAG-4671). En el mes de Diciembre del 2018 ha comenzado la fase de ensayos en vuelo del RPAS MILANO y su sistema de detección de daño y uso (SHM) se está empleando para recoger datos antes, después y durante los vuelos, proporcionando una información muy útil a la hora de evaluar y analizar el estado de la estructura y la posible aparición de sobrecargas estructurales no previstas durante la misión. La información sobre eventos especiales, como el aterrizaje forzoso o la carga de ráfagas, se puede proporcionar a los operadores de mantenimiento después de cada vuelo.El modelo de simulación y sus predicciones se han validado en una estructura real del fuselaje posterior del MILANOy en la que se introducendaños reales de tamaños mayores al eliminar remaches progresivamente. En nuestro estudio, se utilizan tres algoritmos diferentesde detección de daño, basados en un índicede daño, PCA y Artificial Neural Networks (ANN), respectivamente. The RPAS (Remote Piloted Air System) MILANO is the largest unmanned aerial system developed by INTA thataims to become a research platform capable of carrying out in-flight tests with many scientific payload, thus complementing the Air Research Platforms (PAIs) of INTA. At the structural level, the RPAS MILANO is made in its entirety in carbon / epoxy composite material that is cured out of the autoclave. Its design has been followed by the airworthiness regulations applicable to the aircraft type (STANAG-4671). In the month of December 2018, the RPAS MILANO flight test phase began and it’sHealth and Usage Monitoring System (HUMS) is being used to collect data before, after and during flights, providing very useful information when evaluating and analyzingthe state of the structure and the possible appearance of structural overloads not foreseen during the mission. Information about special events, such as forced landing or burst loading, can be provided to maintenance operators after each flight.The simulation model and its predictions have been validated in a real structure of the rear fuselage of theMILANOand in which real damage of larger sizes is introduced by eliminating rivets progressively. In our study, three different damage detection algorithms are used, based on adamageindex, PCA and Artificial Neural Networks (ANN).Publicación Restringido A subcell FDTD Scheme implementation for thin slot modeling(Institute of Electrical and Electronics Engineers, 2022-07-08) Cabello, M. R.; Martín Valverde, A. J.; Plaza Gallardo, Borja; Frövel, Malte; Poyatos Martinez, David; Rubio Bretones, Amelia; González García, S.; Instituto Nacional de Técnica Aeroespacial (INTA); Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); Junta de AndalucíaThe finite-difference time-domain (FDTD) method is not able to efficiently model thin features without a drastic reductions of the spatial mesh size, potentially yielding an unfeasible use of memory and CPU requirements. In this work we propose two stable and efficient techniques for dealing with thin apertures in FDTD, one based on conformal and one based on subgridding. These are compared, in two different scenarios, with the classical dispersive magnetic material approximation [DMMA] based on Gilbert-Holland's models.Publicación Restringido Shielding Effectiveness Measurement of an UAV Simplified Demonstrator Through Low-Level Swept Field (LLSF) Test(Institute of Electrical and Electronics Engineers, 2022-09-23) Ramos Somolinos, D.; Plaza Gallardo, Borja; Cidrás Estévez, José; Díaz Acosta, Laura; Gómez de Francisco, Patricia; Añón Cancela, M.; Frövel, Malte; Poyatos Martinez, David; Agencia Estatal de Investigación (AEI)The increasing number of electronic devices on board and the use of novel composite materials in the aerospace industry create a harsh electromagnetic environment that must be studied. In this article, a UAV demonstrator (DEMO-E3) with different test cases is evaluated through the low-level swept field test following a nested resonant chambers approach, which is framed under the high intensity radio frequency measurements. The aim is to analyze the difference in terms of the shielding effectiveness of the enclosure considering the different materials and apertures of each test sample. Some of the test cases had been previously measured independently, according to the IEC 61000-4-21 standard, while in this study, they are incorporated into the demonstrator and former results are used as a comparison.Publicación Acceso Abierto Ensayos biaxiales sobre sensores de fibra óptica basados en redes de Bragg(AEMAC- Asociación Española de Materiales Compuestos, 2021-07-19) González Gallego, Manuel; Terroba, Félix; Frövel, Malte; Moravec, C.; Martínez Vicente, Juan Luis; Serna, M. C.Los sensores de fibra óptica basados en redes de Bragg, ampliamente usados en sistemas de monitorización estructural, son sensores cuyo funcionamiento es perfectamente conocido desde el punto de vista teórico cuando son sometidos a deformaciones en la dirección de la propia fibra. No obstante, las deformaciones transversales tienen efecto en el comportamiento de la fibra óptica como sensor, aunque dicho efecto ha sido menos estudiado y es menos conocido. Cuando un sensor se encuentra embebido en una estructura de material compuesto, sudeformación rara vez es unidireccional, debido a la presencia de estados de carga complejos o al efecto que el módulo de Poisson tiene sobre la deformación del propio laminado.El objetivo del trabajo es someter al sensor a un estado de deformación controlado en los dos ejes del plano principal mediante la aplicación de cargas perpendiculares entre sí. Para ello, se va a realizar una campaña de ensayos biaxiales sobre probetas de material compuesto con sensores de fibra óptica embebidos. Con esta metodología de ensayos en el plano, se observará la influencia de las deformaciones transversales en los valores de deformación longitudinal medidos por el sensor.Para la realización de los ensayos biaxiales se ha utilizadouna máquina de ensayos que permite controlar las cargas aplicadas en las tres direcciones espaciales de forma independiente y un equipo de medición de deformaciones mediante correlación digital de imagen (CDI). De esta forma, se realizará una caracterización del sensor antes dicho bajo un estadode cargas. Bragg Grating based optical fibre sensors are widely used for structural monitoring. Its operation is theoretical well known when deformations are measured along the fibre axes. Nevertheless, transversedeformations of the optical fibre have an effect thataffects the performance of the sensors. This transverse effect has not been so deeply studied as the longitudinal and it is less known. When a sensor is embedded in a composite structure, its deformation is rarely unidirectional because of the presence ofcomplex loads cases and/or the Poisson module effect on the deformation of the lamination. A test campaign of biaxial composite material specimens with embedded fibre optic sensors is going to be performed. The work pursues to create controlled deformation cases to the sensor in the two main axes of its plane, by means of perpendicular loads in each axis. Following this test methodology in the plane, it will be observed the influence of the transverse deformations on the values of the longitudinal deformation measured by the sensors. To carry out the biaxial tests it has been used equipment that allows the control of the applied load in the three coordinate axes independently. It also been used a digital image correlation (DIC) equipment for measuring the deformations. Characterization of the sensors will be carried out with different load case tests.Publicación Restringido Structural health and usage monitoring of an unmanned turbojet target drone(SAGE, 2018-03-22) Terroba, Félix; Frövel, Malte; Atienza, R.Aerial target drones are an important tool for the training of anti-air batteries and missiles for defense and homeland protection. These target drones are highly loaded structures that require a reliable inspection after each flight. A health and usage monitoring system based on load path changes has been developed. These changes are measured with fiber optic Bragg grating sensors which have been implemented in high loaded structural parts of the fuselage of the DIANA IA, which is operated by the Spanish National Institute for Aerospace Technology. The health and usage onitoring system has been tested and calibrated by destructive tests, introducing defined damages in fuselage stringers and evaluating the structural damage by the measured strain distribution. The tests have shown that a simple system based on four fiber optic Bragg grating sensors is able to detect barely visible structural damages in the entire high loaded front fuselage of the drone. The health and usage monitoring system requires only on-ground equipment and enables a fast turnaround of the drone after each flight. Two DIANAs have been instrumented for their application in service. First flight tests have been performed and the performance of the health and usage monitoring system has been evaluated.Publicación Acceso Abierto Thermal expansion calculation using FBGS in cryogenic applications(Elsevier, 2024-09-15) González del Val, Miguel; Martínez Olmo, José Manuel; Terroba, Félix; Cabrerizo, F.; Turon, Albert; Renart, J.; Frövel, Malte; Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI)This study presents the measurement of the thermal expansion of aluminum alloy 6061 at cryogenic temperatures using Helium as the cooling medium. Three distinct tests were conducted to evaluate thermal expansion: two with gradual and natural heating of the material, and a third with temperature stabilization at key points. Measurements were carried out using Fiber Bragg Grating Sensors (FBGS), which provided precise and reliable data on the material's thermal behavior. The obtained results were compared with reference curves from the National Institute of Standards and Technology (NIST), showing good agreement and validation of the employed methods. This research highlights the effectiveness of using FBGS in measuring thermal expansion under cryogenic conditions and the importance of heating procedures in obtaining accurate data.Publicación Acceso Abierto Los materiales compuestos en el ICTS-CEHIPAR(AEMAC- Asociación Española de Materiales Compuestos, 2021-01-18) Martínez Vicente, Juan Luis; González Gallego, Manuel; Terroba, Félix; Frövel, Malte; Valle, Jesús; de la Rosa Escribano, Juan Carlos; Serna, M. C.; Martínez, J. L. [0000-0001-9046-8237]El Centro de Experiencias Hidrodinámicas de El Pardo (ICTS-CEHIPAR), considerado como Infraestructura Científica y Técnica Singular (ICTS), es parte de la Subdirección General de Sistemas Navales (SGSN) del Instituto Nacional de Técnica Aeroespacial “Esteban Terradas” (INTA). En el Departamento de Tecnología y Ensayos del ICTS-CEHIPAR, se ha creado recientemente una línea de investigación aplicada a la industria naval y centrada en el estudio de materiales compuestos. En esta línea de investigación se ha marcado como objetivo la monitorización de esfuerzos estructurales en materiales compuestos mediante sensores de fibra óptica en redes de Bragg de difracción (FBGS). Desde el ICTS-CEHIPAR se persigue la mejora de los procedimientos constructivos de modelos para buques y artefactos navales y por ello, el uso de materiales compuestos en estos procedimientos. En este sentido, la implementación de técnicas de instrumentación para la monitorización de esfuerzos en dichos materiales es necesaria para detectar posibles daños debidos a diferentes causas que pueden ocurrir a lo largo de su vida útil. Los resultados obtenidos en los ensayos a escala permitirán aplicar a buques reales las metodologías de fabricación e instrumentación estudiadas, con el fin de incrementar su seguridad y optimizar su mantenimiento.
