Transient Thermal Deformations of the Interphase in Polymer Composites

Heterodyne micro-interferometry was utilized to measure out-of-plane transient displacements in the interphase due to thermal cycling. In-situ measurements were made on single carbon fiber/epoxy samples with interphases of varying glass transition temperature. Interphase properties were tailored such that one set of samples had fibers which were coated with a low T_g resin, another set had a higher T_g coating, and in the third set the fibers were uncoated. The interferometric data demonstrated that interphase T_g has a significant effect on the rate and magnitude of the thermal deformations at the fiber/matrix interface. The presence of a low T_g interphase caused an increase in the magnitude of the thermal displacements due to a local softening of the matrix and increase in coefficient of thermal expansion. In addition, the rate at which the displacements increase was also higher due to the reduction in T_g. Samples with untreated fibers (no tailored interphase) behaved as if a low T_g interphase had formed. Experimental displacement profiles were also compared with finite element predictions to assess the behavior of the tailored interphases.     

Influence of Matrix Properties on Fragmentation Test

Physical aging was used to vary the mechanical properties of model single fiber composites without changing the chemistry at the interface in order to study how property changes affect the measurement of interfacial adhesion by the fragmentation test. The properties of epoxy matrix/AS4 single fiber composites driven to full cure (T_g = 166°C) are altered by annealing below T_g. Neat resin samples with identical thermal histories are tested. All aged panels show roughly the same embrittlement with aging characterized by an average 30% decrease in tensile failure strain and 7.3% increase in compressive yield relative to quenched samples. Fragmentation results indicated no change between aged and quenched samples. Results are discussed in terms of micromechanics models for the fragmentation test. Strain at fragmentation increased with aging. This was related to the residual stress state in the model composite and the possibility of the zero stress state of the single fiber composites increasing with thermal annealing.     

含负折射率介质的一维光子晶体的带隙结构

提出了用正、负折射率介质层交替排列构成的一维光子晶体模型,并且用传输矩阵法计算了该模型的透射谱,从理论上分析了其带隙结构。发现负折射率介质层的引入导致了奇异的带隙特性:禁带很宽,禁带宽度2△ε／ε0趋于2,导带为没有振荡的尖锐峰;禁带宽度对折射率对比度和周期数的变化非常敏感。     

分形和空间灰度共生矩阵联合评价断口形貌研究

为了全面描述断口形貌特征，采用分形和空间灰度共生矩阵结合的方法，对4个典型断口形貌进行定量分析．结果表明：分形维数与断口的粗糙度和复杂度相关；灰度共生矩阵的每一个二阶统计参数都可以精确地描述断口形貌的某一特征，具有较好的纹理表达能力；将灰度共生矩阵的二阶统计参数和分形维数相结合组成多维特征集可以较完整地描述断口图像的纹理特征．分形和空间灰度共生矩阵的联合评价方法，可望实现断口类型的自动分类识别，同时对处理其它纹理图像具有一定的借鉴作用．     

优势关系下的相容约简和下近似约简

定义了决策表在优势关系下的相容约简和下近似约简,优势关系下的相容约简是优势关系下一致决策表约简的推广。证明了优势关系下的下近似协调集是优势关系下的相容协调集。举例说明了优势关系下的相容协调集不是优势关系下的下近似协调集,给出了优势关系下的相容约简和下近似约简的判定定理和可辨识矩阵,由此可以给出它们的约简算法。     

不确定性关联时滞大系统的分散鲁棒镇定

应用线性矩阵不等式（LMI）方法研究不确定性关联时滞大系统的分散鲁棒镇定问题。系统中不确定项具有数值界，可不满足匹配条件。基于不确定项的表达形式，给出了其可分散状态反馈镇定的充分条件，即一组LMIs有解。在此基础上，通过求解一凸优化问题，给出了具有较小反馈增益的分散稳定化状态反馈控制律的设计方法。仿真示例说明了该方法的有效性和优越性。     

一类分块Hankel矩阵及其可逆性

由线性系统的可控性矩阵得到一类分块Hankel矩阵，通过可控性分析讨论了它们的若干性质，得到了这一类分块Hankel矩阵的可逆条件，特别地可以得到卜循环分块矩阵和一般数值Hankel矩阵的相应性质，为这一类分块矩阵及其相关矩阵的研究提供了一种新的方法。     

Quantum analysis of measurement results

It is shown that a stochastic matrix operator (quantum measurement matrix) may be considered in some cases as a density matrix. Results of measurements in the form of figure numbers, interconnected with a matrix of quantum measurements, are similar to quantum observable quantities determined in quantum statistical theory. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 3–8, December, 2006.     

Micro- and nano-scale deformation behavior of nylon 66-based binary and ternary nanocomposites

The primary aim of this paper is to provide an insight on the effect of the location of organoclay on the micro- and nano-scale deformation processes in melt-compounded nylon 66/organoclay/SEBS-g-MA ternary nanocomposites prepared by different blending sequences. In addition, the deformation processes of the ternary nanocomposites were compared to the binary nanocomposites (nylon 66/organoclay and nylon 66/SEBS-g-MA) and neat nylon 66. The incorporation of SEBS-g-MA particles toughened nylon 66 markedly; but the flexural modulus and strength were both reduced. Conversely, the use of organoclay increased the modulus but decreased the fracture toughness of nylon 66. Nylon 66/SEBS-g-MA/organoclay ternary nanocomposites exhibited balanced elastic stiffness and toughness. Stress-whitening studies of the fracture surfaces in terms of gray level were also performed and an attempt was made to correlate the optical reflectivity characteristics with fracture toughness. It was concluded that the capability of SEBS-g-MA particles to cavitate was decreased by the presence of organoclay in the SEBS-g-MA phase, resulting in reduced toughening efficiency. The best micro-structure for toughness and other mechanical properties is thus to maximize the amount of exfoliated organoclay in the nylon 66 matrix rather than to have it embedded in the finely dispersed SEBS-g-MA particles.     

Machinability of Metal Matrix Composites Reinforced by 3-D Network Structure

Metal matrix composites reinforced by three-dimensional (3-D) continuous network structure reinforcement (3DCNRMMC) are difficult to machine due to serious tool wear and poor surface roughness caused by the brittle and hard reinforcement which interpenetrate into ductile matrix. In order to achieve the approach of low cost of 3DCNRMMC, the machinability of it needs to be understood. The influences of three cutting parameters and volume fraction of reinforcement on cutting force were analyzed in detail. The results indicate that: (1) Due to the brittle phase(s) introduced into ductile matrix of composites, there is a large fluctuation of cutting force causing deterioration of machinability. The fluctuation ranges of cutting forces, initially increase rapidly with the increase of volume fraction of reinforcement and then decrease finally, are largest at the range of the volume fraction of 55–65%; (2) The influence of cutting parameters on cutting force is obvious. With the increases of cutting speed, cutting force decreases gradually unless cutting speed exceeds the value of 209 m/min. Cutting forces increase with increasing feed rate and depth of cut; (3) Owing to the large fluctuation of cutting force, there were some cratered surfaces caused by Si₃N₄ reinforcement pulling-out and flaking-off. Some brittle phase protruding from the machined surface caused the deterioration of machined surface.