The effect of z-binding yarns on the electrical properties of 3D woven composites

Electrical resistance monitoring (ERM) has been used to study the effect of the z-binding yarns on the initial electrical resistance (ER) and its change of three architectures of 3D woven carbon fibre composites namely (orthogonal “ORT”, layer-to-layer “LTL” and angle interlock “AI”) when tested in tension. Specimens are loaded in on-axis “warp” and off-axis “45°” directions. In-situ ERM is achieved using the four-probe technique. Monotonic and cyclic “load/unload” tests are performed to investigate the effect of piezo-resistivity and residual plasticity on resistance variation. The resistance increase for the off-axis loaded specimens (∼90%) is found to be higher than that of their on-axis counterparts (∼20%). In the case of cyclic testing, the resistance increase upon unloading is irreversible which suggests permanent damage presence not piezo-resistive effect. At the moment, it is difficult to obtain a direct correlation between resistance variation and damage in 3D woven composites due to the complexity of the conduction path along the three orthogonal directions, however this study demonstrates the potential of using ERM for damage detection in 3D woven carbon fibre-based composites and highlights the challenges that need to be overcome to establish ERM as a Structural Health Monitoring (SHM) technique for such material systems

Rubber Impact on 3D Textile Composites

A low velocity impact study of aircraft tire rubber on 3D textile-reinforced composite plates was performed experimentally and numerically. In contrast to regular unidirectional composite laminates, no delaminations occur in such a 3D textile composite. Yarn decohesions, matrix cracks and yarn ruptures have been identified as the major damage mechanisms under impact load. An increase in the number of 3D warp yarns is proposed to improve the impact damage resistance. The characteristic of a rubber impact is the high amount of elastic energy stored in the impactor during impact, which was more than 90% of the initial kinetic energy. This large geometrical deformation of the rubber during impact leads to a less localised loading of the target structure and poses great challenges for the numerical modelling. A hyperelastic Mooney-Rivlin constitutive law was used in Abaqus/Explicit based on a step-by-step validation with static rubber compression tests and low velocity impact tests on aluminium plates. Simulation models of the textile weave were developed on the meso- and macro-scale. The final correlation between impact simulation results on 3D textile-reinforced composite plates and impact test data was promising, highlighting the potential of such numerical simulation tools

Hijacking of the Pleiotropic Cytokine Interferon-γ by the Type III Secretion System of Yersinia pestis

Yersinia pestis, the causative agent of bubonic plague, employs its type III secretion system to inject toxins into target cells, a crucial step in infection establishment. LcrV is an essential component of the T3SS of Yersinia spp, and is able to associate at the tip of the secretion needle and take part in the translocation of anti-host effector proteins into the eukaryotic cell cytoplasm. Upon cell contact, LcrV is also released into the surrounding medium where it has been shown to block the normal inflammatory response, although details of this mechanism have remained elusive. In this work, we reveal a key aspect of the immunomodulatory function of LcrV by showing that it interacts directly and with nanomolar affinity with the inflammatory cytokine IFNγ. In addition, we generate specific IFNγ mutants that show decreased interaction capabilities towards LcrV, enabling us to map the interaction region to two basic C-terminal clusters of IFNγ. Lastly, we show that the LcrV-IFNγ interaction can be disrupted by a number of inhibitors, some of which display nanomolar affinity. This study thus not only identifies novel potential inhibitors that could be developed for the control of Yersinia-induced infection, but also highlights the diversity of the strategies used by Y. pestis to evade the immune system, with the hijacking of pleiotropic cytokines being a long-range mechanism that potentially plays a key role in the severity of plague

Investigation of the acqueous transmetalation of pi-allylpalladium with indium salt: the use of the Pd(OAc)2-TPPTS catalyst

\u3c0-Allylpalladium complexes could be generated in water by the palladium(0) water soluble catalyst prepared in situ from palladium acetate and TPPTS. These complexes were transmetalated with indium to react with benzaldehyde. The aqueous solution of Pd(0)(TPPTS)n could be reused without deterioration of the catalyst in the first and second recycling. The system proved to be efficient with primary and secondary allylic substrates. The stereochemical outcome of the allylation through umpolung of allylpalladium, was also studied using models with a restraint conformation

Estimating and understanding the efficiency of nanoparticles in enhancing the conductivity of carbon nanotube/polymer composites

Carbon nanotubes (CNTs) have been widely used to improve the electrical conductivity of polymers. However, not all CNTs actively participate in the conduction of electricity since they have to be close to each other to form a conductive network. The amount of active CNTs is rarely discussed as it is not captured by percolation theory. However, this amount is a very important information that could be used in a definition of loading efficiency for CNTs (and, in general, for any nanofiller). Thus, we develop a computational tool to quantify the amount of CNTs that actively participates in the conductive network. We then use this quantity to propose a definition of loading efficiency. We compare our results with an expression presented in the literature for the fraction of percolated CNTs (although not presented as a definition of efficiency). We found that this expression underestimates the fraction of percolated CNTs. We thus propose an improved estimation. We also study how efficiency changes with CNT loading and the CNT aspect ratio. We use this concept to study the size of the representative volume element (RVE) for polymers loaded with CNTs, which has received little attention in the past. Here, we find the size of RVE based on both loading efficiency and electrical conductivity such that the scales of “morphological” and “functional” RVEs can be compared. Additionally, we study the relations between particle and network properties (such as efficiency, CNT conductivity and junction resistance) and the conductivity of CNT/polymer composites. We present a series of recommendations to improve the conductivity of a composite based on our simulation results. Keywords: Carbon nanotube, Composites, Electrical conductivity, Representative volume element, Geometric modelin

High‐Sensitivity RFID Sensor for Structural Health Monitoring

Abstract Structural health monitoring (SHM) is crucial for ensuring operational safety in applications like pipelines, tanks, aircraft, ships, and vehicles. Traditional embedded sensors have limitations due to expense and potential structural damage. A novel technology using radio frequency identification devices (RFID) offers wireless transmission of highly sensitive strain measurement data. The system features a thin, flexible sensor based on an inductance‐capacitance (LC) circuit with a parallel‐plate capacitance sensing unit. By incorporating tailored cracks in the capacitor electrodes, the sensor’s capacitor electrodes become highly piezoresistive, modifying electromagnetic wave penetration. This unconventional change in capacitance shifts the resonance frequency, resulting in a wireless strain sensor with a gauge factor of 50 for strains under 1%. The frequency shift is passively detected through an external readout system using simple frequency sweeping. This wire‐free, power‐free design allows easy integration into composites without compromising structural integrity. Experimental results demonstrate the cracked wireless strain sensor's ability to detect small strains within composites. This technology offers a cost‐effective, non‐destructive solution for accurate structural health monitoring

Une approche en dissipation pour l’identification de propriétés matériaux hétérogènes à partir de mesures de champs

Une piste privilégiée pour l’identification rapide de comportements complexes ou très hétérogènes est l’emploi de mesures de champs (cinématiques, thermiques, etc.). De par leur richesse par rapport à des mesures ponctuelles classiques, ces mesures permettent d’envisager l’identification de lois d’évolution complexes sur la base de peu d’essais très hétérogènes. Plusieurs méthodes ont été proposées en ce sens, principalement en élasticité linéaire. Nous détaillons ici l’application de l’erreur en relation de comportement, en vue de l’identification de modèles élastiques linéaires. L’extension naturelle de l’erreur en relation de comportement, au travers d’une méthode de saut à la dissipation, est proposée pour l’identification de phénomènes dissipatifs. Des exemples de référence 2D concluent cette publication