An experimental method for determining the in-plane shear modulus of carbon fibres

International audienceThe performance of bituminous materials is often evaluated using rheological properties measured within the linear viscoelastic region. If there is a univocal temperature dependence of all the relaxation times, data obtained in different operating conditions can be translated onto a logarithmic scale where they partially overlap and merge into a single master curve. This is the well-known time–temperature superposition principle that has been successfully applied for decades. However, the empirical nature of the method has led to many different procedures being used for the graphical construction of the master curve. In addition, the continuously increasing calculating power has led to new approaches, such as the simultaneous modelling of the represented viscoelastic function. Losing track of the basic statements of the method is the hidden drawback of this wide range of available protocols with the risk of artefacts and incongruences being introduced in the construction of the master curves. This review summarizes these basic statements together with the empirical and phenomenological approaches developed over the years. The aim of this study is to help the reader in choosing the most appropriate method to build the master curves. Although the subject of the review is of general application, the field of bitumen is focused on

Static bending of micromorphic Timoshenko beams

International audienceAbstract This paper investigates statics and natural vibration of linear elastic cubic lattices, together with their continuum approximations. The lattice endowed with central and angular interactions, referred to as Gazis et al . ’s, is considered first: since the stiffness of each lattice phase must be positive, the equivalent macroscopic Poisson’s ratio must be lower than its central limit 1/4. A volumetric interaction based on a volume-dependent internal pressure is introduced as an additional non-central interaction for a complete calibration of the equivalent Poisson’s ratio up to its incompressibility limit 1/2. This volumetric interaction can also be classified as Fuchs-type, providing a potential energy that depends on the volume variation of each cell. The mixed differential-difference equations of the associated lattice derive from Hamilton’s principle applied to the discrete energies. The algebraic properties of the stiffness matrix of the discrete cell provide information on the positive definiteness of the potential energy, for each lattice with central and non-central interactions. The convergence of this finite lattice towards a linear elastic continuous right parallelepiped is shown in several static loading schemes. The discrete Lamé problem for the free vibration of this parallelepiped is solved for all the considered lattices. It is concluded that discrete and continuum elasticity can be connected by this cubic lattice within a complete range of elasticity parameters

Integrative assessment of biohydrogen and biomethane production from Brittany and Caribbean Sargassum (Ochrophyta, Fucales)

International audienc

Comparative study of three cellular materials under blast and sustained shock wave

International audienceThis study investigates the mechanical response of three cellular materials—polyisocyanurate (PIR), autoclaved aerated concrete (AAC), and Aluminum Lightweight Foam (ALF, Nufoam® 140)—under blast and shock loading conditions. The research aims to provide experimental data for optimizing building protection against explosion hazards. Laboratory-scale tests were conducted using a shock tube to generate blast and sustained shock waves. The materials’ responses were analyzed using high-speed imaging and digital image correlation. Results indicate that PIR exhibits significant deformation under sustained shocks but shows recovery under blast loading. AAC demonstrates erosion-based energy dissipation, with material loss concentrated at the extremities. ALF, serving as a reference, shows excellent mechanical energy dissipation. The study highlights the potential of these materials for applications requiring both thermal insulation and blast resistance, contributing to the development of predictive tools and larger-scale experiment designs

Decoupling surface stiffness from surface chemistry: Impact on bacterial adhesion and retention under shear conditions

International audienceUnderstanding how substrate mechanics influence bacterial adhesion and retention is essential for controlling biofilm formation on synthetic materials. Studies on soft polymers such as PDMS are often confounded by uncontrolled variations in surface chemistry and topography. In this work, a PS-PIB bilayer system was designed to decouple surface chemistry from mechanics, enabling independent control of stiffness while maintaining constant surface properties. Static adhesion assays with Pseudomonas aeruginosa PAO1 showed that initial attachment was insensitive to substrate modulus when surface chemistry and roughness were held constant. In contrast, retention under shear flow decreased with increasing stiffness and correlated more closely with the work of separation obtained from nanoindentation experiments. This parameter, which integrates both adhesive and dissipative contributions, is introduced as an empirical descriptor of interfacial mechanical resistance. Retention data were described by a power-law model consistent with stochastic frameworks of multivalent adhesion, reflecting population heterogeneity in the number and strength of adhesive contacts. Altogether, these findings suggest that viscoelastic dissipation is a key factor influencing P. aeruginosa PAO1 detachment under flow and highlight the need for future studies using bacterial mutants and diverse species to assess the generality of this correlation across different adhesion strategies

A solar-powered multi-functional portable charging device (SPMFPCD) with internet-of-things (IoT)-based real-time monitoring—An innovative scheme towards energy access and management

International audienceBattery energy storage system (BESS) Internet of thing (IoT) Real-time monitoring Disaster management technology Economic viability Emergency medical charging solutions Mul-ti-functional charging device Public spaces charging infrastructure Renewable energy integration (REI) Solar-powered portable charging In the absence of portable charging devices, sectors such as transportation, communication, and emergency services deal with various challenges towards electric power needs while compromising on (1) operational efficiency, (2) insufficient portable charging solutions, and (3) limited versatility. This highlights the critical need for reliable and multi-functional power solutions. To provide a portable charging solution across diverse sectors, this paper proposes an innovative development of a solar-powered multi-functional portable charging device (SPMFPCD) with internet-of-thing (IoT)-based monitoring capabilities. The proposed scheme introduces a comprehensive model integrating advanced technologies which include a highly efficient solar panel, charge controller, sensors, and IoT module. The proposed system facilitates versatile charging solutions for a wide range of power requirements with real-time monitoring and data analysis through the IoT platform. Moreover, the proposed work explores the applications of the SPMFPCD in (1) emergency medical scenarios, (2) outdoor adventures, (3) disaster management, and 4) public spaces. Performance evaluation was made by proposing case studies to validate the (1) economic viability, (2) power management, and (3) environmental impact of widespread deployment of SPMPFCD in public spaces. Furthermore, detailed analysis of battery energy storage system (BESS) and photovoltaic (PV) integration for load management, seasonal dynamics, and renewable energy integration (REI) contribute to a comprehensive understanding of the proposed solution

Modélisation du thermoformage de structures en composites tubulaires, et de ses conséquences sur ses propriétés en service

International audienceModélisation du thermoformage de structures en composites tubulaires, et de ses conséquences sur ses propriétés en servic

Green's functions for the static curvature and deflection of two-phase peridynamic elastic Euler-Bernoulli beams with exponential kernels

International audienc

Virtual forming based on model calibration from heterogeneous tests

International audienceAbstract. This study focuses on calibrating a mechanical model for a DP600 steel using both quasi-homogeneous and heterogeneous tests. Several sample geometries subject to a uniaxial load were selected and tested experimentally, and a finite element model updating method was used to identify the material parameters of an anisotropic plasticity model, leading to several material parameter sets. Then, the virtual forming of cylindrical cup is considered, using these different parameter sets. The strain and stress states of the mechanical tests used for the model calibration are compared with those of the forming process, to analyse their relevance. The main goal is to check the whole chain from the indicator-based design of heterogeneous tests up to a numerical case study of the forming of cylindrical cups

Des nombres de Cantor et de Dedekind aux nombres de Conway - Partie 0: Nombres ordinaux, nombres rationnels et nombres entiers

Cet exposé d'histoire des mathématiques, en deux parties, est une motivation et une présentation du Chapitre 0 de la partie 0 (pages 2 à 14) du livre de John Conway "On Numbers and Games" (1976, 2ème édition 2000).Nous partirons de la construction des nombres ordinaux de Georg Cantor (1895) donnée par Paul R. Halmos (1965) -- à la suite de John Von Neumann (1923) -- et de la construction des nombres réels par Edmund Landau (1927) -- à la suite de Richard Dedekink (1887) -- et présenterons leur généralisation par John Conway (1976)