The orientational ordering taking place upon deforming uniaxially elastomeric networks is detected and quantified by infrared dichroism. The type of information gained from orientational measurements is discussed in the case of pure networks and also in rubber composites. This information, compared to that obtained from mechanical measurements, provided a better understanding of the molecular processes involved in rubber reinforcement. 相似文献
In the paper, the WL quasi-exact reinforcement theory of fibrous polymeric composites is improved. An optimum compatibility condition related to the transverse shear problem for a unit cell, which brings solutions closest to reality, is derived. This condition is formulated in the form of a linear combination of maximum radial and circumferential displacements. Optimum coefficients of this combination are determined by comparing analytical and numerical solutions for a test specimen in the form of a rectangular thin plate, which is in a plane strain state and is subject to selected loading schemes. The analytic solutions are obtained for a homogenized material by using the WL reinforcement theory. The numerical solutions are found for an actual heterogeneous composite material by using the finite-element method, and they verify the WL reinforcement theory, in particular, the admissibility of Hills assumption. An analysis performed for two composite materials shows that the improved WL reinforcement theory gives adequate displacement fields.Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 1, pp. 79–92, January–Febrauary, 2005. 相似文献
AISI 316L stainless steel was laser surface treated with different compositions of Si3N4 and Ti under various laser-processing parameters to improve its surface hardness through reinforcement of Ti-based silicides. The laser-treated regions exhibited improved surface hardness (250–1000 HV), variations in the surface morphology (smooth and bowl like) and presence of cracks and pores depending upon the Si3N4–Ti composition and laser-processing parameters. The study shows that when the Si3N4–Ti composition is 75–25 wt% and laser parameters are 1.5 kW laser power and 1.0 m min−1 scan speed, a laser-treated region with high hardness of about 800 HV and smooth surface morphology as well as free from pores and cracks is observed. The X-ray diffractometer (XRD) and Energy-Dispersive Spectroscopy (EDS) analyses show that the laser surface-treated region has reinforced phase of Ti5Si3 and retained austenitic structure. The reinforced phase gives rise to very high hardness (or wear resistance) and also a corrosion resistance. 相似文献
The fabrication of nanocomposites of low‐density polyethylene (LDPE), one of the world's most widely used polymers, and cellulose nanocrystals (CNCs), which represent the world's most abundant bio‐based nanofiller, is reported. While the hydrophobic polymer and the hydrophilic filler seem to be intrinsically incompatible, this article shows that it is possible to kinetically trap homogeneous nanocomposites by a templating approach. An organogel is first prepared by exchanging the solvent of an aqueous CNC dispersion against acetone, impregnating the resulting organogel, in which the CNCs form a percolating network with a hot LDPE solution in toluene, and compression‐molding the resulting materials into thin films. At a filler content of 7.6% v/v, the resulting materials display a three‐ to four‐fold increase in strength and stiffness compared with the neat LDPE, which confirms that the CNC network could be largely maintained. It is also possible to reprocess these nanocomposites and dilute them with LDPE using conventional melt‐processing techniques.
This paper reports on the physical and mechanical properties of the thermoplastic sago starch/kenaf fibre (TPSS/KF) composite. The composite was prepared through a compression molding technique at varying fibre contents of 0, 10, 20 and 30 wt.%, whilst the effect of the fibres incorporation was evaluated by physical and mechanical tests, as well as morphological analysis. Reduction of moisture content and denser composite were achieved with a higher fibre content. Meanwhile, the water absorption of the composite was lower than the thermoplastic with an increase in the kenaf fibre loading. Tensile testing improved strength and modulus with the increase of fibres content until an optimum was reached at 30 wt.% of fiber loading. Morphological analysis showed good wetting between the polymer matrix and fibres that provided the tensile improvement. 相似文献
TiB2 reinforced iron-based composite coatings can be fabricated on the mild steel substrate with a powder mixture of Ti and B4C by plasma transferred arc (PTA) powder surfacing process. Characterizations of the TiB2 reinforcements in the coated surface were investigated in this paper. The experimental work enables the following findings to be obtained: (i) acicular shaped and blocky formed TiB2 phases could be synthesized in situ using PTA powder surfacing process in the iron-based composite coating. (ii) Gradient distributions of TiB2 reinforcements appeared in the composite coating from both the vertical and horizontal direction of the coating's cross-section. Significant changes of the size, shape and volume fraction for TiB2 particles appeared in different regions of the surface coating, due to the effects of the dilution rate and mass density. (iii) Values of coating dilution could have profound impacts on the characterization of TiB2 reinforcements in the coated surfaces. With the increase of coating dilution, TiB2 grain tends to be acicular shaped at the edge of the surface coating, while it remains to be granular formed in the center of the composite coating. 相似文献