Search results for "Composites"
showing 10 items of 1905 documents
Time-resolved X-ray microtomographic measurement of water transport in wood-fibre reinforced composite material
2016
Natural fibre composites are prone to absorb moisture from the environment which may lead to dimensional changes, mold growth, degradation of mechanical properties or other adverse effects. In this work we develop a method for direct non-intrusive measurement of local moisture content inside a material sample. The method is based on X-ray microtomography, digital image correlation and image analysis. As a first application of the method we study axial transport of water in a cylindrical polylactic acid/birch pulp composite material sample with one end exposed to water. Based on the results, the method seems to give plausible estimates of water content profiles inside the cylindrical sample.…
Dependence of the Lattice Parameter of Magnesium Oxide on Crystallite Size
1966
Lattice parameters were measured on MgO specimens prepared in air between 450° and 1200°C. The lattice parameter, a, decreases with increase in preparation temperature, Tp, and with increase in crystallite size. A hydroxide layer is present on the MgO particles. If MgO is prepared in vacuum, a increases as Tp increases and as crystallite size, D, increases. It is concluded that a dilatant volume stress is imposed by the hydroxide layer. It is also shown that the oxide surface reactivity toward water is linked to the deviation from perfect order ensuing from low preparation temperatures.
The β-relaxation amplitudes for a dipolar hard sphere glass
1998
Abstract The β-relaxation amplitudes h m l , l ′ ( q ) for a dipolar hard sphere model are calculated in the diagonalization approximation up to l =1. The relevance to experimental difficulties to detect the characteristic β-relaxation minimum in dielectric loss measurements is discussed. Additionally, the microscopic nature of the β-relaxation of the rotational components is investigated by discussing the amplitudes in real space at different temperatures and densities.
IMPLICIT MESH DISCONTINUOUS GALERKIN FOR VARIABLE ANGLE TOW MULTILAYERED PLATES
2018
This works presents a novel computational scheme for variable angle tow (VAT) multilayered plates [1]. The characteristic features of the proposed scheme are the combined use of a discontinuous Galerkin (dG) formulation and an implicitly defined mesh. The formulation is based on the principle of virtual displacements (PVD) and the Equivalent Single Layer (ESL) assumption for the mechanical behavior of the VAT plates [2]. The problem is first placed within the dG framework by suitably introducing an auxiliary variable and by rewriting the set of equations governing ESL VAT plates as a firstorder system of differential equations. Following Arnold et al.[3] and by introducing suitably defined …
High-fidelity analysis of multilayered shells with cut-outs via the discontinuous Galerkin method
2021
Abstract A novel numerical method for the analysis of multilayered shells with cut-outs is presented. In the proposed approach, the shell geometry is represented via either analytical functions or NURBS parametrizations , while generally-shaped cut-outs are defined implicitly within the shell modelling domain via a level set function . The multilayered shell problem is addressed via the Equivalent-Single-Layer approach whereby high-order polynomial functions are employed to approximate the covariant components of the displacement field throughout the shell thickness. The shell governing equations are then derived from the Principle of Virtual Displacements of three-dimensional elasticity an…
A family of weakest link models for fiber strength distribution
2007
It is well known that the most widely used distribution function for fiber tensile strength, the two-parameter Weibull distribution, does not always adequately describe the experimentally observed fiber strength scatter and the strength dependence on fiber length. To remedy this discrepancy, modifications of the Weibull distribution have been proposed that, while providing a good empirical fit to the strength data, sometimes lack the theoretical appeal of the weakest link models. We derive a family of weakest link models based on the assumption of a two-stage failure process incorporating explicitly the probabilities of flaw initiation and the fiber fracture due to the largest flaw (i.e. th…
Urbach absorption edge of silica: reduction of glassy disorder by fluorine doping
2004
Abstract The vacuum-ultraviolet fundamental absorption edge (‘Urbach edge’) of four types of synthetic silica glasses, ‘wet’, ‘dry’, and doped by 570 and 6010 ppm wt. fluorine, was studied in the absorption coefficient range (1 cm−1–500 cm−1) at room temperature. The absorption edge has exponential form in agreement with the Urbach’s rule. The well-documented increase of vacuum-ultraviolet transparency upon fluorine doping is due to a steeper absorption edge (shorter ‘Urbach tail’) as compared to undoped silicas. The increase of the edge slope in F-doped silica occurs already the lower dopant concentration (570 ppm), the slope does not increase further in the 6010 ppm doped glass. These fin…
In VitroRelease of Local Anaesthetic and Anti-Inflammatory Drugs from Crosslinked Collagen Based Device
2012
The drug delivery systems that are the object of this article take the form of a hydrophilic matrix (collagen or crosslinked collagen) containing a drug. These devices can be used as The model active agents, were chosen from the range of local anaesthetics (lidocaine hydrochloride), anti-inflammatory (diclofenac sodium salt) and antioxydant (caffeic acid). Whatever the drug affinity for water, in the first time of the experiments, the release appears to be systematically delayed when the matrix is crosslinked. For lidocaine hydrochloride based systems, as the amount of drug increases in the matrix, the high gap concentration between the matrix and the buffer solution promote the diffusion a…
Dense drug-eluting biodegradable Fe-Ag nanocomposites
2021
Abstract Biodegradable metals in orthopedics are aimed to eliminate secondary the surgical intervention for implant removal, and thus improve patient compliance, reduce surgery costs and the risk of infections. In addition, biodegradable implants could be loaded with different drugs to prevent the growth of pathogens and the development of bone infections, kill remaining cancer cells after tumor resection or stimulate bone regeneration. However, drugs undergo thermal decomposition under the conditions of conventional metal fabrication processes. In this work, we describe the fabrication of a dense drug-eluting biodegradable Fe-Ag nanocomposite containing 10 vol% of Ag and loaded with the an…
X-ray crystallography-promoted drug design of carbonic anhydrase inhibitors.
2015
1-N-Alkylated-6-sulfamoyl saccharin derivatives were prepared and assayed as carbonic anhydrase inhibitors (CAIs). During X-ray crystallographic experiments an unexpected hydrolysis of the isothiazole ring was evidenced which allowed us to prepare highly potent enzyme inhibitors with selectivity for some isoforms with medical applications.