Marco Paggi

IMT School for Advanced Studies Lucca · MUSAM Multi-scale Analysis of Materials

To efficiently predict the crack propagation in thin-walled structures, a global–local approach for phase field modeling using large-deformation solid shell finite elements considering the enhanced assumed strain (EAS) and the assumed natural strain (ANS) methods for the alleviation of locking effects is developed in this work. Aiming at tackling t...

Fracture growth in a material is strongly influenced by the presence of inhomogeneities, which deviate crack trajectories from rectilinearity and deeply affect failure. Increasing crack tortuosity is connected to enhancement of fracture toughness, while often a crack may even be stopped when it impinges a void, which releases the stress concentrati...

We present a combined phase field and cohesive zone formulation for hydrogen embrittlement that resolves the polycrystalline microstructure of metals. Unlike previous studies, our deformation-diffusion-fracture modelling framework accounts for hydrogen-microstructure interactions and explicitly captures the interplay between bulk (transgranular) fr...

Thermo-elastic fracture is a matter of important concern for thin-walled structures made of functionally graded materials (FGMs). Based on this practical relevance, a thermodynamically consistent framework is proposed in this investigation for solving the coupled thermo-mechanical phase-field fracture problem in thin-walled structures made of FGMs....

Fracture growth in a material is strongly influenced by the presence of inhomogeneities, which deviate crack trajectories from rectilinearity and deeply affect failure. Increasing crack tortuosity is connected to enhancement of fracture toughness, while often a crack may even be stopped when it impinges a void, which releases the stress concentrati...

The analysis of fracture phenomena of thin-walled structures has been a matter of intensive research in the last decades. These phenomena notably restrict the applicability of slender structures, especially under the influence of temperature. With the aim of achieving a reliable prediction of temperature-driven failures in thin-walled structures, t...

The development of new high-tech products often requires the optimization of structural components having layer-based arrangements. The primary focus of the present study is the analysis of the failure mechanisms that may occur in thin layer-flexible substrate systems: crack propagation through the layers, delamination at interfaces, and mixed-mode...

This article's main scope is the presentation of a computational method for the simulation of contact problems within the finite element method involving complex and rough surfaces. The approach relies on the MPJR (eMbedded Profile for Joint Roughness) interface finite element proposed in [arXiv:1805.07207], which is nominally flat but can embed at...

Robust numerical prediction of crack propagation in heterogeneous media has been a matter of relevant importance in many engineering applications. In this study, a modelling framework for triggering dynamic fracture events in heterogeneous media, like layered materials, with internal finite thickness cohesive interfaces is proposed through the expl...

This article’s main scope is the presentation of a computational method for the simulation of contact problems within the finite element method involving complex and rough surfaces. The approach relies on the MPJR (eMbedded Profile for Joint Roughness) interface finite element proposed in Paggi and Reinoso (2020), which is nominally flat but can em...

Delamination and cracking of matrix/fiber is a common failure phenomena reported in fiber reinforced compos- ite. As complex stress states develop in laminated structures, they are prone to fractures. Therefore, designs with large damage tolerance are currently implemented in most of the industrial sectors. This can be achieved by designing the com...

An extension to the interface finite element with eMbedded Profile for Joint Roughness (MPJR interface finite element) is herein proposed for solving the frictional contact problem between a rigid indenter of any complex shape and an elastic body under generic oblique load histories. The actual shape of the indenter is accounted for as a correction...

Fractional calculus has been proved to be very effective in representing the visco-elastic relaxation response of materials with memory such as polymers. Moreover, in modelling the temperature dependency of the material functions in thermo-visco-elasticity, the standard time–temperature superposition principle is known to be ineffective in most of...

It is well known that humidity and temperature greatly influence the degradation of interfacial adhesion in photovoltaic (PV) modules. Besides, for accurate prediction of the required energy to peel off the different plies of end-of-life PV for recycling, it is also essential to take these factors into account. In this work, a polynomial cohesive z...

An extension to the interface finite element with eMbedded Profile for Joint Roughness (MPJR interface finite element) is herein proposed for solving the frictional contact problem between a rigid indenter of any complex shape and an elastic body under generic oblique load histories. The actual shape of the indenter is accounted for as a correction...

A computational approach that is based on interface finite elements with eMbedded Profiles for Joint Roughness (MPJR) is exploited in order to study the viscoelastic contact problems with any complex shape of the indenting profiles. The MPJR finite elements, previously developed for partial slip contact problems, are herein further generalized in o...

The dynamic behaviour of periodic thermodiffusive multi-layered media excited by harmonic oscillations is studied. In the framework of linear thermodiffusive elasticity, periodic laminates, whose elementary cell is composed by an arbitrary number of layers, are considered. The generalized Floquet-Bloch conditions are imposed, and the universal disp...

With the aim of understanding failure modes in the peeling of silicone-based adhesive joints and, in particular, the occurrence of adhesive or cohesive failure, an experimental campaign has been conducted by considering plastic substrates with different surface roughness. A flexible strip has been bonded onto such substrates using a silicone adhesi...

Failure processes in Laminated Fiber-Reinforced Composites (LFRCs) entail the development and progression of different physical mechanisms and, in particular, the interaction between inter-laminar and intra-laminar cracking. Reliable modeling of such complex scenarios can be achieved by developing robust numerical predictive tools that allow for th...

Fractional calculus has been proved to be very effective in representing the visco-elastic relaxation response of materials with memory such as polymers. Moreover, in modelling the temperature dependency of the material functions in thermo-visco-elasticity, the standard time-temperature superposition principle is known to be ineffective in most of...

A 3-D porous apatite scaffold (B-HA), recently obtained through biomorphic transformation of a natural wood, is investigated on its multi-scale porous structure determining superior mechanical properties and biological behaviour. B-HA shows hierarchical pore architecture with wide aligned channels interconnected with smaller tubules, thus recapitul...

In "Contact Mechanics Perspective of Tribology", J. Greenwood & J. Barber, Müser & Q.J. Wang, J. Luo & J. Krim, K. Nakano & I. Etsion and many other renown experts show to what extent one can understand tribology with macroscopic contact mechanics.

A multi-scale variational-asymptotic homogenization method for periodic microstructured materials in presence of thermoelasticity with periodic spatially dependent one relaxation time is introduced. The asymptotic expansions of the micro-displacement and the micro-temperature fields are rewritten on the transformed Laplace space and expressed as po...

A multiscale asymptotic homogenization method for periodic microstructured materials in presence of thermoelasticity with periodic spatially dependent one relaxation time is introduced. The asymptotic expansions of the micro-displacement and the micro-temperature fields are rewritten on the transformed Laplace space and expressed as power series of...

It is a time to gather stones... The Research Topic (RT) "Contact Mechanics Perspective of Tribology" was planned as a comprehensive overview of recent developments in the areas of contact mechanics and friction. Much has changed in this field in the last few decades. Contact mechanics expanded to qualitatively new fields of application which are a...

The dynamic behaviour of periodic thermodiffusive multi-layered media excited by harmonic oscillations is studied. In the framework of linear thermodiffusive elasticity, periodic laminates, whose elementary cell is composed by an arbitrary number of layers, are considered. The generalized Floquet-Bloch conditions are imposed, and the universal disp...

A computational approach that is based on interface finite elements with eMbedded Profiles for Joint Roughness (MPJR) is exploited in order to study the viscoelastic contact problems with any complex shape of the indenting profiles. The MPJR finite elements, previously developed for partial slip contact problems, are herein further generalized in o...

The present contribution focuses on the effect of adherend surface roughness on the strength of adhesive joints, which are particularly cost-effective and extensively applied in a wide range of industrial applications. However, the reliability of such solutions is a critical concern for the integrity of commercial products. To gain a deeper underst...

A phase field (PF) approximation of fracture for functionally graded materials (FGM) using a diffusive crack approach incorporating the characteristic length scale as a material parameter is herein proposed. A rule of mixture is employed to estimate the material properties, according to the volume fractions of the constituent materials, which have...

Phase-Field (PF) methods of fracture have emerged as powerful modeling tools for triggering fracture events in solids. These numerical techniques efficiently alleviate mesh dependent pathologies and are very suitable for characterizing brittle as well as quasi-brittle fracture in a wide range of engineering materials and structures including fiber...

The FOSS CFD-SPH code SPHERA v.9.0.0 (RSE SpA) is improved to deal with “fluid–solid body” interactions under no-slip conditions and laminar regimes for the simulation of hydrodynamic lubrication. The code is herein validated in relation to a uniform slider bearing (i.e. for a constant lubricant film depth) and a linear slider bearing (i.e. for a f...

With the aim of understanding failure modes in the peeling of silicone-based adhesive joints and, in particular, the occurrence of adhesive or cohesive failure, an experimental campaign has been conducted by considering plastic substrates with different surface roughness. A flexible strip has been bonded onto such substrates using a silicone adhesi...

Phase-field (PF) methods applied to fracture have become attractive and efficient modeling tools to solve complex problems of triggering cracking events in solids from a different signature. These numerical techniques have significantly mitigated the mesh-dependent pathology and are widely applied to brittle, ductile, and even models involving plas...

The phenomenon of arrest of an unstably-growing crack due to a curved weak interface is investigated. The weak interface can produce the deviation of the crack path, trapping the crack at the interface, leading to stable crack growth for certain interface geometries. This idea could be used as a technical solution for a new type of crack arrester,...

The Smoothed Particle Hydrodynamics code SPHERA (RSE SpA) is validated on a laboratory urban dam-break flood. Comparisons with a porous Shallow Water Equations - Finite Volume Method 2D model are also reported. SPHERA provides a performance comparable with the state-of-the-art code, with results closer to the measured values during the most risky f...

A critical analysis of the open data provided by the Italian Civil Protection Centre during phase 1 of Covid-19 epidemic—the so-called Italian lockdown—is herein proposed in relation to four of the most affected Italian regions, namely Lombardy, Reggio Emilia, Valle d’Aosta, and Veneto. A possible bias in the data induced by the extent in the use o...

The present contribution focuses on the effect of adherend surface roughness on the strength of adhesive joints, which are particularly cost-effective and extensively applied in a wide range of industrial applications. However, the reliability of such solutions is a critical concern for the integrity of commercial products. To gain a deeper underst...

The phase field (PF) approach to fracture has emerged as a promising modeling tool that regularizes the variational fracture theory by Griffith via the introduction of a coupled nonlocal damage-like field. In this work, we outline a PF formulation for triggering brittle fracture phenomena in shell structures made of Functionally Graded Materials (F...

In the present work, the evolution of damage in periodic composite materials is investigated through a novel finite element-based multiscale computational approach. The proposed methodology is developed by means of the original combination of asymptotic homogenization with the phase field approach to nonlocal damage. This last is applied at the mac...

SPHERA v.9.0.0 (RSE SpA) is a FOSS CFD-SPH research code validated on the following application fields: floods with transport of solid bodies and bed-load transport; fast landslides and their interactions with water reservoirs; sediment removal from water bodies; fuel sloshing tanks; hydrodynamic lubrication for energy efficiency actions in the ind...

Artificial intelligence is changing perspectives of industries about manufacturing of components, introducing emerging techniques such as additive manufacturing technologies. These techniques can be exploited to manufacture not only precision mechanical components, but also interfaces. In this context, we investigate the use of artificial intellige...

Transverse intralaminar cracks in layers with perpendicular orientation referred to the main loading direction have a significant affection on the apparent ultimate strength of the corresponding composite laminate. This effect stems from the fact that such transverse cracks generally promote the occurrence of other failure mechanisms leading to the...

Computational models for the simulation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic evolution would be extremely useful to support authorities in designing healthcare policies and lockdown measures to contain its impact on public health and economy. In Italy, the devised forecasts have been mostly based on a pure da...

Although the composition of polymer matrix is only ≈5% by weight, the presence of polymer as an interlayer between the brittle aragonite bricks significantly enhances the toughness characteristics of the natural nacre. In this study, the mechanics of nacre-like brick-mortar structures is investigated through numerical simulations. The shear stress...

A novel multi-scale finite element formulation for contact mechanics between nominally smooth but microscopically rough surfaces is herein proposed. The approach integrates the interface finite element method (FEM) for modelling interface interactions at the macro-scale with a boundary element method (BEM) for the solution of the contact problem at...

This chapter provides a self-consistent introduction to computational methods for the solution of contact problems between bodies separated by rough interfaces. Both frictional and frictionless contact problems are examined. The mathematical formulation of the boundary element method is presented first, with details on the possible algorithmic impl...

Interface phenomena at the micro- and nanoscales are of paramount importance in nature and technology. Real surfaces present roughness over multiple scales, and understanding the role of roughness in surface physics (heat and electric transfer, hydrophobic properties), surface chemistry (chemical reactions) and tribology (stress transfer, adhesion,...

The progressive damage analysis of fiber-reinforced composite materials is a challenging task, especially when complicated cracking scenarios arise due to the onset and progression of several damage mechanisms. From a modeling point of view, a particularly complex failure scenario is the interaction between intralaminar and interlaminar cracks. Thi...

The nature of failure in long fiber-reinforced composites is strongly affected by damage at the micro-scale. The presence of different phases at different length scales leads to a significant complexity in the failure progression. At the micro-scale, the complexity is due to the presence of different points of initiation for damage and the presence...

Accelerated ageing tests of photovoltaic laminates are requested by the IEC standards for quality control, which require the assessment of the electrical power losses after a prescribed amount of temperature and/or humidity cycles inside a climatic chamber (thermal cycling, humidity freeze, and damp heat tests). Since electric damage is measured on...

A novel multi-scale finite element formulation for contact mechanics between nominally smooth but microscopically rough surfaces is herein proposed. The approach integrates the interface finite element method (FEM) for modelling interface interactions at the macro-scale with a boundary element method (BEM) for the solution of the contact problem at...

Rough and textured surfaces are of paramount importance for lubrication, both in nature and in technology. While surface roughness relevantly influences both friction and wear, artificial surface texturing improves the performance of slider bearings as an energy efficiency action. The simulation of hydrodynamic lubrication by taking into account co...

A 3-D porous apatite scaffold (B-HA), recently obtained through biomorphic transformation of a natural wood, is investigated on its multi-scale porous structure determining superior biological and mechanical behaviour. B-HA shows a hierarchically organized architecture with wide aligned channels interconnected with smaller tubules, thus recapitulat...

The phenomenon of arrest of an unstably-growing crack due to a curved weak interface is investigated. The weak interface can produce the deviation of the crack path, trapping the crack at the interface, leading to stable crack growth for certain interface geometries. This evidence could be exploited as a technical solution for a new type of crack a...

The FOSS CFD-SPH code SPHERA v.9.0.0 (RSE SpA) is empowered to deal with fluid-solid body interactions under no-slip conditions and laminar regimes for the simulation of hydrodynamic lubrication. The code is herein validated in relation to a uniform slider bearing (i.e., for a constant lubricant film depth) and a linear slider bearing (i.e., for a...

In an attempt to mimic the outstanding mechanical properties of wood and bone, a 3D heterogeneous chemistry approach has been used in a biomorphic transformation process (in which sintering is avoided) to fabricate ceramics from rattan wood, preserving its hierarchical fibrous microstructure. The resulting material (called biomorphic apatite [BA] h...

Announcement of the new Research Topic "Contact mechanics perspective of tribology" edited by: Irina Goryacheva, Marco Paggi & Valentin L. Popov: https://www.frontiersin.org/research-topics/11677/contact-mechanics-perspective-of-tribology

Delamination cracks in composite laminates may originate from manufacturing defects, low-energy impacts, and many other causes. Once present, a delamination crack may propagate due to local buckling producing high interlaminar stresses at the crack front [1]. To investigate this phenomenon, many authors have suggested carrying out four-point bendin...

In the present work, the evolution of damage in periodic composite materials is investigated through a novel finite element-based multiscale computational approach. The methodology is developed by means of the original combination of homogenization methods with the phase field approach of fracture. This last is applied at the macroscale level on th...

The properties of nanoscale interphase significantly influence the mechanics of load transfer and hence the macroscopic behavior of fiber-reinforced composites. Herein, we present a theoretical framework to study the mechanics of stress transfer through both homogeneous and inhomogeneous interphases in a curved-fiber pull-out test and analyse the s...

Backsheet blistering in photovoltaic modules is frequently reported but not yet thoroughly described. Visual inspection only identifies the presence of bubbles, while physical mechanisms leading to their occurrence need further theoretical investigation. To evaluate the effect of external (temperature, humidity) and internal (manufacturing defects)...

In this work, the phase field (PF) approach for brittle fracture in the bulk coupled with the cohesive zone model (CZM) for pre-existing interfaces is exploited for the simulation of fracture of thin films on compliant substrates, which are structural configurations of extensive use in many engineering systems such as protecting layers for vessels,...

Rock fracture in geo-materials is a complex phenomenon due to its intrinsic characteristics and the potential external loading conditions. As a result, these materials can experience intricate fracture patterns endowing various cracking phenomena such as: branching, coalescence, shielding, and amplification, among many others. In this article, we p...

A non-local dynamic homogenization technique for the analysis of wave propagation in viscoelastic heterogeneous materials with a periodic microstructure is herein proposed. The asymptotic expansion of the micro-displacement field in the transformed Laplace domain allows obtaining, from the expression of the micro-scale field equations, a set of rec...

Additive manufacturing technologies are a key point of the current era of Industry 4.0, promoting the production of mechanical components via the addition of subsequent layers of material. Then, they may be also used to produce surfaces tailored to achieve a desired mechanical contact response. In this work, we develop a method to prototype profile...