Reliability design optimisation of classic composite plates using a CUF-based layerwise approach

Uncertainties in the manufacturing process of structures may arise at any moment of the fabrication chain. In the case of composite structures, such uncertainties may appear in the material elastic properties as a result of the microscale features of such material or even from manufacturing flaws, such as misalignments, fibre waviness, etc. [1] when assembling the final product. As a result of these defects, the structural response of the final structure might be compromised. Therefore, a reliability analysis is needed. In this work, a reliability-based design optimization (RBDO) [2] regarding the linearized buckling behavior of a straight-fibre composite laminate is carried out concerning homogeneous material elastic properties variation. In order to perform such analyses, Carrera Unified Formulation (CUF) [3] is used, according to which structural theories with low-order accuracy to layerwise models can be implemented in a hierarchical and unified manner. These analyses are then used to build a surrogate model based on Polynomial Chaos Kriging (PCK) [4], which substitutes the finite element model and thus accelerates the optimization process. The final scope of the work is to show that layerwise models can help to broaden the design space that other structural approaches may have shrunk, while subjected to the manufacturing constraints that the industry has imposed through the years [5]. References [1] A. Pagani, A.R. Sanchez-Majano. Influence of fibre misalingments on buckling performance of variable stiffness composites using layerwise models and random fields. Mechanics of Advanced Materials and Structures 2020. DOI: https://doi.org/10.1080/15376494.2020.1771485 [2] M. Moustapha, B. Sudret. Surrogate-assisted reliability-based design optimization: a survey and a unified modular framework. Structural and Multidisciplinary Optimization 60, 2157–2176 (2019). DOI: 10.1007/s00158-019-02290-y [3] E. Carrera, M. Cinefra, M. Petrolo, E. Zappino. Finite Element Analysis of Structures through Unified Formulation. Wiley & Sons. 2014. ISBN: 978-1-119-94121-7. [4] R. Schobi, S. Marelli, B. Sudret, UQLab user manual – Polynomial chaos Kriging, Report # UQLab-V1.3-109, Chair of Risk, Safety and Uncertainty Quantification, ETH Zurich, Switzerland, 2019 [5] G.H.C. Silva, A.P. do Prado, P.H. Cabral, R. De Breuker, J.K.S. Dillinger. Tailoring of a Composite Regional Jet Wing Using the Slice and Swap Method. Journal of Aircraft, 1–15. (2019) DOI:10.2514/1.c03509

Stochastic stress analysis and failure onset of variable angle tow laminates affected by spatial fibre variations

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 steering of brittle fibres is not flaw-exempt and, in fact, is greatly affected by the printer signature. This manuscript aims to examine the influence of fibre misalignments on the stress and failure index distribution in laminated VAT composites. For doing so, the Carrera Unified Formulation (CUF) is employed to develop layerwise models with unprecedented accuracy. Flaws are introduced at the layer scale by means of stochastic fields and uncertainty analysis is carried out through a Monte Carlo analysis. The random variation (defects) is propagated through the scales and correlated with the stress and failure index distribution. The results show that misalignments greatly affect the in-plane normal stresses, which lately influence fibre tension and compression failure mechanisms

Refined 1D finite elements for thin-walled curved structures

This paper presents numerical results on the static and dynamic analysis of thinwalled, composite structures. The results are obtained via 1D finite elements based on refined beam theories. The Carrera Unified Formulation (CUF) is employed to build the refined theories. In the CUF framework, structural models can be obtained using expansions of the unknown variables along the cross-section of the beam. Any expansion type can be employed; for instance, polynomial, exponential, harmonic, etc.. Moreover, the order of the expansion can be set as an input, and chosen via a convergence analysis. Such features stem from the use of a few fundamental nuclei to obtain the governing equations and the finite element matrices. The formal expressions of the nuclei are independent of the order and the type of the expansion. 1D CUF models can provide 3D-like accuracies with low computational cost. Moreover, nonclassical effects, such as warping, can be dealt with straightforwardly. This paper shows the latest extension of 1D CUF models. Legendre polynomials are employed as expansion functions of the displacement variables. The use of Legendre polynomials allows the parametrization of the cross-section geometry to tackle complex geometries, such as curved boundaries. The Principle of Virtual Displacements (PVD) is employed to obtain the finite element matrices. Various structural configurations are considered, including composite, thin-walled, curved structures. The results are compared with those from literature and 3D finite element models

Update on the treatment of focal segmental glomerulosclerosis in renal transplantation

Focal segmental glomerulosclerosis (FSGS) represents one of the most severe glomerular diseases, with frequent progression to end-stage renal disease and a high rate of recurrence in renal allografts (30%-50%). Recurrent FSGS portends a negative outcome, with the hazard ratio of graft failure being two-fold higher then that of other glomerulonephritis. Two patterns of clinical presentations are observed: Early recurrence, which is characterized by massive proteinuria within hours to days after implantation of the renal graft, and late recurrence, which occurs several months or years after the transplantation. Many clinical conditions have been recognized as risk factors for recurrence, including younger age, rapid progression of the disease to end-stage renal disease on native kidneys, and loss of previous renal allografts due to recurrence. However, much less is known about the incidence and risk factors of the so-called “de novo” type of FSGS, for which sufferers are transplanted patients without disease on native kidneys; but, rapid development of allograft failure is frequently observed. Management of both forms is challenging, and none of the approaches proposed to date have been demonstrated as consistently beneficial or effective. In the present review we report an update on the available therapeutic strategies for FSGS in renal transplantation within the context of a critical overview of the current literature

Top-philic ALP phenomenology at the LHC: the elusive mass-window

We study the LHC phenomenology of an Axion Like Particle (ALP) that couples only derivatively with the top quark at tree level. We inspect the radiatively induced couplings with the SM fermions and (gauge) bosons and the associated production and decay mechanisms of the ALP. We focus on the most challenging mass window that remains open for a top-philic ALP, i.e., the range between tens and hundreds of GeV. Not only ALP production processes but also virtual ALP contributions to final states with top quarks are considered in detail. We show how searches through resonant production, such as ALP production in association with a $t\bar t$ pair, are complementary to precision measurements of $t \bar t$ and $t\bar t t \bar t$ final states, the latter being competitive or even more powerful for a top-philic ALP in this mass window. Finally, we explore the scenario where the top-philic ALP acts as a mediator to a dark-matter sector, resulting in missing energy signatures at the LHC. We find that the LHC constraints from $t \bar t$, $t\bar t t \bar t$ and ALP + jet production, together with those from $t \bar t$ + ALP production, can already exclude a large fraction of the parameter space leading to the correct relic abundance.Comment: 45 pages + appendices, 23 figure

Unraveling late Pennsylvanian brachiopod assemblages from the San Rafael Basin (Argentina): Biostratigraphic implications to southwestern Gondwana

New and previous fossil remains and resulting biostratigraphy of the El Imperial Formation at Arroyo del Imperial, Quebrada de La Horqueta, and Can˜on ´ del Atuel key sections are analyzed, while the faunal relationships among them are clarified. Two diachronnous faunas, the pTS and TSAIII associations, relatives to the TivertoniaStreptorhynchus assemblage are recognized and constrained to early late Bashkirian and Moscovian ages, respectively. These age assignments are supported by statistical analyses and available palynological and radiometric dating. Previous mentions of brachiopods from Arroyo del Imperial and Quebrada de La Horqueta are elucidated with the identification of Buxtonia cf. riojanae (Leanza), Streptorhynchus inaequiornatus Leanza, Spiriferellina? sp., Septosyringothyris (Precosyringothyris) aff. jaguelensis Lech, Septosyringothyris (Precosyringothyris) cf. feruglioi (Amos), Saltospirifer guevarai Cisterna and Archbold and Pericospira sp. A new marine fauna from the upper part of the Can˜on ´ del Atuel section (Cabecera del Can˜on ´ Member) is reported. It includes the brachiopods Argentiella cf. A. stappenbecki Archbold, Cisterna and Sterren, Oehlertella annae (Feruglio), Orbiculoidea saltensis Reed, Calytrixia piersoni Taboada, Coolkilella aredesi Taboada, Costatumulus sp. and Septosyringothyris? sp. A biochronostratigraphic correlation scheme, including key lithostratigraphic units and biozones of central-western Argentina is updated.Fil: Taboada, Arturo Cesar. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales y Ciencias de la Salud - Sede Esquel. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Centro de Investigación Esquel de Montaña y Estepa Patagónica; ArgentinaFil: Pardo, Cristian Adrian. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales y Ciencias de la Salud - Sede Esquel. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Centro de Investigación Esquel de Montaña y Estepa Patagónica; ArgentinaFil: Taboada, Carlos Alberto. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Pagani, María Alejandra. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin

AGOSTINO. VOLERE E POTERE

This contribution reconstructs – with the necessary references to the Manichaean and Pelagian positions – the relationship between will and power in the Augustine’s thought. It focuses on the Book VIII of Confessions, extending to the previous (especially De duabus animabus, De libero arbitrio III) and following (especially De natura et Gratia, De Civitate Dei V and XIV, De Gratia et libero arbitrio) texts, in which the themes of this Book are developed. According to Augustine, the human will, when it is not gathered in itself, is not performing; but even when it is performing, it is unable to carry out what it proposes. This double impotence introduces the theme of original sin and opens up a perspective on the theme of velleitas