Spatial and polarization characteristics of radiation reflected by composite materials

In the spectral regions 0.63 and 1.15 m, measurements are made of the degree of polarization and indicatrix of radiation reflected from the surface of composite materials before and after their heating in air by radiation from a CO₂ laser.Notation wavelength at which measurements are made - p() spectral reflection coefficient - equivalent solid angle - d elementary solid angle - total reflected radiant flux - I₀ intensity of radiation in the direction of mirror reflection - f() normalized indicatrix of the reflected radiation - angle at which the degree of polarization and the intensity of the reflected radiation were measured - P degree of polarization of the reflected radiation Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 5, pp. 753–759, May, 1989.     

Intensity and phase of reflected radiation in a vanadium dioxide structure with surface plasmons

Results of theoretical calculations are presented for the angular dependences of the reflection coefficient and phase of reflected p-polarized radiation at wavelengths of 6328 Å and 11 500 Å in vanadium dioxide layered structures with surface plasmons. Results of calculations are presented for the two phases of the vanadium dioxide films — semiconducting and metallic. Pis’ma Zh. Tekh. Fiz. 23, 32–36 (July 12, 1997)     

Influence of the polarization azimuth of incident radiation on space-polarization characteristics of the flux reflected by composite materials

At the wavelength 0.63 m the degree of polarization, the angle of rotation of the polarization plane, and the indicatrix of the intensity of radiation reflected by the surface of composite materials before and after their heating by radiation of a CO₂ laser were measured.B. I. Stepanov Institute of Physics, Belarussian Academy of Sciences, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 4, pp. 442–447, April, 1994.     

Fractal characteristics of the deformation surfaces of a composite material and their correlation with the structure

An investigation was made of the deformation relief formed at the surface of a solid under active deformation, and its fractal properties were determined. A correlation was established between the fractal dimension of the surface profile and the parameters of the fine crystalline structure of the material. Pis’ma Zh. Tekh. Fiz. 25, 34–38 (January 26, 1999)     

Vibrational analysis of a double-layer composite material structure

As new manufacturing techniques for glass reinforced polymers are developed and existing ones improved, new structural engineering design methods will become available for the construction industry to exploit. The most promising area currently is the pultruded double-layer skeletal fibre/matrix structural system. Considerable research effort has been directed towards design techniques and structural imperfections associated with those systems under static loading. This paper discusses the analysis of a particular type of double-layer skeletal structure, under dynamic loading and manufactured by the pultrusion method. Analytical and experimental techniques have been used in the analysis, and a discussion of these techniques is presented. It is concluded that, provided great care is taken in modelling the analytical system, good agreement between the two methods of analysis is obtained; it is necessary that mechanical properties of the material of the prototype are accurately determined.     

Evolution of the diffraction pattern of probing radiation reflected by a silver surface upon melting

Evolution of the diffraction pattern was studied experimentally using a sample of silver with a moderately rough surface formed by the composition of predominantly unidirectional grooves. The sample was heated in a tubular electric furnace; its temperature was determined by a thermocouple measurement. At a temperature close to the liquidus temperature, the appearance of isotropically scattered radiation, concentrated near the specular beam, is detected. We analyzed the evolution of these radiation components upon melting and showed that the nucleation is the source of isotropic scattering. It is found that the evolution of the diffraction pattern enables one to observe the melting of the surface layer, accompanied by the simultaneous existence of the disappearing solid phase and the growing liquid phase. Spreading of the sample melt over a substrate can be also observed with the diffraction pattern.     

Super-high-frequency heating of a composite material of a periodic structure

Summary.  In this work there is given the solution of a problem of a laminated composite and of a fibrous one-way directed composite with regular arrangement of fibres. Such structures are the simplest technologic ones and are taken as model objects. In the process of solution there were used the known mathematical methods of heat conductance and electromagnetism [5], [6]. Derivation of Maxwell's averaged equations and the general variated formulation of the problem on a cell for a composite insulator and conductor are given in [7]. Averaging of Maxwell's equations for monochromatic electromagnetic fields is considered in [8]. The general scheme of the solution of the problem of heating of a composite material of periodical structure in a high-frequency electromagnetic field is considered in [9]. (Received June 11, 2001; revised mai 27, 2002)     

Study of the heat-transfer characteristics of a thermally protective composite material

Results are presented from a theoretical-experimental study of the thermal conductivity of a thermally protective composite for different models of heat transfer.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 6, pp. 989–994, December, 1985.     

CO2 laser radiation confinement in a composite material containing silver nanoparticles

Experimental data are reported on the optical confinement of a pulsed 10.6 μm laser radiation in a composite comprising a dielectric medium with linear optical properties containing dispersed silver nanoparticles. The energy threshold for the laser radiation confinement at a pulse duration of 2 μs does not exceed 10μ J/cm²     

Effect of a machining-induced defect on the tensile strength of a 3D composite material

This paper investigates the effect of finite specimen size upon the tensile failure of a tridirectional carbon-carbon composite along each reinforcement axis. Asymmetry in the position of load-bearing axial yarns across the cross-section is generated randomly by machining. This yields parasitic bending of the specimen, and thereby premature failure of the yarns subjected to the maximum bending stress. However, bending effects become negligible at final failure. Additionally, the composite failure strength _F is determined from the cross-sectional area of the actually load-bearing axial yarns, using both symmetrical and asymmetrical specimens. Results are in good agreement with previous work, and we show that the variability of _F is small.     

Calculation of the statistical characteristics of the light reflected by a rough random cylindrical homogeneous Gaussian surface

Statistical characteristics of light reflected by a rough random cylindrical homogeneous Gaussian surface are investigated using a modified method of specular points, as developed by Gardashov. In this proposed method, a special procedure for determining the light intensity near the caustics has been formulated. The probability distribution of the intensity of reflected light is expressed in terms of a special function, which is determined by the characteristic function of distribution of radii of curvature at the specular points and the distribution density of the number of specular points. The distribution of radii of curvature, derived by Gardashov, and expressed in terms of dimensionless radii of curvature, has a simple expression which does not contain any parameter of the surface (as a surface rms deviation, etc.). Consequently, it is universally valid and applicable to any cylindrical homogeneous Gaussian surface. After modification, the infinite dispersion of the reflected light intensity turns into a finite. The relationship between the distributions of reflected light intensity and the number of specular points, in the form of a Fredholm integral equation of the first kind is obtained. The kernel of the integral equation is expressed in terms of a characteristic function of the radii of curvature at specular points. The validity of formulae and relationships, thus derived, is tested by numerical simulations.     

Screening of a surface by reflected particles

A model is proposed for the process of screening of a surface by expelled and reflected particles in a dust flow together with a method for evaluating the screening effect in the vicinity of the body's critical point.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 3, pp. 428–435, September, 1986.     

Self-defocusing of laser radiation in a composite material containing ZnSe:O nanoparticles

We present experimental data on the self-defocusing of nanosecond pulses of 0.53-, 1.06-, and 1.54-μm laser radiation in a thick composite material containing nanoparticles of oxygen-doped zinc selenide. This medium can provide for a linear transmission coefficient of 50–60% at a 20–50 pJ energy threshold for the onset of a nonlinear optical response.     

Temperature dependence of the intensity and phase of reflected light in a liquid-crystal structure with surface plasmons

The results of a theoretical calculation of the temperature dependence of the amplitude coefficient and phase of reflected radiation with wavelength λ=6328 Å in a liquid-crystal structure with surface plasmons are reported for the first time. The computational results could be helpful for developing temperature sensors and optically coupled thermal imagers based on liquid-crystal structures with surface plasmons. Pis’ma Zh. Tekh. Fiz. 23, 11–15 (September 12, 1997)     

金属橡胶材料双层结构吸声特性研究

理论研究了金属橡胶材料双层结构吸声特性。根据金属橡胶材料声学特性参数计算式,推导出两种基本双层吸声结构—置于刚性墙和带有空气层吸声结构的声阻抗率和吸声系数计算式。确定了流阻率是决定金属橡胶材料声学特性的基本参数。分析了各层材料厚度、流阻率及空气层厚度对两种吸声结构吸声性能的影响关系,对比分析了双层吸声结构与单层吸声结构的吸声性能。研究结果表明:通过合理设计双层吸声结构,可使其在很宽的频率范围内具有良好的吸声性能。     

氧化剂对聚吡咯复合材料介电性能的影响

为了探究氧化剂对聚吡咯复合材料介电性能的影响,以吡咯为单体,采用原位聚合法制备了聚吡咯涂层复合材料。通过BDS50介电谱仪研究了氧化剂种类和氧化剂物质的量浓度对复合材料介电常数实部、虚部、损耗角正切、表面电阻的影响;采用Quanta200型环境扫描电子显微镜和Instron万能材料试验机研究了聚吡咯涂层复合材料的外观形貌和强度。结果表明:氧化剂种类、氧化剂浓度对聚吡咯涂层复合材料介电常数实部、虚部、损耗角正切、表面电阻影响较大;制备的聚吡咯涂层复合材料既具备良好的介电性能和导电性,又兼具良好的强度.     

Effect of a change in phase of the reflected wave on measurements of the shape of a surface in optical profilometry

We examine the effect of a change in phase of the reflected electromagnetic wave when measuring a surface profile using a scanning white-light interference microscope and a phase-shifting coherent light interference microscope. We present the results of experiments measuring the thickness of an aluminum coating deposited on a silicon wafer, without any phase shift correction and with phase shift correction, calculated from handbook data and from the results of ellipsometric measurements. We compare with the results of measurements on the same object on an atomic force microscope.     

Voltage dependences of the amplitude and phase of reflected radiation in liquid-crystal structures with surface plasmons

The results of a theoretical calculation of the amplitude and phase of p-polarized monochromatic radiation reflected from layered liquid-crystal structures with surface plasmons as a function of the external voltage applied to the structure (in the Kretschmann geometry) are reported. Pis’ma Zh. Tekh. Fiz. 23, 75–80 (September 26, 1997)     

Effect of the expansion velocity of material of a sand protective screen on the attenuation of a shock wave reflected from this screen

The effect of a sand protective screen on attenuation of the shock wave reflected from the screen has been studied experimentally and numerically. The measurements are compared with the data on the effect of the screen thickness on the attenuation of the reflected wave.     

Topology optimization of composite material plate with respect to sound radiation

In this paper, topology optimization of composite material plate with respect to minimization of the sound power radiation has been studied. A new low noise design method based on topology optimization is proposed, which provides great guidance for acoustic designers. The structural vibrations are excited by external harmonic mechanical load with prescribed frequency and amplitude. The sound power is calculated using boundary element method. An extended solid isotropic material with penalization (SIMP) model is introduced for acoustic design sensitivity analysis in topology optimization, where the same penalization is applied for the stiffness and mass of the structural volume elements. Volumetric densities of stiffer material are chosen as design variables. Finally, taking a simple supported thin plate as a simulation example, the sound power radiation from structures subjected to forced vibration can be considerably reduced, leading to a reduction of 20 dB. It is shown that the optimal topology is easy to manufacture at low frequency, while as the loading frequency increases, the optimal topology shows a more and more complicated periodicity which makes it difficult to manufacture.