Silicon (Si)-based materials are sought in different engineering applications including Civil, Mechanical, Chemical, Materials, Energy and Minerals engineering. Silicon and Silicon dioxide are processed extensively in the industries in granular form, for example to develop durable concrete, shock and fracture resistant materials, biological, optical, mechanical and electronic devices which offer significant advantages over existing technologies. Here we focus on the constitutive behaviour of Si-based granular materials under mechanical shearing. In the recent times, it is widely recognised in the literature that the microscopic origin of shear strength in granular assemblies are associated with their ability to establish anisotropic networks (fabrics) comprising strong-force transmitting inter-particle contacts under shear loading. Strong contacts pertain to the relatively small number of contacts carrying greater than the average normal contact force. However, information on how such fabrics evolve in Si-based assemblies under mechanical loading, and their link to bulk shear strength of such assemblies are scarce in the literature. Using discrete element method (DEM), here we present results on how Si-based granular assemblies develop shear strength and their internal fabric structures under bi-axial quasi-static compression loading. Based on the analysis, a simple constitutive relation is presented for the bulk shear strength of the Si-based assemblies relating with their internal fabric anisotropy of the heavily loaded contacts. These findings could help to develop structure-processing property relations of Si-based materials in future, which originate at the microscale.

This review aims to consolidate scarce literature on the use of modern nanomechanical testing technique like instrumented nanoindentation in the field of archaeometry materials research. The review showcase on how can the nanoindentation tests provide valuable data about mechanical properties which, in turn, relate to the evolution of ancient biomaterials as well as human history and production methods. This is particularly useful when the testing is limited by confined volumes and small material samples (since the contact size is in the order of few microns). As an emerging novel application, some special considerations are warranted for characterization of archaeometry materials. In this review, potential research areas relating to how nanoindentation is expected to benefit and help improve existing practices in archaeometry are identified. It is expected that these insights will raise awareness for use of nanoindentation at various world heritage sites as well as various museums.

A novel micromechanical approach is proposed to calculate the effective thermal conductivities of fiber reinforced composite materials. The key advantage of the present formulation is its ability to yield closed form solutions for the effective thermal conductivity of composites in both longitudinal and transverse directions for three dimensional heat transfer problems. The obtained results are in good agreement with the experimental data reported in the literature. When compared with analytical and finite element solutions, the results are seen to be in better agreement with the hexagonal packed array compared to the square packed array which thus represents a more realistic model of the fiber distribution in the matrix medium.

In this study, a fully micromechanical model based on iso-field assumptions is developed for computing the effective coupled thermo-electro-elastic material properties of Macro Fiber Composites (MFCs) in the linear regime. The explicit formulations are derived using the thermo-electro-elastic constitutive equations under the iso-field assumptions and multiple loading conditions. The effects of piezoelectric fiber volume fraction and matrix properties on the effective material constants of MFCs are studied through some examples. In order to validate the accuracy of the present micromechanical formulations, comparisons have been made with other results available in the literature.

In this paper, a new algorithm is developed based on the homogenization method integrating with the newly developed Hybrid Treffe FEM (HT-FEM) and Hybrid Fundamental Solution based FEM (HFS-FEM). The algorithm can be used to evaluate effective elastic properties of heterogeneous composites. The representative volume element (RVE) of fiber reinforced composites with periodic boundary conditions is introduced and used in our numerical analysis. The proposed algorithm is assessed through two numerical examples with different mesh density and element geometry and used to investigate the effect of fiber volume fraction, fiber shape and configuration on the effective properties of composites. It is found that the proposed algorithm is insensitive to element geometry and mesh density compared with the traditional FEM (e.g. ABAQUS). The numerical results indicate that the HT-FEM and HFS-FEM are promising in micromechanical modeling of heterogeneous materials containing inclusions of various shapes and distributions. They are potential to be used for future application in multiscale simulation.

Osteoporosis is a disease characterized by a loss of bone density and an altered bonearchitecture. These modifications lead to an increased risk factor for bone fracture,particularly of the femoral neck. This disease can be explained by a disorder in the boneremodeling process which is triggered by the apparition of micro-cracks within the bone.According to Frost’s theory [1], these micro-cracksappear for a specific local strain threshold. Thus, the knowledge of the microarchitectureand quality of trabecular bone is essential to determine this local strain threshold. Thispaper studied the mechanical trabecular bone behavior of 43 patients diagnosed asosteoporotic whose femoral heads were replaced by hip prosthesis. From each patient, acylinder-shaped of trabecular bone samples was cored. Each sample was scanned by X-raymicro-tomography before a compression test in order to reconstruct a reliableFinite-Element (FE) model of the bone architecture in Abaqus. The force-displacementcurves were recorded for all the samples and calibrated by the experimental responses. Theforce-displacement numerical curves were adjusted to the experimental ones, by modifyingthe tissue microscopic mechanical behavior. This process leads to the determination of thelocal strain threshold responsible for triggering the bone remodeling process.

Based the previously published model on the two-dimensional micromechanical fiber interaction framework of two-phase composites, effective transverse elastic properties of composites containing two types of randomly located yet unidirectionally aligned circular fibers are studied in this paper. Approximate local solutions for the interaction problem of two randomly located circular fibers of different elastic properties are presented. A fiber-reinforced composite material containing two extreme types of inclusions, voids and rigid fibers, is also investigated. Comparison with Hashin's variational bounds and Mori-Tanaka method, the current approach provides reasonably accurate predictions for three-phase composites. Finally, numerical simulation examples are implemented to demonstrate the capability of the proposed model.

Une approche multiéchelle de la fatiguemultiaxiale en endurance illimitée est proposée. Elle vise àrendre compte des mécanismes couplés de plasticité et d'endommagement quisurviennent le long des Bandes de Glissement Persistantes (BGP).L'endommagement, qui est couplé avec la plasticité, est modélisécomme la conséquence de la croissance de microcavités le long desBGP. Le critère de fatigue macroscopique proposé correspond à unecondition de nucléation d'une fissure à l'interface BGP/matrice,et est obtenu pour le schéma d'homogénéisation de Kröner. Onmontre le rôle de la contrainte moyenne et de la pressionhydrostatique en fatigue à grand nombre de cycles. Cettedépendance est ici liée à la prise en compte des micromécanismesd'endommagement. Enfin, on présente quelques illustrations dans lecas particulier des trajets de chargement affines. Descomparaisons du critère obtenu avec desrésultats expérimentaux montrent la pertinence de l'approche.

Les aciers TRIP présentent une ductilité élevée et une forte résistance. Cette propriété remarquable trouve son origine dans la transformation martensitique de l'austénite. Ce comportement est modélisé avec une approche par transition d'échelle en utilisant le cadre de la thermomicromécanique pour déterminer les forces motrices ainsi que les lois de germination et de croissance qui contrôlent l'évolution de la microstructure. La présence de frontières mobiles et la discontinuité du champ de déformation au passage de ces interfaces sont prises en compte dans l'écriture des équations de champs. On montre que le champ de contrainte interne associé à la transformation se compose d'une contribution à longue distance responsable de la sélection des variantes et d'une contribution locale liée à la morphologie des microdomaines et au mode de croissance. On utilise une approche cristallographique à variables internes pour déterminer ces contributions. L'utilisation d'un modèle auto-cohérent classique permet ensuite de décrire le comportement global. Les résultats numériques obtenus sont comparés avec les données expérimentales pour un alliage FeNi et un acier TRIP 0,2C-1,5Si-1,5Mn élaboré par l'IRSID.

At present, mechanisms by which specific structural and mechanical properties of the three-dimensional extracellular matrix microenvironment influence cell behavior are not known. Lack of such knowledge precludes formulation of engineered scaffolds or tissue constructs that would deliver specific growth-inductive signals required for improved tissue restoration. This article describes a new mechanical loading–imaging technique that allows investigations of structural–mechanical properties of biomaterials as well as the structural–mechanical basis of cell–scaffold interactions at a microscopic level and in three dimensions. The technique is based upon the integration of a modified, miniature mechanical loading instrument with a confocal microscope. Confocal microscopy is conducted in a reflection and/or fluorescence mode for selective visualization of load-induced changes to the scaffold and any resident cells, while maintaining each specimen in a “live,” fully hydrated state. This innovative technique offers several advantages over current biomechanics methodologies, including simultaneous visualization of scaffold and/or cell microstructure in three dimensions during mechanical loading; quantification of macroscopic mechanical parameters including true stress and strain; and the ability to perform multiple analyses on the same specimen. This technique was used to determine the structural–mechanical properties of three very different biological materials: a reconstituted collagen matrix, a tissue-derived biomaterial, and a tissue construct representing cells and matrix.