arXiv subjects

Federico Bosia

Publications and source records attributed to Federico Bosia.

At least 19 recordsLinked to original sources

arXiv2026

Predictive beam-lattice reduction for higher-order topological modes in a 2D SSH phononic crystal

We develop a mechanically faithful reduced model for a two-dimensional topological phononic crystal composed of rigid square masses connected by slender elastic ligaments. Exploiting Euler Bernoulli beam theory, we derive a Hermitian 12 degree of freedom dynamical matrix that retains in-plane translations, rotations, and ligament eccentricity. This reduction captures effects that are absent from scalar mass spring SSH models while remaining computationally much more tractable and more easily interpretable than full finite element simulations. Dimerizing the ligament widths produces a mechanical 2D SSH lattice with a full band gap and a quantized bulk polarization. The sign of the dimerization controls the transition from trivial to non trivial phases, while ligament eccentricity provides an additional purely geometric mechanism for changing the topology. Ribbon and finite cell calculations predict in gap edge and corner modes, quantified by localization measures and confirmed by finite element simulations. Measurements on 3D printed samples show an evanescent response in the trivial structure and enhanced boundary/corner response in the non trivial structure within the predicted gap. The results provide a validated route for designing topological elastic metamaterials using a continuum informed discrete model rather than either idealized mass spring networks or brute force numerical optimization.

physics.comp-ph↗

arXiv2025

Metamaterials and Fluid Flows

Understanding and controlling the dynamic interactions between fluid flows and solid materials and structures-a field known as fluid-structure interaction -is central not only to established disciplines such as aerospace and naval engineering but also to emerging technologies such as energy harvesting, soft robotics, and biomedical devices. In recent years, the advent of metamaterials-rationally designed composites with properties beyond their constituents, often not found in conventional materials-has provided exciting opportunities for rethinking and redesigning fluid-structure interaction. The premise of engineering the internal structure of materials interfacing with fluid flows is opening a new horizon for precise and effective manipulation and control of coupled fluidic, acoustic, and elastodynamics responses. This review focuses on this relatively unexplored interdisciplinary theme with broad real-world technological significance. Key performance metrics, such as fuel consumption of transport systems, efficiency of renewable energy extraction, mitigation of noise emissions, and resilience to structural fatigue, depend on the control of interactions between flow, acoustic, and vibration mechanisms. Flow control, for example, which spans a wealth of regimes such as laminar, transitional, turbulent, and unsteady separated flows, is highly influenced by the ability to tailor fluid-structure interaction behavior. We survey and discuss theoretical frameworks that describe the interplay between fluids and elastic solids, with a focus on contemporary work and emerging concepts. The paper is organised into three main sections-flow-structure interactions, acoustic-structure interactions, and exotic metamaterial concepts with potential impact on fluid-structure interaction-and concludes with perspectives on current challenges and future directions in this rapidly expanding area of research.

cond-mat.soft↗

arXiv2025

Longitudinal-flexural wave mode conversion via periodically undulated waveguides with constant and graded profiles

Wave mode conversion allows to transform energy from one propagating wave type to another at a boundary where a change in material properties or geometry occurs. Converting longitudinal waves to flexural ones is of particular interest in elasticity due to their significant displacement amplitudes, facilitating detection at the surface for practical applications. Typically, the design of wave conversion devices requires (i) the use of locally resonant structures with a spacing much shorter than the associated wavelengths, or (ii) architected media whose effective properties yield efficient mode conversion at selected frequencies. In both cases, the realization of these devices may incur in fabrication difficulties, thus requiring alternative solutions based on simpler designs that can retain the wave manipulation capabilities of interest. In this paper, we propose the use of single-phase periodically undulated beams to design phononic crystals that achieve wave mode conversion between longitudinal and flexural waves. We derive the corresponding dispersion relations using the plane wave expansion method and demonstrate that the coupling between longitudinal and flexural wave modes can be manipulated using an undulated profile, generating mode veering with inverted group velocities. The wave conversion mechanism is verified both computationally and experimentally, showing good agreement. Our findings indicate a versatile design strategy for phononic crystals with efficient wave conversion property, enabling applications in structural health monitoring, sensing, and non-destructive testing.

physics.app-ph↗

arXiv2023

Elastic wave dispersion in layered media with suture joints: influence of structural hierarchy and viscoelasticity

Suture joints contribute to the exceptional combination of stiffness, strength, toughness and efficient load bearing and transmission of many biological structures like the cranium or ammonite fossil shells. However, their role in the attenuation of vibrations and effect on dynamic loads is less clear. Moreover, the self-similar hierarchical geometry often associated with suture joints renders its treatment with standard numerical approaches computationally prohibitive. To address this problem, this paper investigates the dynamic response of periodic layered media with suture joints using an analytical approach based on material homogenization. A general trapezoidal suture geometry is considered together with the fundamental ingredients of hierarchy and viscoelasticity. The Spectral Element Method and Bloch theorem are used to derive the dispersion relation and band diagram of the system, including propagating and evanescent dispersion modes. A strong influence of the suture morphology and material properties emerges, and the analysis reveals an important advantage of adding hierarchy, i.e. the possibility of simultaneously obtaining wider bandgaps and their shift to higher frequencies. A synergy between hierarchy and structure is also observed, providing superior levels of wave attenuation. These findings suggest a possible design concept for bioinspired devices with efficient and tailorable wave attenuation properties.

physics.gen-ph↗

arXiv2023

Attenuating surface gravity waves by an array of submerged resonators: an experimental study

We report on an experimental study of a device composed by an array of submerged, reversed and periodic cylindrical pendula (resonators), whose objective is the attenuation of surface gravity waves. The idea is inspired by the concept of metamaterials, i.e. engineered structures designed to interact with waves and manipulate their propagation properties. The study is performed in a wave flume where single frequency waves are excited in a wide range of frequencies. We explore various configurations of the device, measuring the transmitted, reflected and dissipated energy of the waves. If the incoming wave frequencies are sufficiently close to the natural frequency of the pendula, we find a considerable wave attenuation effect, driven by viscous dissipative mechanisms. This behaviour is enhanced by the number of resonators in the array. Moreover, the device is also capable of reflecting the energy of selected frequencies of the incoming waves. These frequencies can be predicted by assuming the interactions involving at least three wave modes, including higher harmonics, and are therefore associated with the distance between the resonators. The presented results show promise for the development of a environmentally sustainable device for mitigating waves in coastal zones.

physics.flu-dyn↗

arXiv2023

Source and defect localization in thin elastic plates of arbitrary geometry using eigenmodes

In this paper, we experimentally demonstrate how discrete resonances can be used to image acoustic sources and mechanical changes in thin plates with different boundary shapes. The proposed method uses coupled numerical and experimental data processing, and it only requires the knowledge of the sample geometry (and not its elastic properties). If a limited number of measurement points is available in experiments, the free modes of the plates are not orthogonal from the receivers' point of view, and this induces an artificial coupling in the post-processing of the experimental signals. However, we show that this effect can be corrected using numerical simulations and a mathematical transformation of the antenna geometry. After this correction, imaging of active sources is performed using coherent summation of the elastic field over the natural frequencies of the plates, leading to an unique localization of the sources. Imaging mechanical changes in the two plates, instead, is addressed using incoherent summation over the modes, leading to symmetry problems for the plates. This work experimentally illustrates the spatial resolution, perspectives and limitations in the use of eigenmodes to produce images in complex elastic systems of arbitrary shape and materials.

physics.app-ph↗

arXiv2022

Hierarchical auxetic and isotropic porous medium with extremely negative Poisson's ratio

We propose a novel two-dimensional hierarchical auxetic structure consisting of a porous medium in which a homogeneous matrix includes a rank-two set of cuts characterised by different scales. The six-fold symmetry of the perforations makes the medium isotropic in the plane. Remarkably, the mesoscale interaction between the first- and second-level cuts enables the attainment of a value of the Poisson's ratio close to the minimum reachable limit of -1. The effective properties of the hierarchical auxetic structure are determined numerically, considering both a unit cell with periodic boundary conditions and a finite structure containing a large number of repeating cells. Further, results of the numerical study are validated experimentally on a polymeric specimen with appropriately arranged rank-two cuts, tested under uniaxial tension. We envisage that the proposed hierarchical design can be useful in numerous engineering applications exploiting an extreme auxetic effect

physics.app-ph↗

arXiv2022

Robust substrate anchorages of silk lines with extensible nano-fibres

Living systems are built of multiscale-composites: materials formed of components with different properties that are assembled in complex micro- and nano-structures. Such biological multiscale-composites often show outstanding physical properties that are unachieved by artificial materials. A major scientific goal is thus to understand the assembly processes and the relationship between structure and function in order to reproduce them in a new generation of biomimetic high-performance materials. Here, we tested how the assembly of spider silk nano-fibres (i.e. glue coated 0.5 micron thick fibres produced by so-called piriform glands) into different micro-structures correlates with mechanical performance by empirically and numerically exploring the mechanical behaviour of line anchors in an orb weaver, a hunting spider and two ancient web builders. We demonstrate that the anchors of orb weavers exhibit outstanding mechanical robustness with minimal material use by the indirect attachment of the silk line to the substrate through a soft domain ('bridge'). This principle can be used to design new artificial high-performance attachment systems.

physics.app-ph↗

arXiv2022

Band gap enhancement in periodic frames using hierarchical structures

The quest for novel designs for lightweight phononic crystals and elastic metamaterials with wide lowfrequency band gaps has proven to be a significant challenge in recent years. In this context, lattice-type materials represent a promising solution, providing both lightweight properties and significant possibilities of tailoring mechanical and dynamic properties. Additionally, lattice structures also enable the generation of hierarchical architectures, in which basic constitutive elements with different characteristic length scales can be combined. In this work, we propose 1D- and 2D-periodic phononic crystals made of spatial frames inspired by a spider web-based architecture. Specifically, hierarchical plane structures based on a combination of frames with a variable cross-section are proposed and exploited to open and enhance band gaps with respect to their non-hierarchical counterparts. Our results show that hierarchy is effective in broadening existing band gaps as well as opening new full band gaps in non-hierarchical periodic structures.

physics.app-ph↗

arXiv2022

Correlation between slip precursors and topological length scales at the onset of frictional sliding

Understanding the interplay between concurrent length scales is a fundamental issue in many problems involving friction between sliding interfaces, from tribology to the study of earthquakes and seismic faults. On the one hand, a macroscopic sliding event is preceded by slip precursors with a characteristic propagation length scale. On the other hand, the emergent frictional properties can be modified by surface patterning depending on their geometric length scale. This suggests that macroscopic sliding of structured surfaces is governed by the interplay between the length scale of the slip precursors and those characterizing the geometric features. In this paper, we investigate these aspects by means of numerical simulations using a two-dimensional spring-block model. We discuss the influence of the geometric features on the occurrence and localization of slip precursors, extending the study to interfaces characterized by two geometric length scales. We find that different types of detachment sequences are triggered by specific surface structures, depending on their scales and relation to sliding direction, leading to a macroscopically smooth transition to sliding in the case of hierarchical and/or anisotropic features. These concepts could be exploited in devices switching from static to dynamic sliding, and can contribute to an improvement in the understanding and interpretation of seismic data

physics.app-ph↗

arXiv2022

Design and characterization of cochlea-inspired tonotopic resonators

The cochlea has long been the subject of investigation in various research fields due to its intriguing spiral architecture and unique sensing characteristics. One of its most interesting features is the ability to sense acoustic waves at different spatial locations, based on their frequency content. In this work, we propose a novel design for a tonotopic resonator, based on a cochlea-inspired spiral. The resulting structure was subjected to an optimization process to exhibit out-of-plane vibration modes with mean out-of-plane displacement maxima distributed along its centerline spanning nearly a two-decade frequency range. Numerical simulations are performed to demonstrate the concept, which is also confirmed experimentally on a 3D printed structure. The obtained frequency-dependent distribution is shown to be a viable source of information for the discrimination of signals with various frequency components. The harnessed tonotopic features can be used as a fundamental principle to design structures with applications in areas such as non-destructive testing and vibration attenuation.

physics.app-ph↗

arXiv2021

Experimental and numerical study of the effect of surface patterning on the frictional properties of polymer surfaces

We describe benchmark experiments to evaluate the frictional properties of laser patterned low-density polyethylene as a function of sliding velocity, normal force and humidity. The pattern is a square lattice of square cavities with sub-mm spacing. We find that dynamic friction decreases compared to non-patterned surfaces, since stress concentrations lead to anticipated detachment, and that stick-slip behavior is also affected. Friction increases with humidity, and the onset of stick-slip events occurs in the high humidity regime. Experimental results are compared with numerical simulations of a simplified 2-D spring-block model. A good qualitative agreement can be obtained by introducing a deviation from the linear behavior of the Amontons-Coulomb law with the load, due to a saturation in the effective contact area with pressure. This also leads also to the improvement of the quantitative results of the spring-block model by reducing the discrepancy with the experimental results, indicating the robustness of the adopted simplified approach, which could be adopted to design patterned surfaces with controlled friction properties.

cond-mat.soft↗

arXiv2021

A combined experimental/numerical study on the scaling of impact strength and toughness in composite laminates for ballistic applications

In this paper, the impact behaviour of composite laminates is investigated, and their potential for ballistic protection assessed, as a function of the reinforcing materials and structures for three representative fibre-reinforced epoxy systems involving carbon, glass, or para-aramid fibre reinforcements, respectively. A multiscale coupled experimental/numerical study on the composite material properties is performed, starting from single fibre, to fibre bundles (yarns), to single composite ply, and finally at laminate level. Uniaxial tensile tests on single fibres and fibre bundles are performed, and the results are used as input for non-linear Finite Element Method (FEM) models for tensile and impact simulation on the composite laminates. Mechanical properties and energy dissipation of the single ply and multilayer laminates under quasi-static loading are preliminarily assessed starting from the mechanical properties of the constituents and subsequently verified numerically. FEM simulations of ballistic impact on multilayer armours are then performed, assessing the three different composites, showing good agreement with experimental tests in terms of impact energy absorption capabilities and deformation/failure behaviour. As result, a generalized multiscale version of the well-known Cuniff criterion is provided as a scaling law, which allows to assess the ballistic performance of laminated composites, starting from the tensile mechanical properties of the fibres and fibre bundles and their volume fraction. The presented multiscale coupled experimental-numerical characterization confirms the reliability of the predictions for full-scale laminate properties starting from the individual constituents at the single fibre scale.

physics.app-ph↗

arXiv2021

Attenuating surface gravity waves with mechanical metamaterials

Metamaterials and photonic/phononic crystals have been successfully developed in recent years to achieve advanced wave manipulation and control, both in electromagnetism and mechanics. However, the underlying concepts are yet to be fully applied to the field of fluid dynamics and water waves. Here, we present an example of the interaction of surface gravity waves with a mechanical metamaterial, i.e. periodic underwater oscillating resonators. In particular, we study a device composed by an array of periodic submerged harmonic oscillators whose objective is to absorb wave energy and dissipate it inside the fluid in the form of heat. The study is performed using a state of the art direct numerical simulation of the Navier-Stokes equation in its two-dimensional form with free boundary and moving bodies. We use a Volume of Fluid interface technique for tracking the surface and an Immersed Boundary method for the fluid-structure interaction. We first study the interaction of a monochromatic wave with a single oscillator and then add up to four resonators coupled only fluid-mechanically. We study the efficiency of the device in terms of the total energy dissipation and find that by adding resonators, the dissipation increases in a non trivial way. As expected, a large energy attenuation is achieved when the wave and resonators are characterised by similar frequencies. As the number of resonators is increased, the range of attenuated frequencies also increases. The concept and results presented herein are of relevance for applications in coastal protection.

physics.flu-dyn↗

arXiv2020

Quantum micro-nano devices fabricated in diamond by femtosecond laser and ion irradiation

Diamond has attracted great interest as a quantum technology platform thanks to its optically active nitrogen vacancy center (NV). The NV's ground state spin can be read out optically exhibiting long spin coherence times of about 1 ms even at ambient temperatures. In addition, the energy levels of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platform for efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Diamond photonics enhances optical interaction with NVs, beneficial for both quantum sensing and information. Diamond is also compelling for microfluidic applications due to its outstanding biocompatibility, with sensing functionality provided by NVs. However, it remains a significant challenge to fabricate photonics, NVs and microfluidics in diamond. In this Report, an overview is provided of ion irradiation and femtosecond laser writing, two promising fabrication methods for diamond based quantum technological devices. The unique capabilities of both techniques are described, and the most important fabrication results of color center, optical waveguide and microfluidics in diamond are reported, with an emphasis on integrated devices aiming towards high performance quantum sensors and quantum information systems of tomorrow

physics.optics↗

arXiv2019

A numerical model for the peeling of elastic membranes

The adhesive behaviour of biological attachment structures such as spider web anchorages is usually studied using single or multiple peeling models involving "tapes", i.e. one-dimensional contacts elements. This is an oversimplification for many practical problems, since the actual delamination process requires the modelling of complex two-dimensional adhesive elements. To achieve this, we develop a numerical approach to simulate the detachment of an elastic membrane of finite size from a substrate, using a 3D cohesive law. The model is validated using existing analytical results for simple geometries, and then applied in a series of parametric studies. Results show how the pull-off force can be tuned or optimized by varying different geometrical or mechanical parameters in various loading scenarios, and the length of the detachment boundary, known as the peeling line, emerges as the key factor to maximize adhesion. The approach presented here can allow a better understanding of the mechanical behaviour of biological adhesives with complex geometries or with material anisotropies, highlighting the interaction between the stress distributions at the interface and in the membrane itself.

physics.comp-ph↗

arXiv2019

Competition between delamination and fracture in multiple peeling problems

Adhesive attachment systems consisting of multiple tapes or strands are commonly found in nature, for example in spider web anchorages or in mussel byssal threads, and their structure has been found to be ingeniously architected in order to optimize mechanical properties, in particular to maximize dissipated energy before full detachment. These properties emerge from the complex interplay between mechanical and geometric parameters, including tape stiffness, adhesive energy, attached and detached lengths and peeling angles, which determine the occurrence of three main mechanisms: elastic deformation, interface delamination and tape fracture. In this paper, we introduce a formalism to evaluate the mechanical performance of multiple tape attachments in different parameter ranges, allowing to predict the corresponding detachment behaviour. We also introduce a numerical model to simulate the complex multiple peeling behaviour of complex structures, illustrating its predictions in the case of the staple-pin architecture. We expect the presented formalism and numerical model to provide important tools for the design of bioinspired adhesive systems with tunable or optimized detachment properties.

physics.class-ph↗

arXiv2018

A frequency-preserving and time-invariant metamaterial-based nonlinear acoustic diode

We present the realization of an acoustic diode or rectifier, exploiting symmetry-breaking nonlinear effects like harmonic generation and wave mixing and the filtering capabilities of metamaterials. The essential difference and advantage compared with previous acoustic diode realizations is that the present is simultaneously a time invariant, frequency preserving and switchable device. This allows its application also as an on-off or amplitude-tuning switch. We evaluate its properties by means of a numerical study and demonstrate its feasibility in a preliminary experimental realization. This work may provide new opportunities for the practical realization of structural components with one-way wave propagation properties.

physics.app-ph↗