Search results for "composite"
showing 10 items of 4584 documents
Moisture Absorption Effects on the Resistance to Interlaminar Fracture of Woven Glass/Epoxy Composite Laminates
2012
The influence of moisture absorption on the interlaminar fracture behaviour of 8/8 harness satin weave glass/epoxy composite was investigated. Two series of specimens with 0°/0° and 90°/90° predominant interfaces immersed in water for different duration were tested under double cantilever beam (DCB mode I), single leg bending (SLB mode I + II) and end notched flexural (ENF mode II) loadings. In general, the apparent flexural modulus: E, and the fracture toughness: G C, decrease with increasing moisture content. This effect is more remarkable if mode II participation is bigger. The value of G C measured on 90°/90° specimens reveals higher than that on 0°/0° ones, but the variation in G C is …
Carbon Fiber Composites Cured by γ-Radiation-Induced Polymerization of an Epoxy Resin Matrix
2008
The use of ionizing radiation in order to initiate polymerization of suitable monomers has found increased interest in the last two decades due to its several advantages. In this work, carbon fiber composites through gamma radiation polymerization of epoxy matrices have been produced for aerospace and advanced automotive applications. Composite samples were produced by irradiation at room temperature using different radiation doses and, as reference, thermal curing of the same epoxy resin formulations was also carried out. Furthermore, some irradiated samples were subjected to postirradiation thermal curing to complete the polymerization reactions. The properties of the cured materials were…
Anomalous water diffusion in epoxy/carbon nanoparticle composites
2019
Abstract Water absorption-desorption-resorption and swelling were studied for a DGEBA-based amine-cured epoxy resin filled with four types of carbon nanoparticles: multiwall carbon nanotubes (MWCNT), graphite nano-platelets (GnP), expanded graphite platelets, and carbon black. Nanocomposites are characterised by lower diffusivity (down to 20% for epoxy/GnP) and increased water sorption capacity compared to the neat epoxy. Anomalous water absorption and swelling of nanocomposites is finely described by the diffusion-relaxation model. The relaxation times, considered as quantitative indicators of changes in segmental mobility of the polymer, increased with addition of nanoparticles and decrea…
Thermo- and photo-modulation of exciplex fluorescence in a 3D spin crossover Hofmann-type coordination polymer
2018
[EN] The search for bifunctional materials showing synergies between spin crossover (SCO) and luminescence has attracted substantial interest since they could be promising platforms for new switching electronic and optical technologies. In this context, we present the first three-dimensional Fe-II Hofmann-type coordination polymer exhibiting SCO properties and luminescence. The complex {Fe-II(bpben)[Au(CN)(2)]}@pyr (bpben = 1,4-bis(4-pyridyl)benzene) functionalized with pyrene (pyr) guests undergoes a cooperative multi-step SCO, which has been investigated by single crystal X-ray diffraction, single crystal UV-Vis absorption spectroscopy, and magnetic and calorimetric measurements. The resu…
Local structure of ball-milled LaNi5 hydrogen storage material by Ni K-edge EXAFS
2010
Abstract Local structure of the nanostructured LaNi5 hydrogen storage alloys, prepared by ball-milling, has been studied using Ni K-edge extended X-ray absorption fine structure spectroscopy. Results indicate that the ball-milling up to 100 h results in the production of nanoparticles characterized by large atomic disorder and slightly reduced unit-cell volume, compared to the bulk LaNi5. High temperature annealing appears to help in partial recovery of atomic order in the ball-milled samples; however, long-time ball-milled samples retain large disorder even after the high temperature annealing. The results suggest that the large disorder and the reduced unit-cell volume might be causing a …
CO2 laser-induced structure changes in lead zirconate titanate Pb(Zr0.58Ti0.42)O3 sol–gel films
2003
Based on absorption spectra of lanthanum modified lead zirconate titanate Pb0.9La0.1(Zr0.65Ti0.35)O3 (PLZT10/65/35) ferroelectric ceramics an idea of local and selective treatment of lead zirconite titanate Pb(ZrXTi1−X)O3 (PZT) sol–gel film in the multi-layer structure by CO2 laser radiation was formulated. The possibility to obtain PZT perovskite film on the SiO2/Si substrate by irradiation with CO2 laser was shown experimentally. X-ray studies revealed the PZT perovskite structure ratio growth at the expenses of pirochlore structure with an increased power density of laser radiation.
Rheological, mechanical and morphological characterization of monopolymer blends made by virgin and photo-oxidized polypropylene
2021
In this work, monopolymer blends of virgin polypropylene and photo-oxidized polypropylene were prepare and characterized. The polypropylene samples were subjected to accelerated ageing to simulate the effects of outdoor exposure of polypropylene. After exposure, samples were pelletized and mixed with the same virgin polymer. The rheological, mechanical and morphological characterization was conducted on both the polymers and the blends. Both viscosity and mechanical properties decrease with increases in the content of recycled, photo-oxidized components and of the level of degradation of this component. In addition, the experimental data were compared with a model that takes into account bo…
Improvement of oxidation resistance of polymer-based nanocomposites through sonication of carbonaceous nanoparticles
2020
Abstract The work aim is focused on two different aspects: first, the investigation of the effect of extended ultra-sound-assisted treatment (us) of carbonaceous nanoparticles, such as carbon nanotubes (CNTs) and carbon black (CB), on their radical scavenging activity, and second, the investigation of the oxidative resistance of polymer-based nanocomposites, containing us-treated CNTs and CB. Particularly, the CNTs and CB have been subjected to us sonication for different time intervals and the performed analysis reveals that both kinds of nanoparticles show decreased average hydrodynamic diameters and large content of surface defects. Really, the increased content of CNTs and CB defects, a…
A stochastic shape and orientation model for fibres with an application to carbon nanotubes
2012
Methods are introduced for analysing the shape and orientation of planar fibres from greyscale images of fibrous systems. The sequence of image processing techniques needed for segmentation of fibres is described. The identified fibres were interpreted as deformed line segments for which two shape and two orientation parameters are estimated by the maximum likelihood method. The methods introduced are shown to perform quite well for simulated systems of deformed line segments with known properties. They were applied to TEM images of carbon nanotubes embedded in polycarbonate.
Acoustics of porous materials with partially opened porosity
2013
International audience; A theoretical and experimental study of the acoustic properties of porous materials containing dead-end (or partially opened) porosity was recently proposed by Dupont et al. The present article provides a description of partially opened porosity systems and their numerous potential applications in the general context of the study of porous materials, the classical models describing them, and the characterization techniques. It is shown that the dead-end pore effect can be treated independently and that the description of this effect can be associated with any acoustic model of porous media. Different theoretical developments describing the dead-end porosity effect ar…