DMMCTE - MMA - Comunicaciones en Congresos y otros eventos

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Viabilidad del uso de corcho aglomerado como núcleo de estructuras sandwich sometidas a impacto
(AEMAC, 2022-08-08) Sergi, Claudia; Sánchez Sáez, Sonia; Barbero Pozuelo, Enrique; Tirillò, J.; Sarasini, F.; Ministerio de Ciencia e Innovación (España)
En la fabricación de estructuras sándwich de material compuesto, unas de las opciones más utilizadas como núcleo es el uso de espumas poliméricas. Debido al cada vez mayor esfuerzo en reducir el impacto medioambiental de los procesos industriales, existe un gran interés en incorporar materiales de origen natural que permitan disponer de fuentes renovables y que faciliten los procesos de reutilización y de reciclado. Una de las posibilidades para sustituir a las espumas poliméricas es el corcho aglomerado que presenta unas buenas propiedades mecánicas. No obstante, para que sea posible su uso como núcleo en estructuras sandwich es necesario conocer su comportamiento frente a cargas de impacto, tanto de baja como de alta velocidad. En este trabajo se compara el comportamiento de una espuma de PVC comercial con corchos aglomerados de diferentes densidades. Se ha analizado la fuerza, desplazamiento, energía absorbida y velocidad de perforación. Se ha observado que el comportamiento del corcho aglomerado puede ser similar al de una espuma polimérica convencional, aunque con un incremento de peso. Adicionalmente se ha puesto de manifiesto que el corcho aglomerado puede ser una alternativa mejor a las espumas poliméricas en aquellas aplicaciones que puedan verse sometidas a varios impactos sucesivos.
Ánalisis del comportamiento de reparaciones adhesivas sometidas a cargas estáticas
(Asociación Española de Materiales Compuestos (AEMAC), 2019-04-14) Moreno Fernández-Cañadas, Lorena María; Iváñez del Pozo, Inés; Sánchez Sáez, Sonia; Ministerio de Asuntos Económicos y Transformación Digital (España)
Los elementos estructurales de una aeronave fabricados de materiales compuestos son susceptibles de sufrir daños durante su vida en servicio. Debido al alto nivel de integración y al gran tamaño de los componentes estructurales, la sustitución completa de los componentes dañados no siempre es viable, por lo que la reparación puede suponer un gran ahorro tanto desde el punto de vista económico como temporal. Dado que las reparaciones adhesivas pueden ofrecer ciertas ventajas con respecto a las mecánicas, existe un gran interés por aumentar el conocimiento sobre su comportamiento frente a las distintas cargas estáticas a las que va a estar sometido en su vida en servicio, el cúal depende de un gran número de parámetros. En este trabajo se ha desarrollado un modelo numérico de elementos finitos implementado en Abaqus/Explicit que permite analizar la respuesta mecánica de laminados reparados frente a cargas estáticas. Se ha validado experimentalmente, usándose posteriormente para realizar ensayos virtuales de probetas reparadas con parche doble sometidas a tracción estática, analizando los resultados de fuerza máxima y rigidez al variar el tamaño y la topología (rectangulares y circulares).
Seismic analysis of the zaouiat ait mellal twin tunnels of Agadir motorway (Morocco)
(EDP Sciences, 2020) El Omari, Abdelhay; Chourak, Mimoun; Navarro Ugena, Carlos; Cherif, Seif Eddine; Rougui, Mohamed; Bakali, Hassan; Sánchez Merino, Ángel Luis
Underground structures, such as tunnels, are vital for ensuring all kinds of transportation; and being buried under the surface makes them exposed to soil dynamics. Added to the moderate seismic activity in Morocco, the stability of tunnels is put to the test. This paper examines the interaction between the ZAM (Zaouit Ait Mellal ) twin tunnels between the cities of Marrakesh and Agadir, using the Difference Element Method provided by FLAC 2D software. The acceleration is introduced as the one related to the historic event of El centro 1940 with free-field boundary conditions in the numerical model, with three configurations: tunnel 1 without tunnel 2, tunnel 2 without tunnel 1 and tunnel 1 with tunnel 2. The results of the simulations indicate that the differences values of the maximum displacement, axial force and bending moment on structural elements are very noteworthy from the configuration of the tunnel (single) to the twin tunnels in order to prove the interaction between these latter under seismic loading.
Evaluation of the geometry of single-lap adhesive joints in composite laminates
(2016) Moya Sanz, Elena María; Moreno Fernández-Cañadas, Lorena María; Iváñez del Pozo, Inés; García Castillo, Shirley Kalamis
In this work, the influence of geometry on the mechanical behaviour of single-lap adhesive joints has been analysed in order to evaluate its mechanical behaviour. Four configurations have been studied and compared: 1) single-lap joint, 2) adherends chamfering, 3) adhesive chamfering, and 4) adhesive and adherends chamfering. A 2D finite-element model has been developed using Abaqus/Standard, in which the adhesive behaviour has been defined by a Cohesive Zone Model (CZM). The analysis has been carried out in terms of failure load, peak peel stress, and peel stress distribution
Influencia de la geometría de adherentes y adhesivo en el comportamiento de uniones adhesivas a solape simple en laminados
(Universidad Rey Juan Carlos (URJC), 2015) Moya Sanz, Elena María; Moreno Fernández-Cañadas, Lorena María; Iváñez del Pozo, Inés; García Castillo, Shirley Kalamis
En las uniones adhesivas de materiales compuestos la transferencia de carga y la concentración de tensiones entre los adherentes y el adhesivo, son aspectos fundamentales a estudiar. En este trabajo se ha desarrollado un modelo numérico 2D, mediante el código de elementos finitos Abaqus/Standard, que permite estudiar uniones adhesivas a solape simple de laminados de cinta sometidos a cargas en el plano. La unión adhesivo-adherente se ha modelizado mediante el uso de elementos cohesivos, que permiten evaluar la degradación del adhesivo durante la aplicación de la carga. El modelo se ha validado comparando sus resultados con datos de carga de rotura tomados de la literatura científica. Tras la validación se ha evaluado la influencia de la variación de la geometría de los adherentes y adhesivos en el comportamiento de la unión. Se analizarán parámetros tales como la longitud de solape, el espesor del adhesivo, el escalonado del adherente y el ángulo de biselado de los adherentes y adhesivos.
Numerical simulation of dynamic TPB fracture test in a modified Hopkinson bar
(EDP Sciences, 2003-09) Loya Lorenzo, José Antonio; Fernández Sáez, José; Navarro Ugena, Carlos
Dynamic three point bending fracture tests performed in a modified Hopkinson Bar are used to obtain material fracture properties (such as the fracture-initiation toughness) at high strain rates. This work presents a three-dimensional numerical analysis of the aforementioned tests, performed by the Finite Element Method, implemented in the commercial code ABAQUS. The relationship between the Stress Intensity Factor and the Crack Mouth Opening Displacement was examined and compared with the bidinensional one, The results indicate that the use of 2D plane strain solutions can underestimate the fracture properties.
Determination of the dynamic stress intensity factor of a specimen under one-point bending from the measurement of the load-point displacement
(EDP Sciences, 2006-08) Loya Lorenzo, José Antonio; Villa, Ignacio; Fernández Sáez, José; Navarro Ugena, Carlos
The use of dynamic one-point bending tests as an alternative to three-point bending tests allows fracture properties such as dynamic initiation fracture toughness to be obtained at high strain rate. To perform this kind of test, experimental devices based on modifications of the Hopkinson bar can be used. Several authors have been proposed simplified procedures to obtain the dynamic stress intensity factor, K_I(t), considering the specimen as a Timoshenko cracked beam subjected to a concentrated load at the central cross-section. The disadvantage of this procedure is that normally it is difficult to measure the force applied to the specimen in the above-mentioned tests. Here a simplified method is proposed for the calculation of K_I(t), based on an analysis of the behaviour of a Timoshenko cracked beam, knowing the displacement of the point of loading, which can be measured more accurately than the applied load. The results were compared with those of a finite element numerical simulation and good agreement was found.
Análisis experimental del comportamiento a flexión dinámica de vigas sándwich
(2009-10) Iváñez del Pozo, Inés; Santiuste Romero, Carlos; Sánchez Sáez, Sonia
En este trabajo, se ha analizado experimentalmente el comportamiento a flexión dinámica de vigas sándwich con pieles de fibra de vidrio/poliéster y núcleo de espuma de PVC. Se han llevado a cabo ensayos dinámicos de flexión en tres puntos, de los que se ha obtenido la fuerza de contacto, la energía absorbida y el desplazamiento máximo de ambas pieles. Se ha analizado la influencia de la energía de impacto sobre estas variables y en el modo de fallo de las vigas, observando que la compresión del núcleo bajo el área de contacto provoca una localización del daño que favorece la rotura de la piel superior.
Influence of temperature on composite aeronautical structural bolted joints
(FEUP, Faculdade de Engenharia da Universidade do Porto, 2009-06) Santiuste Romero, Carlos; Barbero Pozuelo, Enrique; Miguélez Garrido, María Henar
This work focuses on the analysis of temperature and bolt torque influence on aeronautical joint behaviour. A numerical model based on finite elements was developed. Results obtained from numerical simulations showed coupled influence of temperature combined with torque level on the joint
Modelling of composite sandwich structures with honeycomb core subjected to high velocity impact
(FEUP, Faculdade de Engenharia da Universidade do Porto, 2009-06) Buitrago Pérez, Brenda; Santiuste Romero, Carlos; Sánchez Sáez, Sonia; Barbero Pozuelo, Enrique; Navarro Ugena, Carlos
In this study the behaviour of composite sandwich panels with aluminium honeycomb core subjected to high velocity impact was analysed by a numerical model which was validated by experimental tests.
Ballistic behavior of preloading CFRPs panels
(2010-10-05) García Castillo, Shirley Kalamis; Sánchez Sáez, Sonia; Barbero Pozuelo, Enrique; Navarro Ugena, Carlos
In this paper the effect of static biaxial preloading of CFRPs plates under high velocity impact is investigated experimentally. Results are compared with those obtained when no static loads are applied to the specimens. Two magnitudes were measured from the tests: the residual velocity of the impacting projectile and the extension of the damage area in the laminate.
Impact Behavior of In-plane Pre-stressed Pannels
(2005) García Castillo, Shirley Kalamis; Sánchez Sáez, Sonia; Barbero Pozuelo, Enrique; Navarro Ugena, Carlos
In this paper the behaviour of plates when they are subjected to normal impact under in-plane pre-stressed conditions was studied. Two kinds of lightweight materials were considered: aluminium alloy 7075 and quasi-isotropic glass fibre-reinforced vinylester resin. The residual velocity, the ballistic limit and, in the case of the composite material, the delaminated area, were measured in each test. Unstable cracks, that generate the catastrophic failure of the panel, were observed in the case of the aluminium at pre-stressed load levels lower than those inducing material yielding.
Impact behaviour of composite panel subjected to in-plane load
(2007) García Castillo, Shirley Kalamis; Sánchez Sáez, Sonia; López Puente, Jorge; Barbero Pozuelo, Enrique; Navarro Ugena, Carlos
This work investigates the effect that a biaxial preload causes on woven laminate panels of glass fibre and polyester matrix subjected to high-velocity transversal impact. For this, an existing analytic model based on energy considerations was used, this being modified to include the presence of a preload. The results of the analytic model for the biaxial preload state were compared with the results found for the free state of preload. Minimal difference was found between the two results. Therefore, numerical simulations were made to order to study the effect of the preload in greater detail; furthermore, experimental tests were made, validating the analytic and numerical model. In general, the two methods revealed minimal differences between the values of the ballistic limit and those of the residual velocity.
Analytical Model for Energy Absorption Capabilities of Glass/polyester Panels Subjected to Ballistic Impact
(2006-05-21) García Castillo, Shirley Kalamis; López Puente, Jorge; Sánchez Sáez, Sonia; Barbero Pozuelo, Enrique; Navarro Ugena, Carlos
This work examines the behaviour of glass/polyester panels under high-velocity impact. A theoretical analysis of the problem by an engineering model based on energy balance is validated by experimental impact tests. A gas gun was used for the tests, firing high-velocity projectiles against the panels. With the analytical model, the energy absorbed by the glass/polyester panels on impact (at velocities of 140 - 525 m/s) is calculated, and therefore the residual velocity of the projectile and the ballistic limit. Both these variables are very close to the results of the experimantal tests.
Ballistic Behaviour of PVC-FOAM sandwich structures
(2009-06) Buitrago Pérez, Brenda; García-Castillo, Shirley K.; Barbero Pozuelo, Enrique; Ferreira, António J. M.
In this paper the ballistic behaviour of sandwich plates with PVC core was analysed by means of experimental tests and an analytical model. The influence of the core in the threshold velocity and damage area of the structure was studied
Comportamiento frente a impacto de placas de vidrio/vinilester
(2005-01-06) García Castillo, Shirley Kalamis; Sánchez Sáez, Sonia; Barbero Pozuelo, Enrique; Navarro Ugena, Carlos
Los elementos estructurales de fibra de vidrio en matriz polimérica pueden verse expuestos durante su montaje, mantenimiento y vida en servicio a cargas impulsivas, lo que hace necesario estudiar su comportamiento frente a este tipo de cargas. En este trabajo realizaron ensayos de impacto sobre placas de un tejido equilibrado vidro/vinilester, utilizando los siguientes dispositivos experimentales: torre de caída, barra Hopkinson y cañón de gas, que permitieron trabajar en un rango de velocidades desde los 4 m/s hasta los 350 m/s. Se determinó la extensión del área dañada en todas las placas sometidas a impacto, por medio de técnicas de inspección no destructiva (CScan). En los ensayos de baja velocidad se midió el desplazamiento máximo de la placa; y en el caso de la torre de caída se obtuvo la energía absorbida. Por último, en los ensayos de impacto balístico se estableció la relación entre la velocidad residual y la de impacto. De los resultados obtenidos, se puede concluir que a bajas velocidades de impacto la relación existente entre la energía de impacto y la absorbida presenta una tendencia lineal; al igual que la relación entre la extensión del daño y la energía de impacto. Mientras, que para los impactos de alta velocidad se presenta un punto de inflexión a partir del cual la extensión del área dañada disminuye, con el aumento de la velocidad.
FEM analysis of dynamic flexural behaviour of composite sandwich beams with foam core
(Faculdade de Engenharia da Universidade do Porto (FEUP), 2009-06) Iváñez del Pozo, Inés; Santiuste Romero, Carlos; Sánchez Sáez, Sonia; Ferreira, Antonio J.M.
In this work, the dynamic flexural behaviour of composite sandwich beams, with glass fibre/polyester face-sheets and foam core was analysed by a numerical model. This model was validated through several dynamic flexural tests. The contact force, absorbed energy, and maximum displacement in both face-sheets were analysed.
Simulación numérica tridimensional de ensayos de fractura dinámica en dispositivos de barra Hopkinson modificada
(Grupo Español de Fractura (GEF), 2004) Loya Lorenzo, José Antonio; Fernández Sáez, José; Navarro Ugena, Carlos
[EN] This work presents a three-dimensional Finite Element analysis of Dynamic three point bending fracture tests performed in a modified Split Hopkinson Pressure Bar, including the projectile, the incident bar, the specimen and the supporting device. The influence of different parameters, such as the specimen thickness, crack length and impact velocity of the projectile on the critical stress intensity factor is analyzed. To obtain the instant at which the crack starts to grow, a local fracture criteria is applied, considering that crack begins its propagation when a critical stress at a characteristic distance of the crack tip is reached. Numerical results show that critical stress intensity factor decreases with specimen thickness, projectile impact velocity and initial crack length.
FEM analysis of dynamic flexural behaviour of composite sandwich beams with foam core
(Elsevier, 2010-08) Iváñez del Pozo, Inés; Santiuste Romero, Carlos; Sánchez Sáez, Sonia
The dynamic flexural behaviour of sandwich beams, with composite face-sheets and a foam core, was analysed by developing a 3D finite-element model. To model the core behaviour, a crushable foam model was used. The Hou criteria were used to predict the failure of the face-sheets. Dynamic bending tests were performed to validate the numerical model. The comparison between numerical and experimental results in terms of contact-force histories, peak-force values, absorbed energy, and maximum displacement of both face-sheets was satisfactory. It was revealed that the collapse of the foam core under the impact region favoured the failure of the upper face-sheet.
Modelling of composite sandwich structures with honeycomb core subjected to high-velocity impact
(Elsevier, 2010-08) Buitrago Pérez, Brenda; Santiuste Romero, Carlos; Sánchez Sáez, Sonia; Barbero Pozuelo, Enrique; Navarro Ugena, Carlos
In this study the perforation of composite sandwich structures subjected to high-velocity impact was analysed. Sandwich panels with carbon/epoxy skins and an aluminium honeycomb core were modelled by a three-dimensional finite element model implemented in ABAQUS/Explicit. The model was validated with experimental tests by comparing numerical and experimental residual velocity, ballistic limit, and contact time. By this model the influence of the components on the behaviour of the sandwich panel under impact load was evaluated; also, the contribution of the failure mechanisms to the energy-absorption of the projectile kinetic energy was determined.

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