Fabrication and Characterization of Solid Composite Yarns from Carbon Nanotubes and Poly(dicyclopentadiene)

In this report, networks of carbon nanotubes (CNTs) are transformed into composite yarns by infusion, mechanical consolidation and polymerization of dicyclopentadiene (DCPD). The microstructures of the CNT yarn and its composite are characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and a focused ion beam used for cross-sectioning. Pristine yarns have tensile strength, modulus and elongation at failure of 0.8 GPa, 14 GPa and 14.0%, respectively. In the composite yarn, these values are significantly enhanced to 1.2 GPa, 68 GPa and 3.4%, respectively. Owing to the consolidation and alignment improvement, its electrical conductivity was increased from 1.0 × 105 S/m (raw yarn) to 5.0 × 105 S/m and 5.3 × 105 S/m for twisted yarn and composite yarn, respectively. The strengthening mechanism is attributed to the binding of the DCPD polymer, which acts as a capstan and increases frictional forces within the nanotube bundles, making it more difficult to pull them apart.

EXPERIENCE OF D. HOUSKNEСHT DIAGRAM FOR IMPACT ASSESMENT OF CONSOLIDATION AND CEMENTATION ON POROSITY OF THE LOWER-MIDDLE JURASSIC SANDSTONES OF THE NYUROLKA DEPRESSION AND THE KOLTOGOR-URENGOY MEGATROUGH

Using D. U. Hausknecht diagram, the degree of impact of authigenic cementation, pressure solution and mechanical consolidation on the reduction of porosity and intergranular volume of the Lower - Middle Jurassic sandstones in the territory of the Tomsk region was determined. Sandstones of the Nadoyakha (Lower Toarcian – Lower Aalenian, bed Yu15), Vymskoye (Lower Bajocian, beds Yu11–Yu14), Leontievskiy (Lower-Upper Bajocian, beds Yu8–Yu10) and Malyshevka (Upper Bajocian – Bathonian, beds Yu3–Yu6) were analyzed horizons penetrated by a number of wells in western regions of the Nyurolka depression and the southern part of the Koltogor-Urengoy megatrough in the depth interval 2702–3326 m. It was found that the reduction in the intergranular volume of studied rocks is associated not only with their genesis, material composition, and structural and textural features, but also with the amount, type and composition of cement. It was revealed that the main factor influencing the reduction of the primary volume of the pore space of terrigenous rocks to a depth of ~ 2900–3000 m is the authigenic cementation, and below 3000 m the leading role is played by mechanical consolidation and dissolution of detrital grains under pressure. For Late Toarсian-Aalenian sandstones in the studied areas, the contribution of the factor of mechanical consolidation and pressure solution on the reduction of the primary intergranular volume was 38–53%, and for sandstones of the Bajocian – 20–30%. For the latter, the share of authigenic cementation was 24–56%. The work also considers circumstances that limit this method and possibilities of its application for other types of rocks.

Experimental and analytical investigations of volume change behaviour of saturated expansive soils in oedometer test

The chemical and mechanical behaviours of saturated bentonite were experimentally and analytically investigated. A series of oedometer tests on saturated bentonite was conducted. By replacing the cell fluid during the oedometer test, one-dimensional osmotic consolidation and swelling behaviour were observed. The experimental results were simulated numerically using a constitutive model by considering the influence of electrochemical phenomena of clay mineral crystals on the macrostructural behaviour. It was concluded that the typical mechanical swellability of water-saturated bentonite in oedometer test is affected by a positive dilatancy behaviour due to the lower shear strength. After the osmotic consolidation test, a lateral contraction of the specimen in the oedometer was observed; this affected the compressibility during the subsequent mechanical consolidation. It was also concluded that the concentration of Na+ in the pore fluid affects the specific mechanical properties of bentonite.

Effect of mechanical consolidation on adhesion mechanism of hybrid non-woven Alfa fibers reinforced unsaturated polyester composite

Vibrational analysis based on FTIR measurements were performed on hybrid non-woven Alfa fibers reinforced unsaturated polyester composite (HNWAFRUP) and its constituents. The reinforcement was made up of Alfa and wool fibers in the relative volume fractions ratio 4:1. These non-woven fibers sheet were consolidated mechanically by means of the needle punching. This study revealed that the increase of passages numbers in this device allowed the separation of the Alfa fibers and the reduction of the lignin’s component in these fibers which decreased its hydrophilic character. Chemical reactions between wool and Alfa fibers were based mainly on the appearance of new vibrations originating from wool fibers in the reinforcement. Adhesion mechanism between the matrix and the reinforcement was established by chemical bonds formed by secondary bonding. Tensile testing performed on this composite revealed the enhancement of its mechanical properties attributed to a less fiber to fiber contact of wool fibers. Nevertheless, the decrease of its specific Young’s modulus revealed the mechanical consolidation effect on Alfa fibers/matrix adhesion.Â