Search results for "CERAMICS"
showing 10 items of 1599 documents
Mechanical properties of pultruded glass fiber reinforced plastic after freeze–thaw cycling
2012
The use of pultruded fiber-reinforced plastics in civil infrastructure requires the long-term prediction of their mechanical properties, which should be based on understanding and estimating the processes in the structure under action of aggressive environmental factors: humidity and freeze–thaw cycles. This article reports on results of short-term exposure to severe freeze–thaw cycling in the temperature range from –30°C to 20°C of polyester-based glass fiber reinforced plastic both dry and wet. The effect of freeze–thaw cycling of flat specimens cut from I-beam pultruded profile was estimated by use of three-point-bending tests and dilatometric investigation in the temperature range from…
Size effects in micro- and nanoscale indentation
2006
Abstract The indentation size effect (ISE) has been studied in single crystals, polycrystals and amorphous solids using the Vickers microhardness test. The ISE is clearly present in single crystals but is absent in fine-grained polycrystals. A size-dependent hardness for amorphous solids is observed only in the sub-micrometre surface layer. The behaviour of the ISE in single crystals for micro- and nanoindentation is compared. Estimates of the surface hardness are made by the extrapolation of the experimental hardness–indentation depth curves. The extrapolated hardness in the surface region reaches values corresponding to the theoretical shear strength. The results confirm the multifarious …
Scattering perspectives on nanostructural inhomogeneity in polymer network gels
2017
Abstract Scattering methods based on spatial and temporal contrast fluctuations in polymer-network gels, which originate from polymer-segmental density fluctuations, reveal rich insight into different types and levels of nanostructural inhomogeneity in these soft materials. Complementary contrasting as provided by light, neutron, and X-ray scattering allows such information to be obtained on nano- to micrometer length scales. On top of that, complementary use of static and dynamic scattering methods allows the interplay and effect of these inhomogeneities to be unraveled. This article interrelates a multitude of studies on the application of scattering techniques for analytical assessment o…
Sintering of Fe2NiO4 with an internal binder: a way to obtain a very dense material
2003
Abstract The coupled synthesis and sintering of Fe2NiO4 can be carried out from the calcination under air at high temperatures (>1200 °C) of precompacted (under 12 MPa) pellets of different mixtures: NiO/α-Fe2O3; NiO/α-Fe2O3/Fe; NiO/α-Fe2O3/Ni. The densest material is obtained at 1200 °C only from the following mixture: NiO (40 mol%), α-Fe2O3 (50 mol%) and Ni (10 mol%). Because the metallic nickel is very ductile, it is used as an internal binder in order to enhance the precompacting of the samples. Moreover, the role of nickel is to enhance the sintering reaction. This route leads to a final material of relative density close to 98±2%.
Strain mapping near a triple junction in strained Ni-based alloy using EBSD and biaxial nanogauges
2011
A key element for analyzing the crack initiation in strained polycrystalline alloys is the local quantification of the surface strain distribution according to the grain texture. Using electron backscattered diffraction, the local microstructure was determined to both localize a triple junction and deduce the local Schmid factors. Kernel average misorientation (KAM) was also used to map the areas of defect concentration. The maximum principal strain and the in-plane shear strain were quantified using the biaxial nanogauge. Distortions of the array of nanodots used as spot markers were analyzed near the triple junction. The crystallographic orientation and the surface strain were then invest…
Mechanical Properties of High-Density Polyethylene/Chlorinated Polyethylene Blends
2004
Results of experimental investigation of mechanical properties of high-density polyethylene (HDPE)/chlorinated polyethylene (CPE) blends in tension are reported. The specimens of pure HDPE, CPE, and nine types of HDPE/CPE blends, with different component ratios at 10 wt.% intervals, are examined. The features of the stress-strain curves obtained are discussed. Data on the influence of blend composition on the elastic modulus, yield stress, breaking stress, and ultimate elongation are obtained. The results of investigations into the creep behavior are also presented. It is found that the creep compliance obeys the power law of creep with coefficients depending on blend composition.
Longitudinal Flexure as a Method for Determining the Flexural Strength of Composite Materials
2004
A method is presented for determining the flexural strength of composites from tests on pinned specimens in axial compression. This scheme is close to the so-called Euler buckling model, but the load is applied eccentrically, and the bar is bent practically from the beginning of loading. An analytical model is proposed for calculating the flexural stress in longitudinal flexure of a thin bar in the case of large displacements. The problem is solved in elliptic integrals of the first and second kinds. The analytical model shows an excellent agreement with experiments. The results obtained are compared with experimental tension data. A device is also designed for testing composite bars in lon…
Study and comparison of interaction parameters and phase behavior of epoxy/polystyrene and epoxies copolymer polystyrene-b-poly(methyl methacrylate) …
2008
Thermodynamic studies in terms of phase separation behavior and interaction parameters, in mixtures of epoxy resins (thermoset materials) with thermoplastic additives, consisting of polystyrene (PS) or polystyrene-b-poly(methyl methacrylate) P(S-MMA) (with small proportion of MMA), have been carried out. It can be confirmed that the solubility of P(S-MMA) is an improvement on that of PS, with the prepolymer epoxy resins. Moreover, the interaction parameters are positive at temperatures in which phase separation is observed, but negative at temperatures in which the phase separation window disappears, in the corresponding phase diagram. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engine…
Dislocation interaction with C in α-Fe: a comparison between atomic simulations and elasticity theory
2008
International audience; The interaction of C atoms with a screw and an edge dislocation is modelled at an atomic scale using an empirical Fe-C interatomic potential based on the Embedded Atom Method (EAM) and molecular statics simulations. Results of atomic simulations are compared with predictions of elasticity theory. It is shown that a quantitative agreement can be obtained between both modelling techniques as long as anisotropic elastic calculations are performed and both the dilatation and the tetragonal distortion induced by the C interstitial are considered. Using isotropic elasticity allows to predict the main trends of the interaction and considering only the interstitial dilatatio…
Modeling the influence of mineral content and porosity on ultrasound parameters in bone by using synthetic phantoms
1999
Model composite media − 10×15×80 mm3 bone tissue phantoms based on an epoxy resin with fillers—were made to study the influence of porosity and mineral content on ultrasound velocity and attenuation. The pores were simulated by ∼ 1 mm3 particles of a soft rubber, while the mineral content was imitated by a mineral residue of natural bone obtained by burning and grinding. The porosity and mineral content were varied in the range of 0–70% by volume with a step of 10%. The velocity, attenuation, and prevalent frequency of ultrasound were measured by the pulse transition method, using transducers with nominal frequencies 0.1, 0.2, 0.5, and 1.0 MHz. It was experimentally found that the ultrasoun…