Cette étude s’attache à caractériser les mécanismes d’endommagement qui mènent à la rupture d'un alliage AlSi7Cu3Mg élaboré par un procédé à modèle perdu sous sollicitations cycliques isothermes à 250°C en condition de plasticité généralisée. Sa caractérisation par micro-tomographie aux rayons X (µCT) a montré la complexité et l'aspect 3D marqué de la microstructure: présence de pores de morphologies complexes de grandes tailles (>1mm) et d'un réseau inter-connecté de particules. Un montage expérimental a été développé pour réaliser des essais de fatigue à haute température suivis in situ par µCT synchrotron. Ces essais ont mis en évidence les interactions entre les fissures et les éléments microstructuraux. Les fissures s'amorcent au cœur des éprouvettes à proximité des cavités de retrait au niveau de particules dures. La propagation des fissures apparaît corrélée à la rupture progressive des particules présentes en pointe de fissure. Ces observations ont été complétées par des essais de fissuration réalisés sur des éprouvettes macroscopiques. Un matériau sans pore (similaire au premier) à été produit pour dissocier le rôle des pores et celui des particules dans la fissuration du matériau. L’influence des pores se révèle du premier ordre pour l’amorçage. Des maillages éléments finis réalistes ont été générés pour réaliser des simulations élasto-viscoplastiques qui ont permis de proposer un critère d’amorçage. Les zones critiques vis-à-vis de l’amorçage de fissures sont celles où l’énergie de déformation inélastique est maximale. Les chemins de fissuration correspondent aux zones localisant les déformations inélastiques et présentant de fortes triaxialités des contraintes. L’ensemble de ces analyses a donc permis de proposer un scénario complet d’endommagement. Enfin, les essais sur éprouvettes macroscopiques ont permis de proposer un modèle pour décrire la vitesse de propagation des fissures et ceci pour les deux matériaux. Ce modèle, facilement utilisable en bureau d’étude, a été validé pour différents niveaux de chargements. / This study aims to characterize the fatigue damage mechanisms that lead to the rupture of a cast aluminum alloy AlSi7Cu3Mg produced by lost foam casting at 250°C under large scale yielding. Its characterization by X-ray micro-tomography (µCT) showed the complexity and the strong 3D aspect of its microstructure: large pores with complex shapes (>1mm) and a network of interconnected hard particles are present. An experimental setup was developed to perform high-temperature fatigue tests monitored in situ by synchrotron µCT. These tests revealed the interactions between cracks and microstructural elements. Cracks initiated, in the bulk, on hard particles located in the vicinity of shrinkage cavities. Cracks propagation appears to be correlated to the progressive rupture of particles present in front of the crack tip. These observations were completed by crack growth tests carried out on macroscopic specimens. A pore-free material (similar to the first) was produced to dissociate the role of pores and particles on the low cycle fatigue behavior of the material. Pores appear to be more critical regarding cracks initiation. Realistic finite element meshes have been generated to perform elasto-viscoplastic simulations which have allowed to propose a criterion for cracks initiation. Critical areas regarding cracks initiation are correlated to areas where the inelastic strain energies are maximum. The crack paths correspond to areas where inelastic strains are located and where the levels of stress triaxiality are high. All these informations allowed to propose a damage scenario. Finally, the tests on macroscopic specimens allowed to propose a crack growth speed model for both materials. This model, easily usable by engineers, have been validated for different loadings.

I have worked on many projects, but there are several things that they all had in common. First, nearly all projects involved searching for the structural parameters that governed the macroscopic properties of the polymers and composite materials. A second common denominator is that even though my work was performed in an “academic context”, the goals were targeted toward industrial needs. Lastly, the methods and procedures were similar; they were all based on experimental results obtained for various scales of measurement (see Fig. 1). Hence, multi-scale modeling was very useful and beneficial for these projects. The models developed (mainly numerical and sometimes analytical) were initially derived from experimental evidence and then validated and improved with further experimentation. The refined models provided an efficient means of: (i) optimizing the composites according to specific needs, (ii) better understanding the hierarchical relations between the different scales, (iii) controlling the micro or meso structure and thereby the macroscopic properties. This study of the relations between structure and properties was performed on a wide variety of physical properties and materials. However, the electric and dielectric properties of composites constituted the major- ity of it and will be presented in this report. The remaining property investigations provided supplemental but valuable information. This work often requires altering various conventional experimental techniques or using well-known techniques for new purposes. I also developed, when needed, several unconventional but necessary measurement techniques. This report contains two major parts which are separated according to the nature of the fillers: Part I : Conducting fillers. In the first part, the main interest both for application and fundamental point of view, is related to the changes in properties in the vicinity of the sharp percolation transition. After a brief introduction to the percolation theory, this part will be subdivided in three chapters: Chapter 1. presents a numerical method that correlates the mesostructure to the macroscopic electrical properties both in two and three dimensions. Chapter 2. will show that an external variable (the mechanical stress) may largely alter the microstruc- ture of the percolating network within composites as revealed the macroscopic conductivity. The understanding of the mesoscale changes will be based on the chemical structure of the polymer matrix. Chapter 3. is devoted to the description of a unique case in term of percolation behavior, which made possible the control of the phase arrangement within the composite and thereby the control of the macroscopic resistivity. p. 2 Multiscale relationships in polymer–based heterogeneous systems. . . Part II : Insulating fillers. In the second part, the main interest is to obtain good electrical insulators, i.e. that can withstand large electric fields. This part thus starts with a brief introduction to the common failure mechanisms, associated with the dielectric breakdown and is also divided in three chapters: Chapter 4. is devoted to the description of a numerical simulation of the relationships between mesostructure and dielectric breakdown. Chapter 5. reveals the influence of the processing conditions of a composite utilized in the industry on the microstructure and the quantitative consequences on breakdown properties. Chapter 6. presents the aging of these composites under “real word” conditions which will further be compared to accelerated aging performed in controlled conditions, in the laboratory. A comparison of the two aging situations will furnish a quantitative understanding of the relative influence of the chemical and physical contributions to the aging process. This report will then be concluded with a description of the current and future projects.

Nonlinear finite element models of functionally graded beams with power-law variation of material, accounting for the von-Karman geometric nonlinearity and temperature dependent material properties as well as microstructure dependent length scale have been developed using the Euler-Bernoulli as well as the first-order and third- order beam theories. To capture the size effect, a modified couple stress theory with one length scale parameter is used. Such theories play crucial role in predicting accurate deflections of micro- and nano-beam structures. A general third order beam theory for microstructure dependent beam has been developed for functionally graded beams for the first time using a modified couple stress theory with the von Karman nonlinear strain. Finite element models of the three beam theories have been developed. The thermo-mechanical coupling as well as the bending-stretching coupling play significant role in the deflection response. Numerical results are presented to show the effect of nonlinearity, power-law index, microstructural length scale, and boundary conditions on the bending response of beams under thermo-mechanical loads. In general, the effect of microstructural parameter is to stiffen the beam, while shear deformation has the effect of modeling more realistically as a flexible beam.

L’objectif principal de cette thèse est de modéliser en flambement des poutres pressurisées en tissu souple homogène orthotrope (THO) composite. La première partie détaille les études expérimentales qui ont été menées sur des poutres gonflables à certain niveaux de pression afin de caractériser les propriétés mécaniques du matériau et le comportement en flambement de la structure. Dans une deuxième partie, une approche analytique a été envisagée afin d’étudier le flambement ainsi que le comportement d’une poutre gonflable orthotrope. Un modèle 3D gonflables poutre orthotrope basé sur la cinématique de Timoshenko a été présenté brièvement. La charge critique a été étudiée pour différents cas de charge avec différentes conditions aux limites. Les résultats ont été confrontés aux résultats théoriques disponibles. Pour vérifier la limite de validité des résultats, la charge d’apparition des plis a également fait l’objet d’une étude pour chacun des cas. La dernière partie est consacrée à une étude linéaire et à une analyse non-linéaire du flambement de la poutre gonflable en THO composite. Le modèle éléments finis (MEF) établi ici implique un élément poutre de Timoshenko à trois-nœuds avec une continuité de type C0. Un test de convergence du maillage sur la force critique de la poutre a été réalisé par la résolution du problème aux valeurs propres. En outre, un MEF non-linéaire a été développé en utilisant la procédure itérative de quasi-Newton avec incréments de chargement adaptatif permettant le tracé pas à pas de la réponse charge-déflexion de la poutre. Les résultats ont été validés à partir d’un certain niveau de pression par des résultats expérimentaux et numériques / The main goals of this thesis are to modeling and to perform the buckling study of inflatable beams made from homogeneous orthotropic woven fabric (HOWF) composite. Three main scenarios were investigated in this thesis. The first is the experimental studies which were performed on HOWF inflatable beam in various inflation pressures for characterizing the orthotropic mechanical properties and buckling behaviors of the beam. In the second scenario, an analytical approach was considered to study the buckling and the behavior of an inflatable orthotropic beam. A 3D inflatable orthotropic beam model based on the Timoshenko's kinematics was briefly introduced: the nonlinearities (finite rotation, follower forces) were included in this model. The results were compared with theoretical results available in the literature. To check the limit of validity of the results, the wrinkling load was also presented in every case. The last scenario is devoted to the linear eigen and non-linear buckling analysis of inflatable beam made of HOWF. The finite element (FE) model established here involves a three-noded Timoshenko beam element with C0-type continuity for the transverse displacement and quadratic shape functions for the bending rotation and the axial displacement. In the linear buckling analysis, a mesh convergence test on the beam critical load was carried out by solving the linearized eigenvalue problem. In addition, a nonlinear FE model was developed by using the quasi-Newton iteration with adaptive load stepping for tracing load-deflection response of the beam. The results were validated from a certain pressure level by experimental and thin-shell FE results

En France, un tiers des personnes tuées sur la route le sont lors d’un accident sur un obstaclefixe. Dans 90% des cas, ces accidents surviennent après une perte de contrôle du véhicule.Les dispositifs de retenue de véhicule ont pour but de maintenir les véhicules en perdition surla chaussée en limitant la sévérité de l’impact.Ces dispositifs doivent subir des essais de chocs normatifs afin de pouvoir être installés sur lebord des routes européennes et d’évaluer leurs performances en termes de sévérité et dedéflexion.Les tolérances existantes sur les paramètres d’essai (véhicule, masse du véhicule, vitesse,angle et point d’impact …) et les incertitudes sur les caractéristiques mécaniques desmatériaux constituant le dispositif ont un effet sur les performances de ce dispositifs etdoivent être prises en compte lors des calculsLes dispositifs mixtes (acier-bois) présentent une difficulté supplémentaire en raison del’hétérogénéité du matériau et de sa sensibilité aux variables d’environnement telles que latempérature et l’humidité.Afin de prendre en compte cette variabilité et d’évaluer son impact sur les performances d’undispositif, des essais dynamiques sur des échantillons de structure ont été réalisés et modélisésnumériquement.Enfin, un modèle complet d’un dispositif de retenue de véhicule a été effectué et corrélé surun essai de choc réel à l’aide d’une méthode prenant en compte la variation de paramètresphysiques liés à l’apparition des modes de ruine de la structure. Une fois corrélé, le modèle aété utilisé afin d’évaluer l’incidence de la modification des caractéristiques mécaniques dubois liée aux variations des conditions environnementales. / In France, one third of the people dying on the roads are killed after impacting against ahazard. In 90% of the reported cases, these accidents result from loss of control. VehicleRestraint Systems (VRS) are specially designed to restrain an errant vehicle and to limitimpact severity.Before being installed on the roadsides, these devices have to be crash-tested according tostandards in order to evaluate their safety and deflexion performances.Tolerances exist on impact parameters (vehicle, vehicle mass, impact speed, impact angle,impact point …) and material’s mechanical characteristic uncertainties have an effect towardsdevice performances and have to be taken into account during numerical simulations.Steel-wood structures present an additional numerical challenge due to wood heterogeneityand its sensibility to environment variables such as temperature and moisture content.In order to assess the effect of this variability toward safety performances, three point bendingdynamic experiments on structural samples are performed and modelled.Finally, a complete model of a vehicle restraint system is built and validated according to realcrash test results thanks to a parametric method. This method takes into account the variabilityof the parameters associated to the failure modes of the structure. Once validated the model isused to assess the effect of wood mechanical properties modifications due to environmentvariable variations.

Accidents involving passenger trains happen regularly in India. The reasons for such accidents could be many; such as weather and flooding, faulty tracks, bridge collapse, collisions caused by signaling errors, mechanical failures, driver error, sabotage etc. The annual accident-related deaths as a percentage of the total number of passengers carried by Indian Railway may seem to be negligible, but the aim should be to achieve zero fatality as every single person killed is an irreplaceable loss to his/her family. It needs to be mentioned that in addition to fatalities for which exact numbers are not available, serious injuries and permanent disabilities caused by train accidents in India at present stand completely unaccounted for. In the absence of a large scale renovation and crash avoidance measures coupled with the propensity to increase the number of trains every year, enhancing passive safety is crucial i.e. crashworthiness and occupant safety of passenger coaches of Indian trains. In the current work, crashworthiness and occupant safety of the existing typical three-tier cabin passenger coach of Indian Railway in an event of collision accident are assessed with the aid of a finite element analysis. In the light of the published work on research in railroad equipment crashworthiness, the current work is intended to envisage the methodology to assess the Indian Railway passenger coach from the point of view of the crashworthiness and occupant safety using CAE (Computer aided engineering) based approach. It is involved with an extensive study of the structural crush behavior of an individual passenger coach car and its effect on the interaction between occupants and the coach interior. Here the structural crush behavior of a typical three-tier cabin passenger coach is evaluated for the head-on impact against a fixed and rigid barrier. The occupant response for the same scenario is also studied which can be viewed as a component of the actual occupant response due to the structural crush behavior of the passenger coach. This can give useful estimates of injury severity and fatalities that may occur in actual accidents. An FE model of the passenger coach structure was built and validated using International Railway Union (UIC) specified code OR 567-design requirements in terms of static loads constituting structural proof cases. These proof cases specify the static load values the coach body structure should withstand without any permanent deformation or failure when applied at the specified locations on the structural ends across the longitudinal axis. In addition, a favorable correlation between the simulation and actual experiment for drop impact behavior of the open section specimens, namely C-section and I-section, was obtained to validate the simulation methodology. LS-DYNA a nonlinear dynamic explicit FE solver was used to carry out all the dynamic impact simulations involved in the current work. The material modeling takes into account the strain rate effect which is essential for the material impact behavior study. The contact modeling was done using penalty contact method. The degrading effect of the buffer on the structural crush patterns which induced the undesirable global bending and jackknifing of the whole coach structure was demonstrated with the help of dynamic impact simulations of the coach structure. The quantification of occupant injury was done by occupant safety simulations using the Hybrid III 50th percentile male dummy FE model. The dummy having been designed for simulating automobile accident scenarios, its contacts had to be adapted to suit the excessive mobility conditions in the coach interior. The dummy was revalidated successfully for the head drop test, pendulum chest impact test, neck flexion and extension test and knee impact test. Impact simulations for three different speeds were performed by positioning the dummy close to the impact point. Injury criteria such as Head Injury Criterion, Chest Deceleration, Knee force level and Neck extension-flexion moments were used to estimate the injury severity level and fatality rate.

Thesis deals with determination of layerwise mechanical properties of composite ceramics by indirect method, namely Youngs modulus. Based on literature review, it was found that a method to determine elastic properties of one or more components of multi layered composites based on experimental modal analysis and finite element modal analysis, or analytical approach exists. Method based on FE modal analysis was applied to ceramic laminate, where it was attempt to determine youngs modulus of one component. Beyond that, it was attempt to determine Youngs moduli of both components using first two bending resonant frequencies. Results were unsatisfying. Sensitivity analysis showed that layers with unknown Youngs modulus were overly sensitive to small changes in input parameters due to their small relative thickness with respect to thickness of laminate and due to location in laminate. Based on this conclusion, recommendations were made with respect to suitable geometry of test specimens.

This paper presents a method of parameter identification for a finite-element model of the human middle ear. The parameter values are estimated using a characterization of the difference in natural frequencies and mode shapes of the tympanic membrane between the model and the specimens. Experimental results were obtained from temporal bone specimens under sound excitation (300–3,000 Hz). The first 3 modes of the tympanic membrane could be observed with a laser scanning vibrometer and were used to estimate the stiffness parameters for the orthotropic finite-element model of the eardrum. A further point of discussion is the parameter sensitivity and its implication for the identification process. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Pour mieux comprendre et traiter les troubles musculosquelettiques présents à l’épaule, une meilleure connaissance de la contribution et de la fonction de chaque muscle de l’articulation glénohumérale est nécessaire. L’analyse des forces musculaires et articulaires est une étape importante pour comprendre les mécanismes de blessures et les pathologies. Ces forces musculaires peuvent être estimées de façon non invasive grâce à des modèles musculosquelettiques. Le défi est de prédire de façon physiologique les trajectoires musculaires et les bras de levier afin de s’assurer d’avoir une cohérence des forces musculaires dans les modèles musculosquelettiques. L’objectif de cette thèse était d’améliorer la géométrie musculaire des modèles musculosquelettiques de l’épaule en passant par plusieurs méthodes différentes d’implémentation des trajectoires musculaires. À cet égard, nos objectifs spécifiques étaient de : (1) améliorer la géométrie musculaire des modèles multicorps rigides grâce à l’implémentation de contraintes transverses; (2) évaluer la fiabilité d’un modèle éléments finis pour l’estimation des bras de levier et (3) tester la sensibilité de la prédiction des bras de levier aux incertitudes sur les zones d’insertions musculaires; (4) établir une base de données de bras de levier 3D pour des mouvements de grande amplitude; (5) quantifier de façon expérimentale les changements architecturaux des muscles entre l’état au repos et différents niveaux de contraction isométrique. (1) Deux modèles multicorps rigides de la coiffe des rotateurs ont été développés : un modèle classique intégrant une représentation des lignes d’action en 1D et un modèle possédant des contraintes transverses entre les lignes d’action permettant une représentation 2D. La représentation 2D avec des contraintes transverses permet une représentation plus physiologique des trajectoires musculaires et des bras de levier que les modèles classiques 1D. Toutefois, lors de mouvement allant au-delà de 90° d’élévation du bras, lorsque les points d’origine et d’insertion se rapprochent, les bras de levier et les longueurs musculaires sont mal estimés, car le modèle ne prend pas en compte les déformations du volume musculaire. (2) Un modèle éléments finis a été développé à partir de données d’imagerie médicale. Ce modèle permet une estimation des bras de levier fidèle aux données d’IRM. Contrairement aux modèles multicorps rigides, notre modèle élément finis rend compte du fait qu’un même muscle peut avoir plusieurs actions selon la position de sa ligne d’action par rapport au centre de rotation de l’articulation. (3) Le modèle a également servi à faire une étude de sensibilité des bras de levier : les zones d’insertion des différents muscles de la coiffe des rotateurs et du deltoïde ont été déplacées et les bras de levier associés calculés. Les résultats montrent qu’une variation de 10 mm des points d’insertion sur la tête humérale peut amener un muscle à changer de fonction (par exemple adduction plutôt que d’abduction). (4) Une collecte de données expérimentales effectuées sur quatre épaules a permis de collecter les bras de levier du deltoïde et des muscles de la coiffe des rotateurs pour des mouvements de grande amplitude. Ces résultats permettent de mieux comprendre le rôle des muscles de l’articulation glénohumérale lors de la réalisation de différents mouvements. Le deltoïde antérieur a une grande action en flexion et en adduction; le deltoïde moyen est un fort abducteur; le deltoïde postérieur agit en extension. Contrairement au deltoïde, l’infra-épineux et le petit rond ont principalement une fonction de rotateur externe. (5) Une collecte de données impliquant 14 sujets a été réalisée dans le but de quantifier les changements de géométrie musculaire et d’angle de pennation associés à la contraction pour les muscles du biceps, triceps et deltoïde. Les angles de pennation ont été obtenus grâce à un système d’échographie et les changements de géométrie externe des muscles ont été mesurés grâce à un capteur de structure. Les résultats montrent que les changements architecturaux pour les muscles étudiés se produisent principalement entre 0 et 25% de contraction maximale volontaire (aucune différence significative observée entre 25 et 50%). Le muscle le plus affecté par les changements architecturaux est le biceps. Cette thèse a évalué différentes approches de modélisation de la géométrie musculaire : l’approche la plus bio-fidèle étant finalement la modélisation par éléments finis, car elle permet de prendre en compte les interactions entre les structures et les déformations musculaires. De plus, nous avons montré l’importance d’estimer avec rigueur les paramètres d’entrée (zones d’insertions musculaires) des modèles et de bien évaluer la bio-fidèlité des modèles développés avant de les utiliser dans des contextes cliniques. Dans ce but, de nouvelles données ont été acquises en termes de déformations musculaires et d’angle de pennation pour permettre l’évaluation de modèle intégrant de l’activation musculaire. / Understanding and treating musculoskeletal disorders of the shoulder requires additional knowledge of the contribution and function of each muscle of the glenohumeral joint. The analysis of muscle and joint forces is an important step in understanding injury mechanisms and pathologies. These muscle forces can be estimated non-invasively using musculoskeletal models. The challenge is to physiologically predict muscle trajectories and moment arms to ensure consistency of muscle forces in musculoskeletal models. The aim of this thesis was to improve muscle geometry in musculoskeletal models of the shoulder by testing several different techniques for implementing muscle trajectories. Our specific objectives were to: (1) improve muscle geometry of rigid multibody models by using transverse constraints; (2) assess the reliability of a finite element model for estimating moment arms and (3) evaluate the sensitivity of moment arm predictions to uncertainties in muscle insertion areas; (4) create a database of 3D moment arms for movements with high ranges of motion; (5) experimentally quantify muscles’ architectural changes between resting state and different levels of isometric contractions. (1) Two rigid multibody models of the rotator cuff were developed: a classic model representing muscles with lines of action in 1D and a 2D model with transverse constraints between lines of action of a single muscle. The 2D model (with transverse constraints) gives a more physiological representation of muscle trajectories and moment arms than the classical 1D model. However, for arm movements beyond 90° of elevation, when the origin and insertion points get closer, moment arms and muscle lengths are misestimated due to the mode’s inability to account for muscle volume deformations. (2) A finite element model of the glenohumeral joint was developed based on medical imaging. Moment arms were computed and compared to the literature and MRI data. Our finite element model produces moment arms consistent with the literature and MRI data. Unlike rigid multibody models, our finite element model accounts for the fact that one muscle can have several actions depending on the position of its line of action relative to the centre of rotation of the joint. (3) The model was used to study moment arm sensitivity: insertion areas of rotator cuff muscles and the deltoid were moved, and associated moment arms have been computed. Results showed that a 10 mm variation in insertion points on the humeral head could cause a muscle to change function (for example performing adduction rather than abduction). (4) The 3D moment arms were assessed on four post-mortem human surrogates during movements with high ranges of motion. Results of the study gave us a better understanding of muscle functions during different movements. The main findings of the study were that the anterior deltoid was the largest flexor and had an adduction component, the median deltoid was a strong abductor, and the posterior deltoid acted in extension. Unlike the deltoid, the infraspinatus and teres minor were the largest external rotators of the shoulder. (5) Experimental measurements were performed on 14 subjects in order to quantify changes in muscle geometry and pennation angles associated with different levels of contraction for the biceps, triceps and deltoid. Pennation angles were measured on subjects using a portable ultrasound system. External muscle deformations were measured with an iPad equipped with a structure sensor. Changes in muscle architecture for the biceps, triceps and deltoid during isometric contractions occurred mostly between 0 and 25% of maximal voluntary contraction (no significant difference was observed between 25 and 50%). Changes were higher for the biceps than other muscles. This thesis evaluated different approaches to model muscle geometry: the approach leading to the most physiological result was the finite element model due to modeling of the interactions between structure and muscle deformations. Additionally, we demonstrated the importance of rigorously estimating input parameters (muscle insertion areas) and of properly evaluating the bio-fidelity of the models developed before using them in clinical contexts. New data was acquired regarding muscle deformations and pennation angles to evaluate models integrating muscle activation.

To prevent the renewed rupture of ligaments and tendons prior to the completed healing process, which frequently occurs in treated ruptured tendons, a temporary support structure is envisaged. The limitations of current grafts have motivated the investigation of tissue-engineered ligament replacements based on the braiding technology. This technology offers a wide range of flexibility and adjustable geometrical and structural parameters. The presented work demonstrates the possible range for tailoring the mechanical properties of polyester braids and a variation of the braiding process parameters. A finite element simulation model of the braiding process was developed, which allows the optimization of production parameters without the performance of further experimental trials. In a second modelling and simulation step, mechanical properties of the braided structures were virtually determined and compared with actual tests. The digital element approach was used for the yarns in the numerical model. The results show very good agreement for the process model in terms of braiding angles and good agreement for the structural model in terms of force-strain behaviour. With a few adaptions, the models can, thus, be applied to actual ligament replacements made of resorbable polymers.