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The modern polycrystalline composite materials have a complex internal structure consisting of different phases and interfaces with random distribution. Relevant examples are Al2O3/ZrO2, i.e. alumina/zirconia composites, widely used as structural materials with applications ranging from aerospace to bio-engineering. Depending on the phases content and on the grain size a broad range of material characteristics, among which elastic constants, can be obtained. With the aim of characterizing this class of materials, we exploit a numerical Fast Statistical Homogenization Procedure (FSHP) in order to both estimate the size of the Representative Volume Elements (RVE) and the effective elastic properties, assuming a linear elastic material behaviour. The 2-D analyses are performed considering a microstructure inspired by images of real portions of the Al2O3/ZrO2 composite obtained from a scanning electron microscope. The recent Virtual Element Method is used in combination with the FSHP approach to numerically solve boundary value problems. Different volume contents of phases are considered ranging from pure Alumina to pure zirconia. The results are useful to reliably characterize such materials in the elastic range taking into account the role played by random distribution of grains.

The modern polycrystalline composite materials have a complex internal structure consisting of different phases and interfaces with random distribution. Relevant examples are Al2O3/ZrO2, i.e. alumina/zirconia composites, widely used as structural materials with applications ranging from aerospace to bio-engineering. Depending on the phases content and on the grain size a broad range of material characteristics, among which elastic constants, can be obtained. With the aim of characterizing this class of materials, we exploit a numerical Fast Statistical Homogenization Procedure (FSHP) in order to both estimate the size of the Representative Volume Elements (RVE) and the effective elastic properties, assuming a linear elastic material behaviour. The 2-D analyses are performed considering a microstructure inspired by images of real portions of the Al2O3/ZrO2 composite obtained from a scanning electron microscope. The recent Virtual Element Method is used in combination with the FSHP approach to numerically solve boundary value problems. Different volume contents of phases are considered ranging from pure Alumina to pure zirconia. The results are useful to reliably characterize such materials in the elastic range taking into account the role played by random distribution of grains.

Silicon carbide foam is a promising material for high-temperature use because it has excellent thermal shock resistance and strength, low thermal conductivity, and excellent chemical resistance. Up till now SiC foam was analyzed under quasi-static compression and 4and 3-point bending. This paper attempts for the first time to numerically analyze the SiC foam properties under impact conditions. Using the peridynamical approach it was possible to describe damage initiation, its dynamical growth, and the final fragmentation of the foam. The major conclusions resulting from the analysis are that for high impact velocities damage initiates much earlier compared to low-velocity impact, and the modes of failure are qualitatively different., �������������������� ������������ �������������� ���������������� �������������������������� �������������������� ������ �������������������������� �� ���������������� �������������� ��������������������, ������������������ ���������������� �������������� ������������������������������, ��������������������, �������������������� �������������������� �� ������������ ����������������������������������. ���������������� ���������������������� �������������� �������������� ������������������ �� ���������������� ������ �������������������������������� ������������. �� ������������ ������������ �������������� ���������������������� �������������� �������������������� ������������������������ ���������������������� �������������� �������������� �� ���������������� ���������������� ��������������������. �� ������������ ���������������������������������� �������������� �������������� �������������������� �� ���������������� ����������������������, �� ���������� ������������������������ ������������������. �������������������� ������������������������ ����������������, ������ ������ �������������� ������������������ ���������������� ���������������������� ���������������������� ������������������ ���������������������� ������������, ������ ������ ������������������������������ ����������������������, ������������ ������������ �������������������� ���������� ������������������������ ��������������.

А survey of recent developments in the dynamic analysis of sandwich panels with face sheet-to-core debonding is presented. The finite element method within the ABAQUSTM code is utilized. The emphasis is directed to the procedures used to elaborate linear and non-linear models and to predict dynamic response of the sandwich panels. Recently developed models are presented, which can be applied for structural health monitoring algorithms of real-scale sandwich panels. First, various popular theories of intact sandwich panels are briefly mentioned and a model is proposed to effectively analyse the modal dynamics of debonded and damaged (due to impact) sandwich panels. The influence of debonding size, form and location, and number of such damage on the modal characteristics of sandwich panels are shown. For nonlinear analysis, models based on implicit and explicit time integration schemes are presented and dynamic response gained with those models are discussed. Finally, questions related to debonding progression at the face sheet-core interface when dynamic loading continues with time are briefly highlighted.

A three-dimensional modelling of free vibrations and static response of functionally graded material (FGM) sandwich plates is presented. Natural frequencies and associated mode shapes as well as displacements and stresses are determined by using the finite element method within the ABAQUSTM code. The three-dimensional (3-D) brick graded finite element is programmed and incorporated into the code via the user-defined material subroutine UMAT. The results of modal and static analyses are demonstrated for square metal-ceramic functionally graded simply supported plates with a power-law through-the-thickness variation of the volume fraction of the ceramic constituent. The through-the-thickness distribution of effective material properties at a point are defined based on the Mori-Tanaka scheme. First, exact values of displacements, stresses and natural frequencies available for FGM sandwich plates in the literature are used to verify the performance and estimate the accuracy of the developed 3-D graded finite element. Then, parametric studies are carried out for the frequency analysis by varying the volume fraction profile and value of the ceramic volume fraction.

The paper relates to a numerical analysis of the damage process of interface inside the WC/Co composite microstructure under tensile load by the finite element method. The focus is on comparing two modelling techniques for the damage process of interface material: flat (2-D) modelling and three-dimensional (3-D) modelling of RVEs. The damage process of metallic interface inside the Co composite is described by XFEM (eXtended Finite Element Method), based on a cohesive traction-separation law. The applied numerical tool is the commercial ABAQUS® package, where the non-linear problem is solved by the Newton-Raphson method. The use of 3-D modelling to describe the failure of WC/Co composite metallic interface enabled investigation of the damage process, starting from the moment of damage initiation to the total loss of rigidity of interface elements in a vast area of the examined microstructure.

Dezinformacja jest narzędziem propagandy, mającym na celu fałszowanie rzeczywistości, której zniekształcony obraz ma wpłynąć na odbiorcę i podejmowane przez niego decyzje. Choć nie jest to zjawisko nowe, to w czasach nieograniczonego dostępu do informacji, których treści nie są możliwe do zweryfikowania, jest to proceder szczególnie niebezpieczny. Użytkownicy portali społecznościowych swoją aktywnością dowiedli, że za pomocą dostępnych im środków takich jak memy internetowe, trolling czy astroturfing, mogą wpłynąć na losy nie tylko swoje i swoich narodów, ale zmienić układ sił politycznych na świecie., Colloquium, Tom 11 Nr 3 (2019): Colloquium

A virtual testing of double cantilever beam interlaminar fracture toughness sandwich specimens under different types of dynamic loads and loading rates is considered. The nonlinear dynamic response of those sandwich specimens being fractured during the test is numerically examined using the two-dimensional finite element model within the ABAQUSTM code. The interaction integral method is exploited to extract the dynamic stress intensity factor. Cohesive elements allocated along the face/core interface are used to simulate the dynamic fracturing of the specimens.

Numerical simulations of dynamic fracture behaviour of a double cantilever sandwich beam subjected to uneven bending moments in plane conditions are carried out using the dynamic finite element analyses with the ABAQUSTM code. The strain energy release rate was evaluated by means of the finite element model developed within the two-dimensional (2-D) linear elastodynamic theory. This demonstrates the capability and the reliability of the finite element modelling as an extremely useful numerical tool for solving dynamic fracture mechanics problems. Also, the dynamic behaviour of fracture parameters and interface crack progression is discussed.

The paper presents an interfacial crack problem adopted for studying fracture toughness and debonding tolerance of sandwich composite materials. A specific example of the fracture sandwich specimens such as a double cantilever sandwich beam subjected to uneven bending moments (DCB-UBM) is considered. A finite element modelling of this test method is carried out using the ABAQUS™ code. Atwo-dimensional (2-D) model has been developed to highlight the distribution of stress and displacement fields and to calculate the energy release rate (ERR) and the phase angle at the interface crack between two dissimilar orthotropic materials. The J − integral approach built-in ABAQUS code and the crack surface displacement method programmed as an add-on subroutine within the Matlab® environment are used for computing those fracture parameters. The influence of different moment ratios on the near crack tip stress state, the ERR, and phase angle fracture parameters is estimated. Представлено проблему міжфазної тріщини, за допомогою якої вивчаються в’язкість руйнування та стійкість до відшарування у тришарових композиційних матеріалах. Розглянуто конкретний приклад тришарового зразка на руйнування – двохконсольна тришарова балка, яка навантажена згинальними моментами. Скінчено елементне моделювання цього тесту здійснюється за допомогою програми ABAQUS™. Двовимірна модель була розроблена для виявлення розподілу полів напружень та переміщень, а також для розрахунку швидкості вивільнення енергії руйнування та фазового кута міжфазної тріщини поміж двома різними ортотропними матеріалами. J − інтеграл підхід, який є вбудованою опцією у ABAQUS, та метод відносних зміщень на поверхнях тріщини, який запрограмований у середовищі Matlab® окремою програмою, використовуються для обчислення цих параметрів руйнування. Оцінюється вплив різних співвідношень згинальних моментів на напружений стан в околі вершини тріщини, швидкості вивільнення енергії руйнування і фазовий кут.

A survey of recent developments in the dynamic analysis of sandwich panels with face sheet-to-core debonding is presented. The finite element method within the ABAQUS™ code is utilized. The emphasis is directed to the procedures used to elaborate linear and nonlinear models and to predict dynamic response of the sandwich panels. Recently developed models are presented, which can be applied for structural health monitoring algorithms of real-scale sandwich panels. First, various popular theories of intact sandwich panels are briefly mentioned and a model is proposed to effectively analyse the modal dynamics of debonded and damaged (due to impact) sandwich panels. The influences of debonding size, form, and location and number of such damage incidents on the modal characteristics of sandwich panels are shown. For nonlinear analysis, models based on implicit and explicit time integration schemes are presented and dynamic responses gained with those models are discussed. Finally, questions related to debonding progression at the face sheet-core interface when dynamic loading continues with time are briefly highlighted.

vol. 16(3) (2017) 095-102, In this paper the application of the Extended Finite Element Method (XFEM) to anticipate change of the behaviour of composite with complex internal structure after use of the admixtures was presented. The response to mechanical loadings of bent beams made of hydraulically bonded mixture with rubber admixture was considered. The impact of the rubber granulate on the value of fracture energy was analysed. Moreover, the influence of an interfacial transmission zone quality on the achieved effect was assessed. Calculations were conducted by means of the muli-scale numerical model which was built in ABAQUS finite element method environment. The results derived indicate beneficial effect of rubber granulate on fracture energy of hydraulically bonded mixture.

Zusammenfassung Die menschliche Hautoberfläche enthält beträchtliche Mengen unterschiedlicher Lipide. Sie werden entweder in tieferen Hautschichten synthetisiert und wandern im Zuge der Hautdifferenzierung/Desquamation nach oben (stratum corneum lipide), oder entstehen im Inneren von Talgdrüsen und werden auf der Hautoberfläche ausgeschieden. Zusammen kann die Gesamtheit aller Hautoberflächenlipide als Hautlipidom bezeichnet werden. Ein besseres Verständnis der Variabilität von Hautoberflächenlipiden ist aus zweierlei Gründen das Ziel dieser Arbeit. Die erste Motivation ist ein besseres Verständnis der Hautbiologie an sich. Als wichtiger Bestandteil der Epidermis definieren Hautoberflächenlipide bestimmte Aspekte der Hautmikroanatomie und –physiologie und determinieren zentrale Hautparameter. Die zweite Motivation ist die Erlangung der Fähigkeit ein krankes Hautlipidom erkennen zu können. Dazu muss man wissen wie ein gesundes Hautlipidom variieren kann. Die Zusammensetzung des Hautlipidomes unterliegt erheblichen Schwankungen. Lipide sind das Produkt mehrerer komplexer, miteinander verbundener Synthesewege des Stoffwechesl. Als solche können ihre Mengen auf Prozesse im menschlichen Körper reagieren. Lipidschwankungen können besonders ausgeprägt sein, wenn sie im Zuge einer Hautkrankheit, als ethologischer Faktor oder als Folge auftreten, und damit Barriereeigenschaften der Haut beeinflussen. Aber mutmaßlich gibt es auch einen Schwankungsbereich, der als physiologisch einzuordnen wäre. Zur Vermessung der Hautlipidomzusammensetzung und –variabilität haben wir eine Technologie entwickelt und validiert, die der quantitativen, Hochdurchsatz-Shotgun-Massenspektrometire von Tape-stripping Oberhautproben basiert. Sie ermöglicht die Quantifizierung von 16 Lipidklassen bis runter auf Mengen individueller molekularer Lipidspezies, und ist dabei reproduzierbar und hochdurchsatzfähig. Mit dieser Technologie haben wir die bis heute umfangreichste Hautlipidom-Studie unter Einbeziehung von 268 menschlicher Oberhautproben durchgeführt. Wir haben den Zusammenhang zwischen Tiefe der Probenentnahme und der Zusammensetzung der Hautlipide, die Lipidomvariabilität an 14 unterschiedlichen anatomischen Loci, sowie die Populationsvariabilität des Hautlipidoms innerhalb von 104 Probanden untersucht.:The physiological lipidome of human epidermis Contents Abbreviations III Introduction 1 Architecture of the human shell 4 Measuring skin lipid composition 6 Skin sampling 6 Lipid extraction 9 Lipid identification 10 Lipid quantification 14 The design of this study 16 Material and methods 18 Method development and validation 18 Sampling development 18 Establishment of sample extraction and robotic handling 19 Establishment of mass spectrometric lipid identification 20 Establishment of lipid quantification 21 Skin lipidomic study 22 Sampling preparation 22 Standard sampling via tape stripping 23 Sampling via sequential tape-stripping 25 Lipid extraction 25 MS data acquisition 26 Lipid identification and data processing 27 Results 29 Method development and validation 29 Skin sampling via tape-stripping 29 Lipid extraction 31 Lipid identification 31 Lipid quantification 36 Skin lipidomic study results 38 Vertical skin surface lipid profile 38 Anatomical skin surface lipid variability 43 Inter-individual skin surface lipid variability 46 Discussion 50 Method development and validation 50 Skin sampling via tape-stripping 50 Lipid extraction 52 Lipid identification 53 Lipid quantification 55 Physiological lipid composition and variability 56 Lipidome variability vs sampling depth 56 Intra-individual lipidome variability 58 Inter-individual lipidome variability 59 General discussion 61 Conclusions 63 Abstract 66 Zusammenfassung 67 Literature 68 Acknowledgments 81 Anlage 1: Erklärungen zur Eröffnung des Promotionsverfahrens 83 Anlage 2: Gesetzliche Vorgaben 84 The human skin surface contains considerable amounts of different lipids, both synthesized in deeper skin layers and migrating upwards (stratum corneum lipids), or generated in sebaceous glands and secreted on the skin surface (sebaceous lipids). Jointly the entirety of all skin surface lipids (SSLs) can be referred to as the skin lipidome. The composition of the skin lipidome is known to vary considerably. Lipids are product of several complex synthesis pathways, interconnected with the body’s metabolism. As such, lipid amounts may vary in response to what is happening inside of us. Lipid variations can be most pronounced when occurring in skin disorders, either as etiological cause or as effect, causing altered skin barrier properties. But certainly there is a range of variation in SSL amount which could be described as physiological. Attaining better knowledge of the physiological skin surface lipid variability is the purpose of this work for two main reasons. The first fundamental reason is to better understand skin biology. As major epidermis constituent, SSL composition and variability defines certain aspects of skin microanatomy, physiology and determines crucial skin properties. The second motivation is to acquire the ability to recognize what characterizes a sick skin lipidome. To this end, one must know how much a healthy skin lipidome can vary. To assess skin lipidome composition and variability, we developed and validated a quantitative high-throughput shotgun mass spectrometry-based platform for lipid analysis of tape-stripped stratum corneum (SC) skin samples. It features coverage of 16 lipid classes; total quantification to the level of individual lipid molecules; high reproducibility and high-throughput capabilities. With this method, we conducted the hitherto largest lipidomic survey of 268 human SC samples, where we investigated the relationship between sampling depth and lipid composition, lipidome variability in samples from 14 different sampling sites on the human body and finally, we assessed the impact of age and sex on lipidome variability in 104 healthy subjects.:The physiological lipidome of human epidermis Contents Abbreviations III Introduction 1 Architecture of the human shell 4 Measuring skin lipid composition 6 Skin sampling 6 Lipid extraction 9 Lipid identification 10 Lipid quantification 14 The design of this study 16 Material and methods 18 Method development and validation 18 Sampling development 18 Establishment of sample extraction and robotic handling 19 Establishment of mass spectrometric lipid identification 20 Establishment of lipid quantification 21 Skin lipidomic study 22 Sampling preparation 22 Standard sampling via tape stripping 23 Sampling via sequential tape-stripping 25 Lipid extraction 25 MS data acquisition 26 Lipid identification and data processing 27 Results 29 Method development and validation 29 Skin sampling via tape-stripping 29 Lipid extraction 31 Lipid identification 31 Lipid quantification 36 Skin lipidomic study results 38 Vertical skin surface lipid profile 38 Anatomical skin surface lipid variability 43 Inter-individual skin surface lipid variability 46 Discussion 50 Method development and validation 50 Skin sampling via tape-stripping 50 Lipid extraction 52 Lipid identification 53 Lipid quantification 55 Physiological lipid composition and variability 56 Lipidome variability vs sampling depth 56 Intra-individual lipidome variability 58 Inter-individual lipidome variability 59 General discussion 61 Conclusions 63 Abstract 66 Zusammenfassung 67 Literature 68 Acknowledgments 81 Anlage 1: Erklärungen zur Eröffnung des Promotionsverfahrens 83 Anlage 2: Gesetzliche Vorgaben 84

In this study, the dynamics and fracture of sandwich plates containing a pre-existing skin-to-core interfacial damage and subinterfacial core damage induced by an incident impact is examined. The dynamic response of sandwich plates with debonding that is allowed to be growing with a time, is simulated by using the finite element method within the ABAQUS code. The forced vibration analysis of impact-damaged sandwich plates is carried out accounting for contact and friction conditions within the debonded region in the simulations with ABAQUS. The damage mechanics approach implemented into ABAQUS via cohesive elements is used for modelling the debonding propagation under impulsive and harmonic loading. The influence of the skin-to-core debonding growth on the global nonlinear dynamics and strength of the sandwich plates is studied in detail.

A finite element (FE) model has been developed for analysis of the dynamic response of sandwich plates with partially damaged facesheet-to-core interface. The effect of intermittent dynamic contact between the fragments detached at the damaged interface is taken into account in the vibrating sandwich plate. The general mathematical statement of such non-linear elastodynamic problem for a cracked body is first formulated. Numerical results for the transient and steadystate dynamic responses of a foam-cored sandwich plate damaged by debonding are obtained by using the ABAQUS code. The influence of the strongly nonlinear local contact behavior on dynamics of the sandwich plate is examined.

A finite element (FE) model has been developed for analyzing the dynamic response of sandwich plates with a postimpact damage inducing core crushing, face sheet damage and core-to-face sheet debonding. Calculation of natural frequencies as well as simulation of strongly nonlinear transient dynamic response of impact-damaged sandwich plates is carried out with the ABAQUS code. The influence of parameters of impact-induced damage on dynamic behavior of sandwich plates with foam and nonmetallic honeycomb cores is discussed.

Dynamic responses of sandwich composite plates containing impactinduced damage are studied. A finite element formulation of the problem is developed by using the high-order sandwich plate theory. The finite element code ABAQUS is used to create a finite element model of the sandwich plate accounting for geometrical imperfections, stiffness changes and intermediate contact of detached plate parts caused by impact damage and to fulfil the free and forced vibration analyses.

The effect of polyvinyl chloride (PVC) foam filler on elastic properties of a regular hexagonal aluminum honeycomb core is studied. The unit cell strain energy homogenization approach based on the finite element method (FEM) within ABAQUS code is applied for prediction of effective material constants of the foam-filled honeycomb core. The developed FE model is then used to observe a three-dimensional stress state over the hexagonal unit cell and, thereby, to assess the influence of the foam-filling on the distribution of the local interfacial stresses.

Free vibrations of impact-damaged sandwich plates with honeycomb and foam cores are studied. It is assumed that damages caused by impact events are to exist before the vibration start and to be constant during oscillations. The influence of the impact damage modes involving the core crushing (planar damage), face sheets fracture (indentation) and the core to face sheets interface degradation (debonding) on the natural frequencies and associated mode shapes of the sandwich plates was investigated using commercially available finite element code ABAQUS.

The dynamic behavior of partially damaged at the skin/core interface sandwich plates with flexible honeycomb and polyvinyl chloride (PVC) foam cores are studied. The commercial finite element code ABAQUS is used to calculate natural frequencies and mode shapes of the sandwich plates with the debond zone. The effects of debonding size, debonding location and number of debonding on the modal parameters of damaged sandwich plates with various boundary conditions are investigated. The results of dynamic analysis illustrated that can be useful for analyzing practical problems related to the non-destructive damage detection of delaminated sandwich plates.

Free vibrations of impact-damaged sandwich plates with honeycomb and foam cores are studied. It is assumed that damages caused by impact events are to exist before the vibration start and to be constant during oscillations. The influence of the impact damage modes involving the core crushing (planar damage), face sheets fracture (indentation) and the core to face sheets interface degradation (debonding) on the natural frequencies and associated mode shapes of the sandwich plates is investigated using commercially available finite element code ABAQUSᵀᴹ.

Interlaminar fracture specimens like Double Cantilever Beam (DCB), End Notched Flexural (ENF), Single Leg Bending (SLB) etc. are widely used for studying the interlaminar toughness of composite laminates. The aim of this paper is to analysis delamination specimens within the framework of a meso-level damage modeling of composite laminates. In this case interlaminar interface is assumed as a damageable homogeneous layer between adjacent layers of the specimen bulk material. The degradation of the interlaminar connection can be taken into account by means either of an appropriate damage initiation criterion and damage evolution law or using fracture mechanics approach. Onset and growth of the delamination pre-existing crack in the fracture specimens are simulated by using both modeling possibility within commercial finite element code ABAQUSᵀᴹ. Comparisons between numerical predictions of used different finite element models as well as available experimental data have been performed.

The dynamic behavior of partially debonded at the skin/core interface sandwich plates with flexible cores is studied. The commercial finite element code ABAQUS is used to calculate natural frequencies and mode shapes of the debonded sandwich plates. The effects of debonding size, debonding location and number of debonding on the modal parameters of damaged sandwich plates with various boundary conditions are investigated. The results of dynamic analysis illustrated that can be useful for analyzing practical problems related to the non-destructive damage detection of debonded sandwich plates.

International audience

International audience