Ponencias (Mecánica de Medios Continuos y Teoría de Estructuras)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11399

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A Multi-pronged Approach to Promote Pedagogical Innovation and Distance Learning in Higher Education
(Springer, 2025) Marques, Célio Gonçalo; Nata, Ana; Ferreira, Luis Miguel Marques; Rodrigues, Ana Marta; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Carvalho, J.V.
In an ever-changing society, it is of utmost importance that education offers methods and tools that foster a more dynamic and participatory teaching and learning experience, tailored to the needs of today's students. Consequently, the pursuit and implementation of active learning and distance learning approaches have become imperative in higher education. This study presents effective practices devised at a Higher Education Institution in Portugal, aimed at promoting pedagogical innovation among faculty members and enhancing distance learning. The work highlights various activities that support digital empowerment, as well as strategic research and development initiatives, which can serve as valuable guidelines for other higher education institutions. Furthermore, drawing upon three years of collected data, the impact of these activities on the faculty, the institution, and the community was evaluated. Overall, the results demonstrate that the multi-pronged approach has had a positive influence on teaching practices and has positively affected the organizational dynamics. It underscores the critical nature of continuous investment in specialized training and research and development endeavours.
Vibration-based NDT system for external tendons: Anomaly detection through machine learning classifiers
(CRC Press, 2024) Naranjo Pérez, Javier; Jiménez Alonso, Javier Fernando; Muñoz Díaz, Iván; García Palacios, Jaime H.; Concha Renedo, Carlos Martín de la; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Jensen, Jens Sandager; Frangopol Dan M.; Schmidt, Jacob Wittrup; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
This paper proposes a new prototype for the non-destructive testing of external post-tensioning tendons. The system is based on the dynamic response of the tendon from which a series of structural performance indicators are identified, allowing to assess them and to make maintenance or replacement decisions in case anomalies are detected. The prototype developed is economical, easy to use, scalable (more sensors or performance indicators can be included) and portable, since all the necessary equipment is placed on a trolley. The system has been used for the evaluation of the external post-tensioning tendons of a 12-span railway bridge, with a total of 202 tendon segments analyzed. For each test, the system generates a report summarizing the calculated indicators and pointing out any anomalies detected. Considering the results of all the segments, an unsupervised clustering technique is applied to create groups with similar patterns where the results obtained are classified and the presence of outliers, i.e. tendon sections with anomalous behavior, is checked.
On the assessment of the vibrational response of highly-skewed high-speed railway bridges
(CRC Press, 2024) Martínez-Rodrigo, María Dolores; Sánchez-Quesada, Juan Carlos; Moliner, Emma; Romero Ordóñez, Antonio; Galvín, Pedro; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Generalitat Valenciana; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
The aim of this study is to evaluate the vertical vibrational response of simply-supported (SS) highly-skewed railway bridges. Configurations of interest are pre-stressed concrete girder deck bridges with and without end transverse diaphragms from conventional and High-Speed (HS) lines. Two detailed 3D Finite Element (FE) numerical models including the ballast track are implemented and updated from experimental modal data from two real bridges of approximately 15 and 25 m of span lengths. The evolution of modal parameters and maximum acceleration under passing trains is investigated for several variants of the reference models. Conclusions regarding the effect of skewness correlated with the execution procedure of the transverse diaphragms are finally extracted.
Integrating CWT and CNN for damage detection in high-speed railway bridges
(CRC Press, 2024) Jiménez Alonso, Javier Fernando; Naranjo Pérez, Javier; Renedo, Carlos M.C.; García-Palacios, Jaime H.; Muñoz Díaz, Iván; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP245: Ingeniería de las estructuras
High-speed railway bridges, reinforced by external post-tensioning systems, are prone to suffer from fatigue problems under corrosion environments. In order to perform the structural assessment of these structures, during their overall life-cycle, structural health monitoring strategies are currently being implemented. Among the different strategies, vibration-based ones are normally employed in civil engineering applications due to its ability to global damage detection. According to these strategies, the measured dynamic response of the structure is compared between two states (the current and the original one) in order to assess the performance level. Nowadays, deep learning, a machine-learning computational tool, has been used to assist in this comparison task. An artificial neural network is usually trained for this purpose. For this training process, two extreme states are normally considered: (i) undamaged state; and (ii) damaged state. As it is not normally possible to obtain data of the damaged state of the structural system, an updated physics-based model is usually considered for this purpose. Therefore, the dynamic response of the damaged structure is simulated based on this updated model. In this manuscript, the performance of a classifier is assessed when it is implemented for the damage detection of a high-speed railway bridge. As an original (undamaged) state, an updated Bayesian finite-element-model of the structure is considered. Different level of uncertainty has been considered (variation range of the updating parameters) for this updated model. As damaged state, different levels of numerical damage have been generated. The dynamic response of the structure (vertical accelerations) has been compared for the damage detection. For the feature extraction, the continuous wavelet transform has been considered. As deep learning technique, a pre-trained convolutional neuronal network has been taken into account. Thus, the performance of the proposed classifier has been assessed, for this particular case-study, via the determination of both the confusion matrix and the accuracy ratio. Finally, the variation of the accuracy ratio in terms of the uncertainty of the updated model and the damage level has been studied in detail.
Data-driven framework for damage detection in structural system
(CRC Press, 2024) Ghiasi, R.; Jiménez Alonso, Javier Fernando; Malekjafarian, A.; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Science Foundation Ireland (SFI); Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
This paper presents an automated methodology for data-driven damage detection (DD) based on feature extraction from the measured vibration responses of civil engineering structures subjected to ambient/operational conditions. To do so, after recording the dynamic response of the structure, feature extraction is performed in the time domain and then the best subset of measurement features that characterize the state of the structure is selected using Analysis of Variance (ANOVA) algorithm. Finally, DD is performed using a machine learning (ML) algorithm trained with selected features. To test the proposed framework, a dataset from a laboratory steel structure is used, and two supervised ML algorithms, K-nearest neighbor classification (KNN) and artificial neural network (ANN) were applied in order to classify damage states. The results showed that both classification techniques were able to successfully classify damage. In addition, the impact of using different feature extraction/selection methods on the accuracy of the proposed approach is studied in detail.
Modal identification and soil-structure interaction analysis of a portal frame railway bridge
(CRC Press, 2024) Chordà-Monsonís, Josep; Sánchez-Quesada, Juan Carlos; Moliner, Emma; Martínez-Rodrigo, María Dolores; Romero Ordóñez, Antonio; Galvín, Pedro; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universitat Jaume I; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Generalitat Valenciana; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
The dynamic response of portal frame bridges is influenced by soil-structure interaction. Due to the complexity of the phenomenon, predicting its dynamic behaviour is difficult and time-consuming. For this reason, this interaction is rarely considered in the numerical analyses. However, recent research is providing further evidence about the importance of considering it to avoid discrepancies between numerical and experimental results. In this contribution, a study on an existing portal frame railway bridge is carried out. First, the determination of its modal parameters is addressed. Then, a 3D finite-element numerical model of the bridge is implemented considering the track, track-bridge-soil system. Perfectly matched layers are considered at the model boundaries. The results obtained with this model are employed to implement a simplified version on which the soil is substituted by a series of spring-dashpots. After calibration, a comparison is carried out with the experimental and numerical modes of the bridge.
Machine learning-based clustering and regression for assessing temperature-induced variations on external tendon’s natural frequencies
(CRC Press, 2024) Chillitupa-Palomino, L.; Barrera-Vargas, Christian A.; García-Palacios, Jaime H.; Muñoz Díaz, Iván; Naranjo Pérez, Javier; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
Vibration-based techniques for external post-tensioning tendons have been used as non-destructive technique to assess their mechanical behavior. Thus, the continuous monitoring allows to assess their deterioration process through the continuous tracking of their natural frequencies, which may be used as damage indicators and for continuous force estimation. Hence, temperature dependencies on the frequency spectra of natural frequencies may mask potential damage among other problems such as double peaks or the existence of bracing systems. In this sense, this paper presents a mixed-cascade clustering for the frequency tracking together with the application of regression models (including linear regression and nonlinear autoregressive with exogeneous input neural network) to the classified data for identification of temperature dependencies. The proposed methodology has been applied to a case of study corresponding to several monitored tendons on a railway continuous concrete bridge.
Application of dynamics inversion techniques to the force control of electrodynamic actuators used for active vibration absorption
(IOP Publishing, 2024) Ramírez-Senent, José; Díaz, Iván M.; García-Palacios, Jaime H.; Jiménez Alonso, Javier Fernando; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP245: Ingeniería de las estructuras
The active vibration absorber has been successfully used, both in laboratory and actual facilities, to mitigate the human-induced vibrations taking place in lively, low-damping structures such as long-span floors or pedestrian footbridges. Nonetheless, the dynamic behavior of the electrodynamic proof-mass actuators employed for this purpose may negatively affect the overall vibration attenuation features due to the interaction with the motion of the structure under optimization. In this paper, the utilization of dynamic inversion techniques to improve the force control of electrodynamic proof-mass actuators is presented. The main idea behind this approach is to find an approximate inverse model of the actuator dynamics which, upon implementation on a real-time controller, leads to an approximate cancellation of actuator dynamics, making it behave closer to an ideal one. The selected way of proceeding also accounts for the actuator-structure interaction phenomenon. This approach may be employed to improve the performance of any force-based vibration control algorithm. Herein, the dynamic inversion techniques are applied to the well-known Direct Velocity Feedback algorithm which aims at emulating the behavior of a dashpot connected between the control point and the ground in its simplest version. The goodness of the proposed procedure has been assessed both by experimental tests performed over a full-scale composite material pedestrian footbridge existing at the School of Civil Engineering of the Technical University of Madrid. The test results show that the dynamic inversion approach improves the force tracking of the proof-mass actuator to a great extent, therefore yielding better attenuation results that those achieved with the classical Direct Velocity Feedback scheme.
Design and optimisation of 3D-printed energy harvesters for railway bridges
(IOP Publishing, 2024) Cámara Molina, Javier Cristóbal; Romero Ordóñez, Antonio; Galvín, Pedro; Moliner, Emma; Martínez-Rodrigo, María Dolores; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Junta de Andalucía; Generalitat Valenciana; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
This paper investigates energy harvesting on railway bridges. The type of harvester studied is a cantilever bimorph beam with a mass at the tip and a load resistance. These parameters are adjusted to find the optimal design that tunes the harvester to the fundamental frequency of the bridge. An analytical model based on a variational formulation to represent the electromechanical behaviour of the device is presented. The optimisation problem is solved using a genetic algorithm with constraints of geometry and structural integrity. Additive manufacturing to 3D print energy harvesters is used to maximise design flexibility and energy performance. The proposed procedure is implemented in the design and manufacture of an energy harvesting device for a railway bridge on an in-service high-speed line. The structure under study corresponds to a six-arched concrete bridge with double ballasted track. The proposed design is experimentally validated and the performance under operating conditions is evaluated in a test field.
Numerical assessment of the dynamic load allowance on long-span modular steel bridges considering vehicle-bridge interaction
(IOP Publishing, 2024) Chordà-Monsonís, Josep; Moliner, Emma; Martínez-Rodrigo, María Dolores; Zacchei, Enrico; Tadeu, Antònio; Romero Ordóñez, Antonio; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Junta de Andalucía; European Commission. Fondo Social Europeo (FSO); Generalitat Valenciana; Universitat Jaume I
Dynamic effects caused by vehicles on bridges is a key aspect to consider on the designing, monitoring and maintenance of the roadway infrastructure. This is particularly important in the case of modular truss bridges as they face operational restrictions when spans lengths are larger than 60 m. In the recent years, new efforts are being directed to develop fully-functional modular steel bridges of substantially larger spans. For this purpose, it is essential to fully understand the dynamic effect of vehicles on such structures. This paper provides a detailed study on two modular steel bridges considering span lengths from 120 to 140 m. A 3D coupled vehicle-bridge model is used to simulate the vehicle-bridge interaction and evaluate the dynamic load allowance of the structures. Different profiles of road irregularities are generated and their influence is investigated. The results reveal the importance of defects that excite vertical bouncing modes of the vehicle. The effects of considering different span lengths and vehicle speeds are also discussed. Finally, the dynamic load allowance obtained for the bridges under study is compared to that calculated with the expressions given in several design codes.
Propiedades mecánicas en fatiga de un hormigón de muy altas prestaciones mediante ensayos de flexión en 3 puntos
(Asociación Científico-Técnica del Hormigón Estructural (ACHE), 2017-06) Ríos Jiménez, José David; Cifuentes-Bulté, Héctor; Medina Encina, Fernando; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Economía y Competitividad (MINECO). España
En este trabajo, se ha estudiado el comportamiento a fatiga de un hormigón de muy alta resistencia. Para ello, se ha diseñado una campaña experimental con dos hormigones diferentes, pero con la misma matriz. Uno de ellos no estaba reforzado con fibras de acero, D1, y el otro reforzado, DF1. Los ensayos a fatiga se realizaron sobre probetas prismáticas con entalla, a flexión en tres puntos. A partir de los datos experimentales, se determinaron las correspondientes curvas S-N mediante una metodología estadística desarrollada por Castillo y Fernández-Canteli y aplicada a través del software ProFatigue desarrollado por sus correspondientes equipos de trabajo.
Influencia del tiempo de exposición de temperaturas en el comportamiento en fractura de hormigones autocompactantes reforzados con fibras de polipropileno
(Asociación Científico-Técnica del Hormigón Estructural (ACHE), 2017-06) Ríos Jiménez, José David; Cifuentes-Bulté, Héctor; Leiva Fernández, Carlos; Medina Encina, Fernando; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Economía y Competitividad (MINECO). España
El presente estudio está centrado en el efecto de la adición de fibras de polipropileno, de diferente longitud, al comportamiento en fractura de un hormigón de alta resistencia sometido a diferentes niveles de temperatura y tiempos de exposición. La longitud de las fibras debe influir en estas propiedades, ya que se sabe que cuanto mayor es la longitud, mayor es la resistencia del hormigón reforzado frente a la rotura. Esto es de gran interés para la aplicación de este tipo de hormigones en sistemas de almacenamiento de energía termo solar. En estas aplicaciones, el hormigón es uno de los materiales de mayor interés por su capacidad térmica de almacenamiento, su trabajabilidad, disponibilidad y bajo coste.
Determinación de las curvas de Wöhler en fatiga a flexotracción de un hormigón de muy alta resistencia sometido a temperatura elevada
(Editorial Universitat Politècnica de València, 2018) Ríos Jiménez, José David; Cifuentes-Bulté, Héctor; Medina Encina, Fernando; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Economía y Competitividad (MINECO). España
El uso de hormigones de muy alta resistencia en depósitos de almacenamiento de energía es una de las aplicaciones en las que se está estudiando la idoneidad de su uso frente a otros tipos de materiales. Las principales ventajas que aporta está opción son la de ser un material resistente, con capacidad para almacenamiento de energía térmica y todo ello para un material accesible y de bajo coste en comparación con otras alternativas. En el proceso de almacenamiento se pueden alcanzar temperaturas que rondan los 300 ºC durante periodos prolongados de tiempo. El estudio de la durabilidad de estas estructuras en periodos con exposición de cargas variables y temperatura, así como los posibles daños ocasionados en la matriz de hormigón, son de gran importancia debido a las consecuencias que pueden propiciar. En este trabajo nos hemos centrado en el estudio del comportamiento frente a fallo por fatiga a flexotracción de un hormigón de muy alta resistencia diseñado por nosotros. Para ello se han realizado dos amasadas idénticas de hormigones reforzados con fibras de acero. Todos los hormigones con la idéntica matriz y una relación de fibras de un 2.5% en volumen. Los hormigones fueron reforzados con dos tipos de fibras diferentes: una de ellas el modelo RC-80/35-BN, de 35 mm de longitud y extremos en forma de gancho, y otra el OL-13/0.16, de 13 mm de longitud y extremos lisos, ambas de Bekaert. La primera amasada fue ensayada a temperatura ambiente y la segunda, fue calentada hasta 300 ºC. La temperatura de cada amasada estuvo durante un período de al menos 24 horas, de manera que se asegurase que cualquier punto de la matriz alcanzase dicha temperatura. Se realizaron ensayos a fatiga de flexión en tres puntos sobre probetas prismáticas de 440x100x100 mm condicionadas por un defecto local inicial reproducido mediante una entalla, de 1/6 del canto, en la zona central de la probeta. A partir de los resultados experimentales se obtuvieron las curvas de Wöhler de cada uno de los hormigones y se realizó un análisis de las mismas relacionándolo con las propiedades mecánicas de los hormigones y una comparativa del efecto de la temperatura en la vida útil del material.
Efectos de la temperatura y la presencia de fibras de acero en la microestructura de hormigones de ultra altas prestaciones y su influencia en el comportamiento en fractura
(Secretaría del Grupo Español de Fractura, 2019-04) Ríos Jiménez, José David; Afán, Alicia; Cifuentes-Bulté, Héctor; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Economía y Competitividad (MINECO). España
El objetivo principal de este trabajo es determinar el efecto de la temperatura y la adición de fibras de acero de diferente longitud en la microestructura de la matriz de hormigones de muy altas prestaciones y establecer una conexión causaefecto con el comportamiento en fractura que presentan dichos hormigones. Se fabricaron cuatro tipos de hormigones con idéntica matriz pero diferente tipo de refuerzo. Para la determinación de las propiedades en fractura, se llevaron a cabo ensayos de flexión en cuatro puntos de cada uno de los hormigones a 300 oC y fueron comparados con idénticos ensayos a temperatura ambiente previamente realizados por los autores. La influencia de la temperatura y del refuerzo de fibras en la microestructura de la matriz fue analizado mediante el uso de tomografía computarizada de rayos X. A partir de los resultados, se observó como la adición de fibras de acero de menor longitud redujo la porosidad de manera más efectiva y con ella se alcanzó la mayor resistencia del material. Sin embargo, las fibras de mayor longitud permitieron mayores deformaciones que conllevó a una mayor energía de fractura.
Impact Performance of Composite Sandwich Shells with Cork Core
(Springer, 2024) Ferreira, Luis Miguel Marques; Coelho, Carlos A.C.P.; Reis, Paulo Nobre Balbis; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Torres Hernández, Yadir; Fundação para a Ciência e a Tecnologia. Portugal; Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
Composite sandwich structures have gained significant attention in engineering applications due to their exceptional strength-to-weight ratio, stiffness, and energy absorption capabilities. One promising core material is cork, which possesses desirable characteristics such as low density, high compressive strength, and good energy absorption capacity. This study aimed to compare the impact performance of composite shells with composite sandwich shells featuring an agglomerated cork core, while investigating the influence of semicylindrical shell diameters. The results underscore the significant impact of specimen diameter on the performance of these structures. Larger diameter specimens (106 mm) exhibited notably higher maximum force, albeit with lower maximum displacement, energy absorption, and contact time compared to those with smaller diameter (82 mm). Similar trends were observed in composite sandwich shells. Furthermore, the inclusion of cork in composite sandwich shells marginally reduced strength of the specimens. For identical diameters, both configurations exhibited comparable maximum force and displacement. However, composite sandwich shells with a cork core absorbed less energy than those without a cork core. This behaviour persisted across both shell geometries, with slightly higher percentage differences observed in the larger diameter specimens.
Quadrature rule for solving the Helmholtz equation in hypersingular BEM formulation
(WIT Press, 2023) Romero Ordóñez, Antonio; Velázquez-Mata, Rocío; Domínguez Abascal, José; Tadeu, Antonio; Galvín, Pedro; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
Velázquez-Mata et al. recently presented a quadrature rule to accurately evaluate singular and weakly singular integrals in the sense of the Cauchy Principal Value by an exclusively numerical procedure. The procedure was verified by solving engineering problems using the boundary element method with fundamental solutions that have singularities of type log(r) and 1/r. However, that quadrature does not handle the evaluation of the Hadamard Finite Part of hypersingular integrals. These types of singularity appear in several fundamental solutions and, also, when the hypersingular boundary element formulation is applied to the Green functions previously analysed by the authors. In this paper, the quadrature rule presented in Velázquez-Mata et al. is extended to accurately compute integrals with singularities of the type 1/r2. The quadrature weights are derived from a system of equations defined from the finite part of known integrals called generalised moments, which include the element shape functions. This novelty is included in the hypersingular formulation of the boundary element method to solve the Helmholtz equation, taking advantage of this methodology to consider null-thickness boundaries using the Dual BEM.
Optimal design and application of 3D printed energy harvesting devices for railway bridges
(CRC Press, 2023) Cámara-Molina, J.C.; Romero Ordóñez, Antonio; Galvín, Pedro; Moliner, Emma; Martínez-Rodrigo, María Dolores; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia, Innovación y Universidades. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Centro Informático Científico de Andalucía (CICA); Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
In this paper, the authors investigate energy harvesting on railway bridges. The tuning frequency for the optimal design of cantilever based 3D printed energy harvesters is studied. An analytical model to represent the electromechanical behaviour of the device is presented for the estimation of the energy harvested from train-induced bridge vibrations. A genetic algorithm constrained to geometry and structural integrity is used to solve the optimisation problem. Additive manufacturing by 3D printing of the substructure of the harvester is considered to maximise the design flexibility and energy performance. Optimal device prototypes with PAHT-CF15 substructure are designed for a real bridge in the Madrid-Sevilla High-Speed line. Finally, the performance of energy harvesting is evaluated from in situ experimental data measured by the authors. The results allow quantifying the energy harvested in a time window of three and a half hours and 19 train passages.
Experimental study of the use of ultra-thin plies in quasi-isotropic laminates under cyclic tension after impact
(Asociación Española de Materiales Compuestos (AEMAC), 2024-01) Sandino de Benito, Carlos; Sánchez-Carmona, Serafín; Correa Montoto, Elena; París Carballo, Federico; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Consejería de Economía y Conocimiento, Junta de Andalucía; Ministerio de Universidades; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
In this work, the authors propose an experimental study on the possible improvement of the mechanical behaviour produced by ultra-thin plies in laminates subjected to cyclic loading after impact. More specifically, this work introduces the use of these plies in carbon fibre quasi-isotropic laminates, with the aim of studying the evolution of impact damage under tensile cyclic loads. To this aim, the behaviour of quasi-isotropic laminates consisting of conventional thickness plies is compared with laminates with 90° ultra-thin plies, keeping the same stacking sequence. When considering the same loading level, the damage evolution shows a lower progress and a later failure for the laminates containing ultra-thin plies.
Study of the influence of stacking sequence in the failure of crossply laminates manufactured with ultra-thin plies
(Asociación Española de Materiales Compuestos (AEMAC), 2024-01) Velasco López, María Luisa; Correa Montoto, Elena; Sánchez-Carmona, Serafín; París Carballo, Federico; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Consejería de Economía y Conocimiento, Junta de Andalucía; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
Numerous studies on the use of laminates manufactured with ultra-thin composite laminates have shown the existence of a significant delay in the appearance of damage, a phenomenon known as the Scale Effect. To study the effect that layer thickness may have on the damage mechanisms that appear at higher values of the load, this work analyses whether the use of ultra-thin laminates exhibits a better behaviour in the instants prior to failure and laminate rupture. For this purpose, different laminates have been manufactured with ultrathin thickness material formed by the same number of laminae oriented at 0 and 90 degrees, but with different stacking sequences, distributing the laminae such that the thicknesses of the resulting layers are different. The laminates have been subjected to uniaxial tension up to values close to the ultimate load in order to observe and compare the different damage morphologies that appear in the 90 and 0 degrees layers, using optical microscopy techniques for the observation of the damage. On the other hand, the loads for which the failure of the selected laminates happens have also been compared. The results obtained from this study show different behaviour of the laminates depending on the thickness of their 0 and 90 degrees layers in the moments prior to failure and at the instant when failure occurs.
Behaviour of fibre/matrix interface cracks under biaxial stress state caused by edge effect in carbon/epoxy laminates
(Asociación Española de Materiales Compuestos (AEMAC), 2024-01) Sánchez-Carmona, Serafín; Sandino de Benito, Carlos; Correa Montoto, Elena; Barroso Caro, Alberto; París Carballo, Federico; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla; Consejería de Economía y Conocimiento, Junta de Andalucía; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
A recent study about the ''edge effect'' phenomenon in cross-ply laminates made of ultrathin plies composites has shown the presence of a relevant stress component through the laminate thickness. This fact implies that there is a biaxial stress state in the 90° ply block, which is present both before and after the cyclic loading tests. 4 cross-ply laminates were analysed, only varying the 90° ply block thickness. In each case, the biaxial stress state was obtained, selecting the most detrimental one to analyse the Energy Release Rate (G) with respect to the fibre/matrix interface crack growth. This analysis is performed using a BEM model from a previous study of the authors. An exhaustive microscopic revision is performed both before (only sanded and polished after curing process) and after cyclic testing, corroborating the occurrence of different crack growth of the present longitudinal fibre/matrix interface debonds. In conclusion, the single fibre numerical model using BEM and the experimental microscopic observations shed light on the micromechanical behaviour of the interface cracks which are subjected to a biaxial stress state.

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