Search results for "strength"
showing 10 items of 2415 documents
Strong optical nonlinearities in gallium and indium selenides related to inter-valence-band transitions induced by light pulses
1997
A nonlinear optical effect is shown to occur in gallium and indium selenides at photon energies of the order of 1.5 eV. It corresponds to transitions from a lower-energy valence band to the uppermost one when a nonequilibrium degenerate hole gas is created in the latter by a laser pulse. This inter-valence-band transition is allowed by crystal symmetry. Its oscillator strength is estimated through the $f$-sum rule and turns out to be about two orders of magnitude higher than that of the fundamental transition. The intensity of this effect is stronger when the pump pulse photon energy is close to that of the inter-valence-band transition; a condition that can be fulfilled only in indium sele…
Simplified Model for Compressive Behavior of Concrete Columns Strengthened by Steel Angles and Strips
2010
This paper presents an analytical model to determine the compressive response of concrete members, having a square transverse cross section and reinforced with steel angles at the corners and steel strips connecting the steel angles. The model evaluates the effects of transverse strips and steel angles on confinement pressures, including strength and buckling phenomena. Compressive response was evaluated in cases of directly and indirectly loaded elements. The data produced correlate well with available experimental data.
Effect of hydroxyapatite concentration and size on morpho-mechanical properties of PLA-based randomly oriented and aligned electrospun nanofibrous ma…
2019
The growing demand for nanofibrous biocomposites able to provide peculiar properties requires systematic investigations of processing-structure-property relationships. Understanding the morpho-mechanical properties of an electrospun scaffold as a function of the filler features and mat microstructure can aid in designing these systems. In this work, the reinforcing effect of micrometric and nanometric hydroxyapatite particles in polylactic acid-based electrospun scaffold presenting random and aligned fibers orientation, was evaluated. The particles incorporation was investigated trough Fourier transform infrared spectroscopy in attenuated total reflectance. The morphology of the nanofibers …
Recycled Polycarbonate Based Nanocomposites
2013
Post-consumer polycarbonate (RPC) blends with various amounts (5, 10, 30 wt. %) of ethylene vinyl acetate copolymer (EVAc) are investigated as potential nanocomposite matrices. At EVAc weight content of 10 wt.% maximum tensile strength σM and impact strength AI increase is observed in comparison to neat RPC. Addition of EVAc, however, reduces resistance to creep as well as decrease thermal stability of the investigated compositions. Addition of montmorillonite nanoclay (MMT), however, allows increase modulus of elasticity E and yield strength σY of the investigated RPC blend with 10 wt. % of EVAc. Besides it creep resistance and thermal resistance of the investigated system is increased to …
Processing-structure-property relationships of electrospun PLA-PEO membranes reinforced with enzymatic cellulose nanofibers
2020
Abstract Three different solvent mixtures were used to prepare electrospun membranes based on polylactic acid (PLA), polyethylene oxide (PEO) and enzymatic cellulose nanofibers (CNF). The materials were characterized from a morphological, spectroscopic, mechanical and rheological point of view. Furthermore, swelling test were performed in order to assess the water uptake of each sample. The results put into evidence that the choice of the solvents affects the structure and the properties of the membranes. Among the protocols tested, using chloroform/acetone/ethanol mixture was found to allow a high degree of CNF dispersion and a good electrospinnability of polymer solutions. These features …
A probabilistic model of the tensile strength of a UD flax-fabric-reinforced polymer composite
2016
In order to fully realize the efficiency of bast fibers or their yarns as reinforcement of polymer composites, they should be aligned. Tensile strength of such composites in the direction of reinforcement has been found to exhibit size effect commensurable with that of unidirectionally reinforced (UD) composites with inorganic fibers, necessitating a probabilistic modeling approach. Strength distribution of a polymer matrix composite reinforced with aligned twisted bast fiber yarns is considered allowing for the strength scatter of elementary fibers, the presence of defects in the form of adjacent fiber breaks, and twist of the yarns. The model is applied to predicting the strength of flax/…
In-situ nano-silica deposition and air-abrasion with Bioglass 45S5 or aluminium oxide: Effects on methacrylate bonding to yttria-tetragonal zirconia …
2015
This study aimed at assessing the bonding performance after water storage (24 h/6-month) of a methacrylate-based cement applied onto Yttria-Tetragonal Zirconia Polycrystal(Y-TZP) pre-treated using an innovative in-situ silica nanoparticle deposition method and/or air-abrasion with Bioglass 45S5 (BAG) or aluminium oxide (AlO). Pre-sintered blocks of Y-TZP were coated with nano-silica using an experimental in-situ deposition method or used as received (control/silica-free). Air-abrasion was performed with AlO or BAG particles both on silica-coated and control Y-TZP specimens. All the specimens were then analysed using SEM– EDX. Further specimens were treated as described above, bonded using a…
Influence of sodium bicarbonate treatment on the aging resistance of natural fiber reinforced polymer composites under marine environment
2019
Abstract Aim of the current study is to investigate how an innovative and eco-friendly chemical treatment based on sodium bicarbonate solution (10 wt%) can improve the aging resistance in marine environment of epoxy based composites, reinforced with flax and jute fibers. To this scope, treated and untreated fiber reinforced composites were manufactured through vacuum infusion technique. The resulting composites were then exposed to salt-fog spray conditions up to 60 days, according to ASTM B117 standard. The assessment of their durability was made by means of tensile, flexural quasi-static tests and Charpy impact tests. Furthermore, the water uptake evolution of each composite was monitored…
Pinned hybrid glass-flax composite laminates aged in salt-fog environment: Mechanical durability
2019
The aim of the present paper is to study the mechanical performance evolution of pinned hybrid glass-flax composite laminates under environment aging conditions. Hybrid glass-flax fibers/epoxy pinned laminates were exposed to salt-spray fog environmental conditions up to 60 days. With the purpose of assessing the relationship between mechanical performances and failure mechanisms at increasing aging time, single lap joints at varying joint geometry (i.e., hole diameter D and hole distance E from free edge) were characterized after 0 days (i.e., unaged samples), 30 days, and 60 days of salt-fog exposition. Based on this approach, the property&ndash
New concept in bioderived composites: Biochar as toughening agent for improving performances and durability of agave-based epoxy biocomposites
2021
Biocomposites are increasingly used in the industry for the replacement of synthetic materials, thanks to their good mechanical properties, being lightweight, and having low cost. Unfortunately, in several potential fields of structural application their static strength and fatigue life are not high enough. For this reason, several chemical treatments on the fibers have been proposed in literature, although still without fully satisfactory results. To overcome this drawback, in this study we present a procedure based on the addition of a carbonaceous filler to a green epoxy matrix reinforced by Agave sisalana fibers. Among all carbon-based materials, biochar was selected for its environment…