Alfonso Pagani

Polytechnic University of Turin | polito · DIMEAS - Department of Mechanical and Aerospace

Constructing cruise-ship hull is complex and requires precise metalwork, welding and assembly. Early anomaly detection and correction are vital for cost and time management. This paper presents a novel statistical quality control (SQC) methodology for monitoring the panel line in cruise-ship shipyards, i.e., one of the initial manufacturing worksho...

This paper presents a multi-dimensional variable-kinematics finite element model for nonlinear static analyses of structures with complex geometries. The approach incorporates higher-order beam models and classical solid finite elements in a unified framework, enabling refined modeling of complex geometries. The finite element procedure proposed fo...

The advent of Automated Fiber Placement (AFP) in aerospace composites lay-up and manufacturing has allowed orientations to vary along pre-defined curved directions rather than being forced to remain constant within the lamina. These composites are called Variable Angle Tow (VAT) or Variable Stiffness Composites (VSC). Despite the enhancements in me...

This work focuses on deriving guidelines for choosing structural theories for composite shells using Convolutional Neural Networks (CNN). The Axiomatic/Asymptotic Method (AAM) is used to evaluate higher-order structural theories' accuracy and computational efficiency based on polynomial expansions. AAM exploits the Carrera Unified Formulation to de...

This work proposes a higher‐order unified shell finite element for the analysis of cylinders made of compressible and nearly incompressible hyperelastic materials. The nonlinear governing equations are derived employing the Carrera unified formulation (CUF), thanks to which it is possible to build shell elements with the capability to capture three...

In this work, high-order beam (1D) finite element models for the modal analysis of structures made of compressible and nearly-incompressible hyperelastic soft materials are presented in the well-established framework of Carrera Unified Formulation (CUF). In this investigation, the modal behavior of soft structures subjected to progressively increas...

This work proposes a displacement-based finite element model for large strain analysis of isotropic compressible and nearly-incompressible hyperelastic materials. Constitutive law is written in terms of invariants of the right Cauchy-Green tensor; coupled and decoupled formulations of strain energy functions are presented, whereas a penalty functio...

This paper proposes a high-order two-dimensional (2D) finite element model for the analysis of isotropic, nearly incompressible hyperelastic material structures based on a decoupled Neo–Hookean strain energy function. The model is based on the Carrera Unified Formulation (CUF), which allows to automatically implement different kinematics by using a...

This work proposed the use of the Carrera Unified Formulation (CUF) for the vibration and buckling analysis of structures subjected to thermal loads. In detail, the variation of natural frequencies for progressively large thermal loads is investigated. Here, particular attention is focused on the study of buckling thermal loads as degenerate cases...

This work analyses the stochastic response of fibre and matrix scale stresses of Variable Angle Tow (VAT) laminates affected by multiscale uncertainty defects. The aim is to evaluate the influence of the innermost constituents on the overall structural response via an accurate mechanical characterization of both macro- and microscales. The Carrera...

This study examines a new approach to facilitate the convergence of upcoming user-subroutines UMAT when the secant material matrix is applied rather than the conventional tangent (also known as Jacobian) material matrix. This algorithm makes use of the viscous regularization technique to stabilize the numerical solution of softening material models...

This work introduces the use of convolutional neural network (CNN) in combination with advanced structural theories for the damage detection of multi-component and composite structures. Well-established component-wise (CW) models based on the Carrera Unified Formulation (CUF) are developed first to demonstrate the effect of localized damages on the...

In macroscopic applications, the production of graphene foam (GF) can be an attractive way to utilize the combined advantages of graphene sheets and porous materials. The porosity level significantly affects mechanical and thermal properties by changing the specific surface area. In this study, a multi-scale method is used to calculate the coeffici...

This paper discusses the change of the natural frequencies and the corresponding mode shapes of an isotropic metallic curved panel subjected to combined internal pressure and axial compression. Tensor calculus is employed to devise the differential operator matrices of the geometrical relation in an orthogonal curvilinear reference system. In the f...

In this study, the tensile nonlinear responses of composite laminates with ±θns and ±θn/0s layups are investigated. An analytical model that integrates the progressive failure, shear nonlinearity, fiber rotation, and fragmentation is established to characterize the nonlinear tensile behavior. A nonlinear factor is used to describe the shear nonline...

In this paper, theories of structures based on hierarchical Jacobi expansions are explored for the static analysis of multilayered beams, plates and shells. They belong to the family of classical orthogonal polynomials. This expansion is employed in the framework of the Carrera Unified Formulation (CUF), which allows to generate finite element stif...

This article investigates the dynamic nonlinear response of three-dimensional structures using variable-kinematics finite beam elements obtained with the Carrera Unified Formulation. The formalism enables one to consider the three-dimensional form of displacement–strain relations and constitutive law. The deformation mechanisms and the associated c...

The present work proposes a new approach for conducting thermo-elastic micromechanical analysis. It relies on the use of high-order and geometrically accurate beam finite elements to model the microstructures. The governing equations of the micromechanics models involving the unit cell concept are derived through the Mechanics of Structure Genome (...

The thermal buckling behavior of metallic and laminated beams/plates is investigated using a linearized stability analysis. By selecting different reference frames, two distinct types of 3 D stability equations can be generated using total and updated Lagrangian formulations (TLF and ULF). Various beam theory kinematics can be obtained within the f...

This paper presents the numerical damage analysis of concrete structures using higher-order beam theories based on Carrera Unified Formulation (CUF). The concrete constitutive relation is modeled using continuum damage mechanics based on a modified Mazars concrete damage model, in which both the tensile and compressive softening behaviors are regul...

The purpose of this work is to propose an innovative global/local approach for the failure onset analysis of deployable composite thin and ultrathin structures. The adoption of this technique allows for overcoming the weaknesses related to the commercial calculation codes, which make use of three-dimensional finite elements to capture the local str...

In the recent years, machine learning algorithms have been widely employed for structural health monitoring applications. As an example, Artificial Neural Networks (ANN) could be useful in giving a precise and complete mapping of damage distribution in a structure, including low-intensity or localized defects, which could be difficult to detect via...

This work intends to present a novel numerical approach for studying the vibration behaviours of variable angle tow (VAT) composite structures in their quasi-static nonlinear equilibrium states. This methodology is able to predict the buckling load, to investigate the natural frequencies variation for progressively higher loads, and to provide a me...

This paper presents the analysis of free vibration and stress state of steel–concrete composite beams, using high-order theories and closed-form solutions based on Carrera unified formulation (CUF). The governing differential equations are formulated in terms of fundamental nuclei via CUF and the longitudinal differential problem is solved analytic...

In this work, randomly three-dimensional graphene foam (RGF) is synthesized from the chemical reduction of graphene oxide solution in the self-assembly method. RGF/epoxy composite is then obtained by the RTM method. Tensile testing highlights the effect of RGF drying percentage on the composite and shows a 138% and 48% increase in the Young modulus...

In this paper, the use of the node-dependent kinematics concept for the geometrical nonlinear analysis of composite one-dimensional structures is proposed With the present approach, the kinematics can be independent in each element node. Therefore the theory of structures changes continuously over the structural domain, describing remarkable cross-...

The present work provides a numerical model for carrying out virtual Vibration Correlation Technique (VCT) for computing the buckling load, identifying the natural frequencies variation with progressive higher applied load, and providing an efficient means for the verification of the experimental VCT results. The presented nonlinear approach is bas...

View Video Presentation: https://doi.org/10.2514/6.2022-0633.vid As with every manufactured part, composite structures are affected by manufacturing defects. Indeed, these flaws may arise at any stage of the fabrication chain and are present at the different scales of the composite material. For instance, mesoscale flaws, such as waviness and misal...

View Video Presentation: https://doi.org/10.2514/6.2022-0534.vid Combining Carrera Unified Formulation (CUF) with vibration correlaton technique (VCT), this paper discusses the change of the natural frequencies and the relevant modal shapes of an isotropic metallic cylindrical shell subjected to combined internal pessure and axial compression. Tens...

Based on the Carrera unified formulation (CUF) and first-invariant hyperelasticity, this work proposes a displacement-based high order one-dimensional (1 D) finite element model for the geometrical and physical nonlinear analysis of isotropic, slightly compressible soft material structures. Different strain energy functions are considered and they...

This paper proposes an equivalent single-layer approach for modeling laminated structures, where the number layers to be considered as a single one is chosen a priori by the user. Lagrange points are set to locate and, eventually, join equivalent single-layer and layer-wise tenchiques by imposing displacement continuity in the thickness direction....

This work investigates quasi‐static crack propagation in specimens made of brittle materials by combining local and non‐local elasticity models. The portion of the domain where the failure initiates and then propagates is modelled via three‐dimensional bond‐based peridynamics. On the other hand, the remaining regions of the structure are analyzed w...

The employment of nondestructive techniques in aerospace industries is rising thanks to advances in technologies and analysis. This part of the aerospace testing industry is essential to design and validate the new structures’ methodology and safety. Therefore, robust and reliable nondestructive methods have been extensively studied for decades in...

New concepts of lightweight components are conceived nowadays thanks to the advances in the manufacture of composite structures. For instance, mature technologies such as Automatic Fibre Placement (AFP) are employed in the fabrication of structural parts where fibres are steered along curvilinear paths, namely variable angle tow (VAT), which can en...

The present work deals with the free vibration behavior of the variable stiffness composite laminates (VSCLs) featured by spatially varying fibre orientation angles via novel quasi-three-dimensional solutions. The Carrera Unified Formulation (CUF) is employed to construct such novel models, where cross-section kinematics are described with the impr...

Novel manufacturing techniques that have arisen during the last decades have permitted to improve both the manufacturing quality and performance of laminates parts. Despite these improvements, such manufactured parts are not flaw-exempt, since uncertainty in the fabrication processes and in the material properties are still present. At the same tim...

In the aerospace industry, machine learning techniques are becoming more and more important for Structural Health Monitoring (SHM). In fact, they could be useful in giving a precise and complete mapping of damage distribution in a structure, including low-intensities or local defects, which cannot be detected via traditional tests. In this work, fe...

The structural analysis of ultra-lightweight flexible shells and membranes may require the adoption of complex nonlinear strain-displacement relations. These may be approximated and simplified in some circumstances, e.g., in the case of moderately large displacements and rotations, in some others may be not. In this paper, the effectiveness of vari...

This article investigates the large deflection and post-buckling of composite plates by employing the Carrera Unified Formulation (CUF). As a consequence, the geometrically nonlinear governing equations and the relevant incremental equations are derived in terms of fundamental nuclei, which are invariant of the theory approximation order. By using...

The structural analysis of ultra-lightweight flexible shells and membranes may require the adoption of complex nonlinear strain-displacement relations. These may be approximated and simplified in some circumstances, e.g., in the case of moderately large displacements and rotations, in some others may be not. In this paper, the effectiveness of vari...

A reasonable boundary condition for the meso-scale finite element (FE) simulation of textile composites is necessary for model validation against experiments, which is sometimes over-simplified for saving computation time. This paper examines the influence of boundary conditions on the global stress–strain response and deformation pattern, as well...

Multilayer perceptrons are utilized in this work for vibration-based damage detection of multi-component aerospace structures. A back-propagation algorithm is utilized along with Monte Carlo simulations and advanced structural theories for training Artificial Neural Networks (ANN’s), which are able to detect and classify local damages in structures...

It is well known that fabrication processes inevitably lead to defects in the manufactured components. However, thanks to the new capabilities of the manufacturing procedures that have emerged during the last decades, the number of imperfections has diminished while numerical models can describe the ground truth designs. Even so, a variety of defec...

This paper shows some important results from a test campaign conducted on the Dardo Aspect, a wet-laminate full-composite very-light airplane (VLA). Both static and dynamic experimental analyses are carried out. All the results and methodologies utilized in this paper take into account compliance with certification requirements. Particular attentio...

In this study, the unified formulation of a full geometrically nonlinear refined plate theory in a total Lagrangian approach is developed to study the post-buckling and large-deflection analysis of sandwich functionally graded (FG) plate with FG porous (FGP) core. The plate has three layers so that the upper and lower layers are FG and the middle l...

This work deals with highly flexible laminated shell structures. The main focus is to provide an advanced model for the accurate prediction of the interlaminar three-dimensional stress state of shells subjected to large displacements/rotations, buckling, and snap-through phenomena. In this context, a two-dimensional shell finite element based on th...

With the rapid development of engineering constructions, especially transportation facilities, the structural models for the simulation of large-scale structures shall be eventually enhanced for predicting the complete three-dimensional stress and strain fields in reinforced concrete-made components. This paper proposes a component-wise approach fo...

The present paper investigates the 3 D free vibration behavior of curved metallic and composite beams via a novel beam theory. The refined beam theory is constructed within the framework of the Carrera Unified Formulation (CUF), which expands 3 D displacement fields as 1 D generalized displacement unknowns over the cross-section. As a novelty, a se...

The geometrical nonlinear effects caused by large displacements and rotations over the cross section of composite thin-walled structures are investigated in this work. The geometrical nonlinear equations are solved within the finite element method framework, adopting the Newton–Raphson scheme and an arc-length method. Inherently, to investigate cro...

This article investigates the large deflection and post-buckling of composite plates by employing the Carrera Unified Formulation (CUF). As a consequence, the geometrically nonlinear governing equations and the relevant incremental equations are derived in terms of fundamental nuclei, which are invariant of the theory approximation order. By using...

This article investigates the large deflection and post-buckling of composite plates by employing the Carrera Unified Formulation (CUF). As a consequence, the geometrically nonlinear governing equations and the relevant incremental equations are derived in terms of fundamental nuclei, which are invariant of the theory approximation order. By using...

In the framework of finite elements (FEs) applications, this paper proposes the use of the node-dependent kinematics (NDK) concept to the large deflection and post-buckling analysis of thin-walled metallic one-dimensional (1D) structures. Thin-walled structures could easily exhibit local phenomena which would require refinement of the kinematics in...

This work focuses on the study of composite metamaterials to be employed as possible lightweight insulation systems for noise and vibrations. In particular, the dispersion relations are derived by applying the Bloch-Floquet theory to the unit cell of the periodic microstructure. Advanced beam finite elements based on Carrera Unified Formulation are...

This work proposes an alternative approach for the nonlinear analysis of 2D, thin-walled lattice structures. The method makes use of the well-established Carrera Unified Formulation (CUF) for the implementation of high order 1D finite elements, which lay along the thickness direction. In this manner, the accuracy of the mathematical model does not...

This research work deals with the buckling load prediction of reinforced laminated composite panels of aeronautical interest. Being subjected to pure compression, these panels are characterized by stable post-buckling. Thus, the vibration correlation technique (VCT) is utilized herein as an effective nondestructive means to extrapolate critical loa...

By making use of high order shell models, the present work discusses frequency and mode change of thin structures subjected to large displacements and rotations. The models are implemented in the domain of the well-established Carrera Unified Formulation (CUF) and employ the full Green-Lagrange strain tensor, in a total Lagrangian scenario. In this...

The usage of printed composites in the aerospace industry has been steadily increasing over the last years. Especially, 3D printers and automatic fibre placement machines have allowed the introduction of Variable Angle Tow (VAT) composites, which theoretically offer greater tailoring capabilities than classic composite laminates. Nevertheless, the...

This paper deals with the evaluation of time response analyses of typical aerospace metallic structures. Attention is focussed on detailed stress state distributions over time by using the Carrera Unified Formulation (CUF) for modeling thin-walled reinforced shell structures. In detail, the already established component-wise (CW) approach is extend...

This paper presents advanced-kinematics beam models to compute the dispersion characteristics of one-dimensional guides. High-order functions are used to interpolate the primary variables above the waveguide cross-section and along its axis. Taylor- and Lagrange-type bi-dimensional expansions are employed to describe the section deformation, while...

The present paper presents the evaluation of three-dimensional (3D) stress distributions of shell structures in the large displacement and rotation fields. The proposed geometrical nonlinear model is based on a combination of the Carrera Unified Formulation (CUF) and the Finite Element Method (FEM). Besides, a Newton-Raphson linearization scheme is...

The present work investigates the possibility of reducing the strain/stress concentrations in a open-hole plate using localized 3D printed carbon fiber reinforcements. Several reinforcement strategies have been investigated exploiting the capabilities of a recent additive manufacturing process, the carbon filament fabrication, that allows continuou...

In this work, the effect of the fiber orientation on the mechanical response of variable angle tow (VAT) panels is investigated. A computationally efficient high-order one-dimensional model, derived under the framework of the Carrera unified formulation (CUF), is used. In detail, a layerwise approach is adopted to predict the complex phenomena that...

Peridynamics is a non‐local theory which has been successfully applied to solid mechanics and crack propagation problems over the last decade. This methodology, however,may lead to large computational calculations which can soon become intractable for many problems of practical interest. In this context, a technique to couple –in a global/local sen...

This work wants to investigate the soundproofing level of passive acoustic metamaterials made of Melamine Foam and cylindrical Aluminum inclusions. Latest research shows promising acoustical possibilities on controlling certain frequencies, varying their geometry or material configuration. Typically, acoustic metamaterials are plates with inclusion...

Additive manufacturing brought to the emergence of a new class of fiber-reinforced materials; namely, the Variable Angle Tow (VAT) composites. Automated fiber placement machines allow the fibers to be relaxed along curvilinear paths within the lamina. In theory, the designer can conceive VAT structures with unexplored capabilities and tailor materi...

This paper presents the free vibration and static analysis of composite box beam using refined beam theory. The structural model based on one-dimensional (1D) is derived in the Carrera Unified Formulation (CUF) framework. The principle of virtual displacement has been used along with CUF to formulate the finite element arrays in the terms of fundam...

The present paper aims at studying composite cambered structures, tracking the seminar work “Rotating Blade Vibration Analysis Using Shells” presented by Leissa in Journal of Engineering for Power, in 1982, devoted to homogeneous metallic blades. A refined unidimensional (1D) formulation is here implemented to overcome the limitations of classical...

This research work deals with the analysis of elastic shell structures in the large displacement and rotation field adopting one-dimensional (1D) and two-dimensional (2D) unified models. Namely, higher order beam and shell theories accounting for geometrical nonlinearities are formulated by employing a unified framework based on the Carrera unified...

The nonlinear mechanical response of highly flexible plates and shells has always been of primary importance due to the widespread applications of these structural elements in many advanced engineering fields. In this study, the Carrera Unified Formulation (CUF) is used in a total Lagrangian framework to analyze the large-deflection and post-buckli...

An advanced modeling technique for hygro-mechanical analyses has been discussed in the present work. A three-dimensional closed-form solution of the diffusion equation has been developed and used to evaluate the time evolution of the moisture concentration in a composite coupon. A refined kinematic one-dimensional model, derived in the framework of...

In this work, a unified formulation of full geometrically nonlinear refined shell theory is developed for the accurate analysis of highly flexible shell structures. The tensor calculus is utilized to explicitly derive the linear and nonlinear differential operator matrices of the geometrical relation in the orthogonal parallel curvilinear coordinat...

Shear and membrane locking phenomena are fundamental issues of shell finite element models. A family of refined shell elements for laminated structures has been developed in the framework of Carrera Unified Formulation, including hierarchical elements based on higher-order Legendre polynomial expansions. These hierarchical elements were reported to...