Artículos (Mecánica de Medios Continuos y Teoría de Estructuras)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11397

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Enhancing the matrix-fiber bond in ultra-high-performance fiber-reinforced concrete using a high performance plasticizer. Impact on the flowability, physical and mechanical properties
(Elsevier, 2025) Ruiz Martínez, Jaime D.; Ríos Jiménez, José David; Pérez-Soriano, Eva María; Cifuentes Bulté, Héctor; Leiva Fernández, Carlos; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP972: Mecánica de Materiales y Estructuras; Universidad de Sevilla. TEP118: Ingeniería de los Transportes; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP142: Ingeniería de Residuos
One of the main problems in the use of ultra-high-performance fiber-reinforced concrete (UHPFRC) with steel fibers is low flowability. The addition of 2,3,4,5,6-Pentahydroxycaproic acid sodium salt (SPS) in small amounts (0.05, 0.1 and 0.15 %wt of the cement content) can significantly increase the flowability and setting time. The effects on porosity, matrix chemical composition and fiber-matrix interaction were examined, as well as its influence on strength. Improving the flowability, pores larger than 50 μm show a significant decrease, while those smaller than 0.1 μm show a significant increase. According to the results of thermo-gravimetric analysis, the production of ettringite with finer grains and staggered symbiosis improves the pore structure of the UHPFRC matrix. An improvement of the adhesion of the steel fibers to the matrix was determined by stereomicroscope images, showing evidence of a relationship between SPS dosage and the expanded concrete area surrounding the fiber. The flexural and compressive strength increased by 10 % and 8 %, respectively, when the plasticizer/cement ratio was 0.15 %.
Efect of nano silicon nitride on the microstructural characteristics and mechanical properties of ultra‑high‑performance steel fber reinforced concrete
(Springer Nature, 2025) Ruiz Martínez, Jaime D.; Ríos Jiménez, José David; Pérez-Soriano, Eva María; Cifuentes-Bulté, Héctor; Leiva Fernández, Carlos; Universidad de Sevilla. Departamento de Ingeniería Química y Ambiental; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP142: Ingeniería de Residuos; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales; Universidad de Sevilla. TEP972: Mecánica de Materiales y Estructuras
This study investigates the incorporation of an innovative nano-reinforcement, nano silicon nitride (NSIN), to enhance the workability and mechanical performance of ultra-high-performance fber reinforced concrete. The addition of NSIN at dosages of 0.25, 0.5, 0.75, and 1.5 wt% of cement was analyzed to evaluate its impact on the distribution and interaction between steel fbers and the cementitious matrix. Experimental analyses, including thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were conducted to establish a relationship between the microstructural modifcations, fber-matrix interactions, and the resulting mechanical behavior. The fndings revealed that NSIN increased workability and extended setting time, enabling improved steel fber dispersion and interaction
Wear and subsurface stress evolution in tractive rolling contact
(Elsevier, 2025-05-15) Juliá Lerma, Javier Miguel; Rodríguez de Tembleque Solano, Luis; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
Wear phenomenon is inherent to tractive rolling contact problems e.g., in rolling bearings or in rail–wheel interaction. It takes place in the sliding regions of the rolling contact area, and it accumulates as particles from the rolling bodies cross the contact region. Wear modifies the solids’ surface, the contact tractions, the subsurface stresses, and the tangential forces transmitted between the rolling solids, which are fundamental contact variables in sectors such as rolling fatigue or vehicle system dynamics. Thus, ignoring wear in tractive rolling contact analysis could lead to underestimations of bearing fatigue lives or inaccurate lateral guiding forces in multibody vehicle models. This work presents a robust SAM-based formulation on rolling contact to study how wear, contact tractions, resultant rolling contact-forces, and surface and subsurface stresses evolve with the number of revolutions. For the first time, subsurface stress distributions are computed as a function of revolutions under orthotropic friction and wear conditions, highlighting the influence of tribological axes orientation and wear evolution on stress and force reactions. After validating the proposed formulation, several numerical examples are presented to show how considering orthotropic friction and wear laws impacts stress distributions and resultant rolling contact forces. These findings could provide important insights into the role of wear in tractive rolling contact for applications in engineering and industrial design.
Effect of thickness-to-radius ratio on the impact response of fabric-reinforced composite shells
(Elsevier, 2025) 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; Fundação para a Ciência e a Tecnologia. Portugal; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
This study analyses the effect of thickness-to-radius (t/R) ratio on the dynamic response of fabric-reinforced composite shells subjected to low-velocity impact loads using 3D finite element models validated by experimental results. Focus is given to the t/R ratio's influence on energy dissipation and damage modes. For thick-walled shells (t/R > 0.05) the peak force and contact time increases as the curvature decreses (i.e., with a larger radius), while the maximum displacement decreases. On the other hand, thin-walled shells (t/R < 0.05) exhibit lower peak forces, larger displacements, and longer contact times as the curvature decreases. This transition indicates the existence of a critical point around the radius of 50 mm (t/R = 0.05). The main mechanism for energy dissipation in thick-walled shells is intralaminar damage, and its contribution decreases with increasing radius, whereas for thin-walled shells, friction and delamination determine the absorption of impact energy. In terms of damage propagation patterns, thick-walled shells show localized intra- and interlaminar damage, while thin-walled shells evidence a cross-like intralaminar pattern with more extensive delamination.
Review of the matched asymptotic approach of the coupled criterion
(Académie des Sciences, 2025) Jiménez Alfaro, Sara; García García, Israel; Doitrand, Aurélien; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
Matched Asymptotics is a powerful mathematical technique with broad applicability in various engineering fields. One of its key uses is in Fracture Mechanics, where it provides accurate approximations in the vicinity of the crack tip with low computational complexity. This method can be seamlessly integrated with the Coupled Criterion (CC), which enables the prediction of crack nucleation and propagation in brittle materials. Hence, this paper deeply explains how the MA technique can be applied together with the CC in the context of Fracture Mechanics, providing a detailed literature review of the advances made in the last decade.
A dialogue between Finite Fracture Mechanics and Phase Field approaches to fracture for predicting crack nucleation at the microscale
(Springer, 2025-01-20) Jiménez Alfaro, Sara; Leguillon, Dominique; Maurini, Corrado; Reinoso Cuevas, José Antonio; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP963: Ingeniería de Estructuras y Materiales
Unraveling the material behavior at the microscale is one of the challenges of this century, demanding progress in experimental and computational strategies. Among the latter, two approaches are commonly applied for predicting crack nucleation. The Coupled Criterion (CC) and the Phase Field (PF) model, both depending on a material length parameter. In brittle materials at the macroscale, this parameter is significantly smaller than the specimen size. However, when the scale decreases, this material length might approach the structural dimensions. In this context, a comprehensive comparison between the two models is conducted, changing the ratio between the material length parameter and the dimensions of the specimen. Results indicate that when this ratio is sufficiently small predictions from both models coincide, otherwise both the CC and the PF model predict different results. Despite their differences, an agreement with experiments reported in the literature have been observed.
Phase field modeling of anisotropic silicon crystalline cracking in 3D thin-walled photovoltaic laminates
(Springer, 2025-01) Liu, Zeng; Lenarda, Pietro; Reinoso Cuevas, José Antonio; Paggi, Marco; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España
A novel computational framework integrating the phase field approach with the solid shell formulation at finite deformation is proposed to model the anisotropic fracture of silicon solar cells in the thin-walled photovoltaic laminates. To alleviate the locking effects, both the enhanced assumed strain and assumed natural strain methods are incorporated in the solid shell element formulation. Aiming at tackling the poor convergence performance of standard Newton schemes, the efficient and robust quasi-Newton scheme is adopted for the solution of phase field modeling with enhanced shell formulation in a monolithic manner. Due to fracture anisotropy of the brittle silicon solar cells, the second-order structural tensor that is defined by the normal of preferential crack plane is introduced into the crack energy density function in the phase field modeling. On the other hand, to efficiently predict the crack growth of silicon solar cells, a global–local approach in the 3D setting proposed in the previous work is adopted here for the fracture modeling. In this approach, both mechanical deformation and phase field fracture are accounted for at the local model, while only mechanical deformation is addressed at the global level. At each time step, the solution of the global model is used to drive the local model, which corresponds to the one-way coupling in line with experimental evidence that the silicon cell cracking has negligible influence on the stiffness of photovoltaic modules. The capability of the modeling framework is demonstrated through numerical simulation of silicon solar cell cracking in the photovoltaic modules when subjected to different loading cases.
The influence of thermo-electromechanical coupling on the performance of lead-free BNT-PDMS piezoelectric composites
(IOP Publishing, 2024) Akshayveer; Buroni Cuneo, Federico Carlos; Melnik, Roderick; Rodríguez de Tembleque Solano, Luis; Sáez Pérez, Andrés; Singh, Sundeep; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
In recent times, there have been notable advancements in haptic technology, particularly in screens found on mobile phones, laptops, light-emitting diode (LED) screens, and control panels. However, it is essential to note that the progress in high-temperature haptic applications is still in the developmental phase. Due to their complex phase and domain structures, lead-free piezoelectric materials such as Bi0.5Na0.5TiO3 (BNT)-based haptic technology behave differently at high temperatures than in ambient conditions. Therefore, it is essential to investigate the aspects of thermal management and thermal stability, as temperature plays a vital role in the phase and domain transition of BNT material. A two-dimensional thermo-electromechanical model has been proposed in this study to analyze the thermal stability of the BNT-PDMS composite by analyzing the impact of temperature on effective electromechanical properties and mechanical and electric field parameters. However, the thermo-electromechanical modelling of the BNT-PDMS composite examines the macroscopic effects of the applied thermal field on mechanical and electric field parameters, as phase change and microdomain dynamics are not considered in this model. This study analyzes the impact of thermo-electromechanical coupling on the performance of the BNT-PDMS composite compared to conventional electromechanical coupling. The results predicted a significant improvement in piezoelectric response compared to electromechanical coupling due to the increased thermoelectric effect in the absence of phase change and microdomain switching for temperature boundary conditions below depolarization temperature (Td ∼ 200◦C for pure BNT material).
On the (lack of) representativeness of quasi-static variational fracture models for unstable crack propagation
(Elsevier, 2024-05) Chao Correas, Arturo; Reinoso Cuevas, José Antonio; Cornetti, Pietro; Corrado, Mauro; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TEP963: Ingeniería de Estructuras y Materiales
The present work is devoted to prove that unstable crack propagation events do not comply with quasi-static hypotheses and thus should be modelled by dynamic approaches. Comprehensive supporting evidence is provided on the basis of three different analyses conducted on multi-ligament unstable fracture conditions, including a simplified Spring-Mass model, detailed quasi-static and dynamic Phase Field fracture models, and bespoke experiments with 3D printed specimens. The obtained results unequivocally show that neglecting the inertial effects can lead to unsafe predictions in the presence of energetic barriers for the development of fracture. Likewise, quasi-static Phase Field fracture models are proven to yield crack patterns that disagree with the experimental evidence because they overlook the progressive diffusion of the mechanical information within the continuum. Moreover, the inability of quasi-static approaches to follow unstable crack propagation is shown to weaken the crucial irreversibility condition of fracture. Overall, these experimentally backed insights should be gravely reckoned with, for they are not exclusive to Phase Field fracture models but common to (almost) any variational approach to fracture, inter alia Cohesive Zone Models or Continuum Damage Mechanics.
Evaluating failure modes through energy dissipation mechanisms in hybrid composites under bending loads
(Elsevier, 2025-03) Parente, J.M.; Ferreira, Luis Miguel Marques; Reis, Paulo Nobre Balbis; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Fundação para a Ciência e a Tecnologia. Portugal; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Universidad de Sevilla. TEP131: Grupo de Elasticidad y Resistencia de Materiales
Understanding the bending behaviour of composite materials is essential for effective design, particularly with the increasing use of complex components with multiple bends. Carbon fibres are often preferred in such applications due to their superior tensile properties; however, given their limited compressive performance, hybridization with glass fibres is commonly used. In this context, this study analyses the energy contributions of intralaminar and interlaminar damage mechanisms leading to failure in hybrid carbon/glass fabric-reinforced laminates under bending loads. Different hybridization ratios and configurations, specifically the positioning of glass and carbon fabric reinforcements relative to the load application, are evaluated experimentally and numerically. The experimental results show that the bending performance of hybrid laminates falls between those of non-hybrid carbon (8C) and glass (8G) laminates, with a clear dependence on the hybridisation ratio. When glass fibres are positioned in the compression region, the hybrid laminates exhibit slightly higher force and displacement values. Notably, the 3G/5C configuration (glass on the compression side) achieves a force and a displacement of 255.1 N and 4.23 mm, respectively, representing increases of approximately 5.9% and 13.1% compared to the 5C/3G configuration, which reaches 240.9 N and 3.74 mm. Numerical models show a good agreement with the experimental data, with force errors predominantly within ±5.3% and displacement errors within ±6.8%. Non-hybrid configurations demonstrate a more predictable damage progression, whereas hybrid laminates introduce variability due to differences in fiber type and placement, influencing overall energy dissipation and structural performance. Additionally, the energy analysis reveals that intralaminar damage is the dominant energy dissipation mechanism, followed by delamination and friction.
Evolutionary game theory‑based finite element model updating of a moveable cable‑stayed footbridge
(Springer Science, 2024-11) Jiménez Alonso, Javier Fernando; Ereiz, Suzana; Duvnjak, Ivan; Caetano, Elsa; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Ciencia, Innovación y Universidad (MICIU). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Universidad de Sevilla. TEP245: Ingeniería de las Estructuras
Evolutionary game theory allows determining directly the solution of the maximum likelihood finite element model updating problem via the transformation of a bi-objective optimization problem into a game theory problem. The formulation of the updating problem as a game avoids the computation of the Pareto front and the solution of the subsequent decision-making problem, the selection of the best solution among the elements of the Pareto front. For this purpose, each term of the bi-objective function is considered as a player that interacts collaboratively or non-collaboratively with the other player during the game. One of the main advantages of this method is that a different global optimization algorithm can be associated with each player. In this manner, a higher performance in the solution of the updating problem is expected via the linking between each term of the objective function (a player) and the algorithm considered for its minimization. In this study, this advantage is analysed in detail. For this purpose, the finite element model updating process of a real footbridge, the Viana do Castelo footbridge, has been considered as a benchmark. As global optimization algorithms, different nature-inspired computational algorithms have been considered. The updating problem has been solved using two different methods: (i) the linking of a conventional bi-objective optimization method together with a decision-making method; and (ii) an evolutionary game theory method. As a result, a higher performance of the game theory method has been highlighted. Additionally, the influence of the considered optimization algorithm in the updating process has been noted
Effect of 3D-Printed Hexagonal Honeycomb Core Density of PLAWood Based Subjected to Low-Velocity Impact
(Society of Sugar Palm Development and Industry Malaysia, 2024-12) Ainin, F. Nur; Azaman, M.D.; Majid, M.S. Abdul; Ridzuan, M.J.M.; Ferreira, Luis Miguel Marques; Coelho, Carlos A.C.P.; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras
Additive manufacturing (AM) technology has become the preferred method for fabricating lightweight sandwich composite structures, due to its ability to produce complex designs rapidly. However, these structures are susceptible to performance decline and potential damage, especially under impact loading in engineering applications. This study investigates the low-velocity impact characteristics of 3D-printed hexagonal honeycomb cores made from wood-filled polylactic acid (PLA) with unit cell sizes of 6, 8, and 10 mm. Energy absorption and failure mechanisms were assessed through drop-weight impact testing at an energy level of 11 J, with results analyzed using a stereo microscope. The findings demonstrate that unit cell size significantly impacts the performance of sandwich composite structures. Smaller unit cells increase core density, leading to enhanced energy absorption capabilities. The medium-density 8 mm unit cell is identified as the optimal structure for lightweight materials, offering efficient energy absorption and intermediate failure modes. While lighter than the high-density 6 mm unit cell, the 8 mm unit cell absorbs a comparable amount of energy (8 mm: 9.22 J, 6 mm: 9.61 J). Furthermore, this medium-density cell outperforms the low-density 10 mm unit cell, which absorbs only 7.44 J, due to its intermediate stiffness that better resists substantial deformation compared to the lower-density structure.
Effect of moderate temperatures on compressive strength of ultra-high-performance concrete: A microstructural analysis
(Elsevier, 2021-02) Suescum-Morales, David; Ríos Jiménez, José David; Martínez de la Concha, Antonio; Cifuentes-Bulté, Héctor; Jiménez Romero, José Ramón; Fernández Rodríguez, José María; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Junta de Andalucía; Ministerio de Educación, Cultura y Deporte (MECD). España; Ministerio de Economía y Competitividad (MINECO). España; Universidad de Sevilla. TEP972: Mecánica de materiales y estructuras
Concrete with two types of steel fibres and a polypropylene fibre prevented spalling and preserved the compressive strength at 300 °C, which makes these concretes suitable for long-term applications up to 300 °C, such as for steam collectors or thermal energy storage systems. The compressive strength behaviour of three types of ultra-high-performance fibre-reinforced concrete manufactured with the same matrix was investigated. For this purpose, a complete characterisation of all the raw materials and the three types of fibres used was performed. The morphology of all concrete mixtures at room temperature was analysed using scanning electron microscopy–energy-dispersive X-ray spectroscopy. From the results, it was ascertained that the steel fibres and coarse siliceous aggregates were not in contact (being separated by ≥3.41 μm) and were surrounded by the binder (of ≥1 μm in thickness) for all the mixtures studied. Rosenhahnite and/or quartz Dauphiné-twinned phases improved the compressive strength (as determined by X-ray diffraction).
Longitudinal fibre/matrix debonds in CFRP ultra-thin plies: T-T cyclic testing and numerical prediction
(Elsevier, 2025-03) Sánchez-Carmona, Serafín; Sandino de Benito, Carlos; Correa Montoto, Elena; Velasco López, María Luisa; Barroso Caro, Alberto; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Universidad de Sevilla; Junta de Andalucía; Ministerio de Ciencia, Innovación y Universidades (MICINN). España
The edge effect phenomenon in cross-ply laminates made of ultra-thin (UT) 90º plies produces a relevant stress component through the laminate thickness that could lead to the generation of longitudinal debonds (parallel to the loading direction) in the 90° ply block. In this study, specimens from a carbon-epoxy laminate made of conventional 0º and UT 90º ply blocks are inspected after the curing process in order to find longitudinal debonds. The debonds growth is also monitored during a later T-T cyclic testing campaign. The experimental results are compared with the predictions obtained from a BEM model showing a good agreement. Finally, the use of an inverse procedure combining both experimental and numerical analyses leads to the estimation of GIc of the fibre/matrix interface.
Interaction between fibres in the transverse damage in composites
(Elsevier, 2020-11) Velasco López, María Luisa; Correa Montoto, Elena; París Carballo, Federico; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Educación, Cultura y Deporte (MECD). España
A micromechanical study is carried out taking the initial expected damage that is manifested in a composite laminate by the debonding between the fibres and matrix in the 90° lamina as a reference. Questions such as the influence in the appearance of damage of the inter-fibre distance and the orientation of the fibres with respect to the loading direction are studied. Additionally, the effect of the presence of damage at a secondary fibre in the subsequent appearance of further debonding is also analysed. Finally, the conclusions reached are supported by experimental evidence obtained by testing [0,90n]S laminates.
BEM multiscale modelling involving micromechanical damage in fibrous composites
(Elsevier, 2018-08) Velasco López, María Luisa; Graciani Díaz, Enrique; Távara Mendoza, Luis Arístides; Correa Montoto, Elena; París Carballo, Federico; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Educación, Cultura y Deporte (MECD). España
Composite laminates are materials where different scales are required for the understanding of the damage and for the calculation of structures made of these materials. The appearance of ultra thin plies of composites has opened the possibility of delaying the onset of damage, which at a first stage appears at a micromechanical level, debondings in between fibre and matrix in the weakest lamina of the laminate. A multiscale BEM model is developed in the present paper with the final purpose of being able to study the effect that the relative size of the laminas of the laminate plays in the appearance of this initial damage. The model presents many difficulties derived from the different scales involved in it and from the non-linear nature of the problem under study. The approach followed involves the solution of the whole problem, with the different scales involved in it, at once. The solution obtained is checked with another already obtained with a much simpler model. The multiscale model developed has been proved to be very efficient, accurate and robust, having been applied to simulate the first stages of damage in the light of the scale effect that is trying to be studied.
Microscopical observations of inter-fibre failure under tension
(Elsevier, 2018-02-08) Correa Montoto, Elena; Valverde, María Inmaculada; Velasco López, María Luisa; París Carballo, Federico; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Educación, Cultura y Deporte (MECD). España
The numerical study of the inter-fibre failure at micromechanical level predicts the appearance of different stages in the development of this damage mechanism; these studies have also allowed the main features of each stage (such as the interfacial debond length and the kinking angle) to be identified. The development of experimental studies aiming to check the relevance of the aforementioned numerical results is crucial. Based on this, this research focused on the tensile test under different loading levels of specimens manufactured from carbon-epoxy cross-ply symmetrical laminates. The microscopic observation of the 90° layers leads to the analysis of the appearance of the transverse cracks as a function of the load, the identification of the previously numerically predicted stages of the mechanism of damage, the measurement of key parameters and the evaluation of the influence of nearby fibres. A clear connection between the numerical and experimental results has been found.
The scale effect in composites: An explanation physically based on the different mechanisms of damage involved in failure
(Elsevier, 2021-02-01) París Carballo, Federico; Velasco López, María Luisa; Correa Montoto, Elena; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Educación, Cultura y Deporte (MECD). España
The strength of a lamina of a laminate was considered from almost the very beginning of the application of composites as a value depending on the lamina thickness. This was generically called scale effect, the value of the stress at the appearance of first damage in a lamina being identified as the in situ strength. The ultra-thin plies have allowed this first damage, typically transverse cracks in the 90-degree laminas, to be delayed. This study presents a completely physically based explanation of the scale effect in composites based on the key identification of two different failure mechanisms in the 90-degree lamina of a [0,90n]S laminate (here called progressive and explosive) that are triggered as a function of the morphology of the laminate. Their characterization is based on energy concepts and does not require either properties of difficult interpretations or fitting parameters. The study extends from plies of conventional thickness to ultra-thin plies. BEM models have been performed, correlating the predictions with experimental microscopic observations. Developing a physically based explanation of the scale effect is the first step towards identifying the parameters involved in the failure initiation. Once identified, these parameters can be measured.
Interface crack model using finite fracture mechanics applied to the double pull-push shear test
(Elsevier, 2020-04) Muñoz-Reja Moreno, María del Mar; Cornetti, Pietro; Távara Mendoza, Luis Arístides; Mantic, Vladislav; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Junta de Andalucía; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Universidad de Sevilla
An analytical procedure predicting a debond (interface crack) onset and growth in an adhesive joint between two beams or plates is developed and applied to a specific configuration often used in reinforcement tests in civil engineering. The procedure is based on Timoshenko beam theory and Linear Elastic-(Perfectly) Brittle Interface Model (LEBIM) combined with the Coupled Criterion of the Finite Fracture Mechanics (CC-FFM) for mixed-mode fracture. First, a sixth order differential equation in the shear stresses along the adhesive layer is deduced and solved, leading to closed form expressions for both shear and normal stresses in the adhesive. Then, the critical value of the applied load necessary to produce debonding is predicted by coupling a stress and an energy condition based on: (i) the stress distribution produced in the interface before the debond onset and (ii) the energy released during the debonding process along the interface. Although the developed procedure can be applied to several types of joints with different geometries, materials and loads (e.g., double lap joint tests including adherents made of steel or composites), herein it is applied to the double pull-push shear test where the debond onset and growth between a Carbon Fibre Reinforced Polymer (CFRP) laminate and a concrete block occurs. For such a case, the debond is produced under predominant fracture mode II; nevertheless, it is shown that relevant normal (peeling) stresses associated to mode I may appear as well. A comparison of the present solution with a previous one by the shear-lag model is provided as well.
A numerical implementation of the Coupled Criterion of Finite Fracture Mechanics for elastic interfaces
(Elsevier, 2020-08) Muñoz-Reja Moreno, María del Mar; Távara Mendoza, Luis Arístides; Mantic, Vladislav; Cornetti, Pietro; Universidad de Sevilla. Departamento de Mecánica de Medios Continuos y Teoría de Estructuras; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Junta de Andalucía; Universidad de Sevilla
A new numerical procedure for predicting interface failures between solids is developed. The procedure is based on the Linear Elastic-(Perfectly) Brittle Interface Model (LEBIM) combined with the Coupled Criterion of the Finite Fracture Mechanics (CCFFM). Although in the present investigation this procedure is implemented in a 2D BEM code, a general pseudocode is devised allowing its implementation in any BEM or FEM code. The pull-push shear test is used as a benchmark problem, where the fracture mode II is dominant. Nevertheless, the present procedure can tackle a debond growth occurring under any fracture mode mixity. The pull-push problem is chosen since it allows us to check the obtained numerical results against an available analytical solution based on a beam model. Additionally, the numerical results are compared with some experimental data from literature. Furthermore, an inverse analysis is applied to obtain the interface strength and fracture parameters that the model needs.

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