Effective medium theories for the optical properties of three-component composite materials

Based on the research of Niklasson et al. [Appl. Opt. 20, 26-30 (1981)], two effective medium theories, namely, the Maxwell-Garnett and the Bruggeman, for two-component systems are directly extended to three-component systems, and so theories for many-component systems can be obtained further. Note that one of these theories was obtained by Wood and Ashcroft [Philos. Mag. 35, 269-280 (1977)] and Stroud and Pan [Phys. Rev. B 17, 1602-1610 (1978)] by different or similar methods. The improved theories are employed in the calculation of the spectral reflectance of three samples of electrolytic colored anodic aluminum oxide film (Au-Cu-Al(2) O(3) and Ag-Cu-Al(2) O(3)), and the results are compared with the experimental results.     

Droplet orientation and optical properties of polymer dispersed liquid crystal composite films

The electro-optic and thermo-optic properties of polymer dispersed liquid crystal (PDLC) films have been investigated. The effects of applied voltage and temperature on liquid crystal droplet morphology and its transmission characteristics were studied. Threshold voltage (V_th) and optical transmission increases with increasing temperature. It may be due to the reduction in effective voltage drop across the liquid crystal droplets in the composite matrix. The liquid crystal droplet size was found to vary in the range of 5–28 μm.     

聚合物光限幅材料的研究

随着现代激光技术和武器的快速发展,急需激光防护材料(光限幅材料)和设备来防护人眼和光学传感设备免受激光的破坏.由于高分子光限幅材料具有大的非线性光学性能、快速的光学响应、高的损伤阈值和好的加工性能引起人们的广泛兴趣. 在这篇论文中,从分子结构以及分子结构对光限幅性能和光限幅机制的影响,对高分子光限幅材料进行了详细的综述,并提出高分子光限幅材料未来的发展方向.     

纳米羟基磷灰石/聚合物多孔复合支架材料

为提高骨组织工程支架材料的力学性能,改善其生物活性,综合天然与合成高分子的优点,采用溶液共混相分离法制备出聚己内酯(PCL)-壳聚糖(CS)多孔支架材料, 并进一步采用离心注浆法填充具有生物活性的纳米羟基磷灰石(HA)-聚乙烯醇(PVA)复合浆料, 制备了n-HA-PVA/PCL-CS复合多孔支架材料, 改善了PCL-CS支架材料力学性能。采用扫描电子显微镜、红外光谱、元素分析、孔隙率和抗压强度试验对材料进行了表征。结果表明, PCL-CS支架材料的内部具有蜂窝状的相互贯通的孔隙结构,孔隙率可以达到60%～80%。CS含量越大,孔隙率越大,而抗压强度越小。填充后的n-HA-PVA/PCL-CS复合多孔支架材料,孔隙率有所下降,但仍大于60%,而其弹性模量可提高至25.71 MPa。      

Flow-induced properties of nanotube-filled polymer materials

Carbon nanotubes (CNTs) are under intense investigation in materials science owing to their potential for modifying the electrical conductivity sigma, shear viscosity eta, and other transport properties of polymeric materials. These particles are hybrids of filler and nanoscale additives because their lengths are macroscopic whereas their cross-sectional dimensions are closer to molecular scales. The combination of extended shape, rigidity and deformability allows CNTs to be mechanically dispersed in polymer matrices in the form of disordered 'jammed' network structures. Our measurements on representative network-forming multiwall nanotube (MWNT) dispersions in polypropylene indicate that these materials exhibit extraordinary flow-induced property changes. Specifically, sigma and eta both decrease strongly with increasing shear rate, and these nanocomposites exhibit impressively large and negative normal stress differences, a rarely reported phenomenon in soft condensed matter. We illustrate the practical implications of these nonlinear transport properties by showing that MWNTs eliminate die swell in our nanocomposites, an effect crucial for their processing.     

Distinctive features of formation of the properties of certain polymer composite materials under the influence of wave action

Consideration has been given to the influence of vibrowave action on polymer dispersions (styrene-butadiene and acryl latexes and their blends), solutions of gelating polymers (polyacrylic acid, gelatin, and starch) with fillers (activated carbon and zeolite), and emulsions of the motor oil/water type. An increase in the degree of dispersity and the aggregative stability of disperse systems after their vibrowave treatment has been noted. An algorithm of calculation of a possible way of optimizing one method of intensification of mass transfer in the case where wave technology is used has been proposed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 5, pp. 170–175, September–October, 2005.     

Polymer matrix,polymer ribbon-reinforced transparent composite materials

Composites of a polymer–matrix reinforced by polymer ribbon monofilaments are investigated as mechanically robust, transparent composite materials. Transparent nylon monofilaments are mechanically worked to form flattened nylon ribbons, which are then combined with index-matched epoxy resin to create transparent composites. A range of optical and mechanical experiments are performed on composites and surrogate systems in order to quantify properties and guide system design. The results show that these polymer–polymer composites provide good transparency over a wide temperature range, and superior ballistic penetration resistance compared to monolithic transparent polymers.     

The physical properties of composite materials

In this review, the physical properties of composite materials are discussed; however, discussion of the mechanical properties has been excluded except when necessary for the consideration of properties such as thermal expansion or swelling and shrinkage. One of the main aims in the review has been to show how the theoretical and experimental information that is already available may be used (a) to design and construct composite materials with predetermined physical properties and (b) to ensure that the physical properties of composite materials are properly measured and properly defined.     

热固性聚合物基复合材料自修复技术研究进展

聚合物基复合材料修复技术的发展对于复合材料使用可靠性和使用寿命的提高具有积极的作用.根据热固性聚合物基复合材料自修技术最新研究情况,介绍了利用中空纤维、微胶囊、热塑性粒子、热修复等修复热固性聚合物基复合材料技术.     

Mechanical properties of glass polymer multilayer composite

The preliminary experimental studies on the comparative behaviour of the deformation processes involved in the failure of a commercial, 0.3 mm thick, 18 mm diameter soda-lime-silica glass disks (G) and multilayered glass disk-epoxy (GE) as well as glass disk-epoxy-E-glass fabric (GEF) composite structures are reported. The failure tests were conducted in a biaxial flexure at room temperature. The epoxy was a commercial resin and theE-glass fabric was also commercially obtained as a two-dimensional weave ofE-glass fibres to an area density of about 242 g m⁻². The multilayered structures were developed by alternate placement of the glass and reinforcing layers by a hand lay-up technique followed by lamination at an appropriate temperature and pressure. Depending on the number of layers the volume fraction of reinforcement could be varied from about 0.20 for the GE system to about 0.50 for the GEF system. It was observed that the specific failure load (load per unit thickness) was enhanced from a value of about 60 N/mm obtained for the glass to a maximum value of about 100 N/mm for the GE composites and to a maximum of about 70 N/mm for the GEF composite system. Similarly, the displacements at failure (δ) measured with a linear variable differential transformer (LVDT) were also found to be a strongly sensitive function of the type of reinforcement (GE or GEF) as well as the number of layers.     

The temperature dependence of the thermal constants of composite polymer materials

We developed a method for determination of the thermal-conductivity temperature dependence of organic and fiberglass plastics at temperatures up to 1000°C from thermocouple measurements by solving the inverse heat-conduction problem.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 6, pp. 1047–1051, December, 1977.     

Heat-treatment processes in the formation of components from polymer composite materials

A physicomathematical model of the heat treatment of components made from polymer composite materials on a rotating mandrel is considered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 813–818, May, 1988.     

Study on the properties of a nanocrystal and polymer composite PbTiO3/PEK-c film with optical anisotropy

Composite thin films of PbTiO₃ nanocrystals and PEK-c polymer for applications in nonlinear optical devices were prepared by spin coating. The size of PbTiO₃ nanocrystals was estimated to be 30–40 nm. The microstructure of PbTiO₃/PEK-c composite polymer film before and after poling was analyzed by X-ray diffraction, which show that this film is c axis-orientated. The poled composite film displayed the refractive index anisotropy. In this sample the TE- and TM-indices differences are found to be 0.02945 for 633 nm and 0.03915 for 414 nm. The electro-optic coefficient ₃₃ of poled composite film was measured to be 12.89 pm V^–1 at 633 nm by the transmission technique. The dielectric constant of it at 100 KHz under room temperature was determined to be 7.32. The figure of merit F ₂ was estimated to be 492. In addition, a relaxation process was observed in the time range of 28 days and the relaxation time constant was calculated to be 2393 min.     

Statistical analysis of the mechanical properties of composite materials

The Weibull statistic is currently used in designing mechanical components made of composite materials. This work presents useful formulae to describe the behaviour of the Weibull modulus estimator, which in turn may be described by means of a three-parameter Weibull distribution. Expressions for the parameters of this latter distribution, dependent on the sample size, are also given in the paper, so, the percentage points, published until now in tabular form, may be directly calculated. Empirical expressions are derived for determining the A-basis and the B-basis material properties as a function of the sample size.     

Electromagnetic properties of phosphate-coated ferrite composite materials

Sintered ferrite was treated with phosphoric acids to form phosphate-coated powders. The formation of the coating layer was verified by the improvement of oxidation resistance, microscopic morphologies, and evident reduction of conductivity of the powders. The coated powders were then blended with silicone to fabricate composite materials. The electromagnetic properties of the composites at the frequency range of 1?MHz to 1?GHz were investigated and found to be noticeably affected by the surface condition of the powders. The coating layer significantly reduced the imaginary part of permittivity of the composite owing to the improvement of insulation, while the resonance frequency was scarcely affected. The magnetization curves revealed that, compared to the composite containing as-prepared powder, the coated powder filled composites exhibited enhanced demagnetizing field, which consequently contributed to an obvious depression in magnetic permeability. Due to the modification of electromagnetic properties, the phosphate-coated ferrite composites were found to be practical materials as a substrate of radio frequency identification (RFID) metal tag. The impedance measurement results revealed that the phosphate-coated ferrite composites could remedy destructive interference imposed by metal and was beneficial for fabrication of RFID metal tag.     

Preparation and properties of close-packed composite materials

Monodisperse silica particles of about 0.3m diameter are suspended in methacrylate monomer using a carefully selected dispersant. Many steric dispersants are hydrocarbon chains with a reactive end-group. These are not effective as dispersants for silica in moderately polar solvents, such as esters and the methacrylate monomers. Good dispersion was obtained with a methacrylate polymer terminated by a chlorosilane end group. Settling or centrifugation of these unagglomerated dispersions gives well-packed particle beds. Polymerization of the surrounding monomer produces composite materials with high packing fractions and a high degree of regularity. Moduli and strengths of these composites are reported.