Ski Boot Soles Based on a Glass Fiber/Rubber Composite with Improved Grip on Icy Surfaces

Abstract A study on the effect of glass fibers/rubber composites on the grip on ice has been conducted in order to develop new materials for ski boot soles with increased grip in winter environments. The study has been conducted analyzing the friction of a composite material and of a ski boot sole containing an insert made of the composite material and comparing the results with those obtained using rubber and a thermoplastic elastomer. The analysis of the morphology of the composite surface, by Scanning Electron Microscopy, shows a homogenous distribution of glass fibers of approximately 10 μm of diameter in the rubber matrix. Moreover, the measure of the contact angle shows that the composite material has a higher water repellency compared to the rubber matrix. The measure of the coefficient of friction indicates a significant effect of the glass fibers on the grip on icy surfaces. The increased grip can be ascribed to the stiffness of the glass fibers that are able to have a mechanical grip on the ice surface and to the increased contact angle and water repellency of the composite that decrease the formation of a water layer below the sole

Managing heat phenomena in epoxy composites production via graphenic derivatives: synthesis, properties and industrial production simulation of graphene and graphene oxide containing composites

A commercial two-components epoxy resin formulation was successfully modified by adding graphene and related materials (GRMs) and the effect of these nanofillers was assessed on their thermomechanical properties as well as on the simulation of their industrial application for the production of thick composites objects with interesting results. GMRs were added in different concentrations in order to improve thermo-mechanical properties of the nano-composite thermoset. Different dispersion methods were taken into account in order to produce stable long-lasting dispersion of the GRMs, that can withstand a commercial shelf life. Addition of the GRMs improves the glass transition temperature of the nanocomposite up to 20 °C with respect to the plain commercial formulation, and both stress and elongation at break increase up to almost 4 times the original values. Moreover, the industrial curing of some of the more promising modified resins was computer-simulated when the two-components resins are used to produce a carbon-fibre reinforced thick composite beam. Simulation results show that some of the applied GRMs helps reducing or even completely preventing the overheat phenomena that are well renown to induce significant thermal stresses negatively affecting the final object performances. These interesting effects would contribute reducing the time required for a single industrial production cycle, since no time for overheat dispersion is required, thus helping increasing the production rate

Microstructure, tensile and fatigue properties of AA6061/20vol.%Al2O3p Friction Stir Welded joints

Metal matrix composites reinforced with Al2O3 particles combine the matrix properties with those of the ceramic reinforcement, leading to higher stiffness and superior thermal stability with respect to the corresponding unreinforced alloys. However, their wide application as structural materials needs proper development of a suitable joining processes. The present work describes the results obtained from microstructural (optical and scanning electron microscopy) and mechanical evaluation (hardness, tensile and low-cycle fatigue tests) of an aluminium alloy (AA6061) matrix composite reinforced with 20 vol.% fraction of Al2O3 particles (W6A20A), welded using the friction stir welding process. The mechanical response of the FSW composite was compared with that of the base material and the results were discussed in the light of microstructural modifications induced by the FSW process on the aluminium alloy matrix and on the ceramic reinforcement. The FSW reduced the size of both particles reinforcement and aluminium grains and also led to overaging of the matrix alloys due to the frictional heating during welding. The FSW specimens, tested without any post-weld heat treatment or surface modification showed lower tensile strength and higher elongation to failure respect to the base material. The low-cycle fatigue life of the FSW composite was always lower than that of the base material, mainly at the lower strain-amplitude value. The cyclic stress response curves of the FSW composite showed evidence of progressive hardening to failure, at all cyclic strain-amplitudes, while the base material showed a progressive softening

Caratterizzazione microstrutturale e meccanica di giunti in composito AA6061/20%vol. Al2O3 ottenuti mediante Friction Stir Welding

Oltre agli studi indirizzati alla ottimizzazione dei processi di produzione dei compositi a matrice metallica (CMM), la ricerca tecnologica tende ora a indirizzarsi verso i processi di trasformazione degli stessi, per l’ottenimento di componenti affidabili e ad elevate prestazioni. In relazione a questo aspetto sono stati pubblicati molti studi riguardanti sia i processi di lavorabilità, per deformazione plastica e per asportazione di truciolo, che di saldatura. Sembra, inoltre, che la maggior parte dei procedimenti di saldatura adatti alle leghe monolitiche sia applicabile anche ai corrispondenti CMM, seppure con una maggiore cautela e con la necessità di una più accurata messa a punto dei parametri di saldatura, sia nei processi di saldatura in fase liquida che solida. I processi di saldatura per fusione inducono nei CMM i tipici difetti riscontrabili anche nelle corrispondenti leghe monolitiche. Si aggiungono inoltre problematiche ulteriori, connesse alla presenza del rinforzo: possibili reazioni chimiche tra matrice e rinforzo, con formazione di fasi fragili e indesiderate all’interfaccia e/o nella matrice; segregazione del rinforzo nelle zone interdendritiche, con conseguente diminuzione locale di duttilità; maggiore presenza di porosità da gas, poichè questi risultano meno facilmente eliminabili dal metallo fuso, per la tendenza delle particelle di rinforzo ad aderire alla superficie delle bolle di gas, rallentandone la risalita. I processi di saldatura allo stato solido applicabili ai CMM sono principalmente la saldatura per diffusione (Diffusion Bonding) e la saldatura per attrito, con la più recente e promettente variante del processo di Friction Stir Welding (FSW). Diversi studi effettuati su leghe di alluminio saldate mediante FSW hanno evidenziato che nel cordone di saldatura non si ha un significativo decremento delle proprietà meccaniche, rispetto al metallo base. L’obiettivo di questo lavoro è stato di valutare l’effetto della saldatura FSW sia sulla microstruttura che sulle proprietà meccaniche a trazione e fatica del composito a matrice in lega AA6061 rinforzata con il 20% in vol. di particelle di Al2O3 (di produzione Duralcan). Le osservazioni microstrutturali, condotte mediante microscopia ottica ed elettronica in scansione hanno evidenziato, nella zona saldata, frammentazione ed arrotondamento delle particelle di rinforzo, oltre ad un ingrossamento dei precipitati della matrice. Le prove di trazione monoassiale, condotte secondo normativa ISO/TTA2-9, hanno mostrato una riduzione della resistenza a trazione pari a circa il 28% ed una aumento di circa il 50% dell’allungamento a rottura del CMM saldato. Le prove di fatica oligociclica, condotte secondo normativa ASTM E606, hanno mostrato una diminuzione delle prestazioni del materiale saldato in tutto l’intervallo considerato (ampiezza di deformazione totale da 0.3% a 1%) ed una forte dispersione nei risultati, sia per il materiale saldato che per il CMM base

Effect of surface laser melting on microstructure and mechanical properties of the rare earth rich Mg alloy EV31A

The effect of surface laser melting on a rare earth rich magnesium alloy (Mg-Nd2.8-Gd1.5-Zr0.5-Zn0.2) was studied. Samples extracted from sand cast plates were surface laser melted (SLM) using 3.3 kW diode laser, then heat treated according to standard T6 conditions. Microstructural characterization on cross-sections of the SLM specimens allowed to identify four different areas: the remelted zone (RZ), mainly composed by fine grained equiaxed microstructure; the transition zone (TZ), consisting of columnar grains; the heat affected zone (HAZ), characterized by the partial dissolution of second phases and eutectic compound; the base material (BM). The T6 heat treatment after LSR induced a substantial grain growth in the RZ, resulting in a decrease of tensile properties in comparison to the T6 heat-treated alloy not subjected to laser remelting, despite substantially similar Brinell hardness values were registered

Deposition of Plasma-Polymerized Polyacrylic Acid Coatings by a Non-Equilibrium Atmospheric Pressure Nanopulsed Plasma Jet

International audienc

Biomimetic Action of Zinc Hydroxyapatite on Remineralization of Enamel and Dentin: A Review

Biomimetic zinc–carbonate hydroxyapatite technology was developed to realize materials that mimic the natural hydroxyapatite of enamel and dentin and possess good activity in terms of affinity to adhere to these biological tissues. The chemical and physical characteristics of this active ingredient allows the hydroxyapatite itself to be particularly similar to dental hydroxyapatite, enhancing the bond between biomimetic hydroxyapatite and dental hydroxyapatite. The aim of this review is to assess the efficacy of this technology in terms of benefits for enamel and dentin and reduction of dental hypersensitivity. Materials and methods: A literature search (Pubmed/MEDLINE and Scopus) of articles from 2003 to 2023 was conducted to analyze studies focused on the use of zinc-hydroxyapatite products. Duplicates were eliminated from the 5065 articles found, leaving 2076 articles. Of these, 30 articles were analyzed based on the use of products with zinc–carbonate hydroxyapatite in these studies. Results: 30 articles were included. Most of the studies showed benefits in terms of remineralization and prevention of enamel demineralization in terms of occlusion of the dentinal tubules and reduction of dentinal hypersensitivity. Conclusion: Oral care products such as toothpaste and mouthwash with biomimetic zinc–carbonate hydroxyapatite were shown to provide benefits according to the aims of this review