Thermoelastoplastic deformation of complexly reinforced shells

The problem on the elastoplastic deformation of reinforced shells of variable thickness under thermal and force loadings is formulated. A qualitative analysis of the problem is carried out and its linearization is indicated. Calculations of isotropic and metal composite cylindrical shells have shown that the load-carrying capacity of shell structures under elastoplastic deformations is several times (sometimes by an order of magnitude) higher than under purely elastic ones; the heating of shells with certain patterns of reinforcement sharply reduces their resistance to elastic deformations, but only slightly affects their resistance to elastoplastic ones; not always does the reinforcement in the directions of principal stresses and strains provide the greatest load-carrying capacity of a shell; there are reinforcement schemes that ensure practically the same resistance of shells at different types of their fastening. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 707–728, November–December, 2006.     

Controlling the thermomechanical properties of polymer nanocomposites by tailoring the polymer–particle interface

We show that the thermomechanical properties of polymer nanocomposites are critically affected by polymer-particle wetting behavior. Silica nanoparticles grafted with dense polystyrene brushes of degree of polymerization 1050 are blended with polystyrene melts to form nanocomposites. It was found that low molecular weight (MW) polystyrene melts with lengths <880 wet these particles. Concurrently, the glass transition temperature (T_g) of the nanocomposite increases. At higher MW, the matrix does not wet the particles and the T_g decreases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2944–2950, 2006     

Inverse Problems of the Mechanics of Thin-Walled Composite Structures

New formulations and methods for the solution of the inverse problems of thin-walled layered and reinforced shells and plates are discussed. Rational projects with regard for the requirements of nonflexural deformations in layered structural members, the given deformability of particular surfaces, the realization of a strictly momentless state, an equally stressed reinforcement, and the breaking strength of the binder at the interfaces are investigated. A brief review of the known solutions to these problems is given, and solutions to some new problems are described.     

Nanocellulose reinforced as green agent in polymer matrix composites applications

Owing to their abundance, high strength and stiffness, and low weight and biodegradability, nanocellulose (NC) is regarded as a promising candidate for the preparation of green composites. The high reinforcing effect assigned to the mechanical percolation phenomenon of NC is due to the stiff continuous networks of cellulosic nanoparticles linked via hydrogen bonding. Compared to nanocrystalline cellulose, NC fibers result in more significant improvement to the modulus, stiffness, and strength as aspect ratio NC fiber is higher compared to NC crystal. Indeed, in the case of biopolymer composites, the reinforcement effect of NC is attributed to the NC‐polymer interactions and the reinforcing effect occurring through effective stress transfer at the NC‐polymer interface. The NC‐reinforced composites tend to become more brittle as the concentration of the reinforcing particles increase up to the saturated level, due to the reduction in surface adhesion between filler and matrix. Due to its promising mechanical and structural stability, NC composites have been used widely in many industrial applications such as food packaging, electronic applications, and tissue engineering.     

Rational Profiling of Reinforced Rotating Disks

The problem of rational profiling of thermoelastic three-layered reinforced rotating disks of gas turbines is formulated. The conditions of equal-stressed reinforcement of the midlayer and the condition of equal-strength binder of the reinforced layer or external isotropic layers are used as criteria for rational designing. An iterative method is proposed for solving such problems. The problem of rational profiling of disks with radial and radially circumferential reinforcements, on condition that the fibers of the radial family are equally stressed, is solved analytically. The calculation results for B-Al and B-Ti disks, obtained by using both the criteria of rational design, are given for plane-parallel and 3D reinforcements. It is shown that, at an equal load-carrying capacity, the weight of such disks can be 30-60% smaller than that of reinforced disks of constant thickness, or, at an equal weight, they can have a considerably higher load-carrying capacity. The criterion of equal-stressed reinforcement, as a rule, is more efficient than the condition of equal-strength binder.     

Experimental Evaluation of the Effect of the Structure of Composite Rings on Their Properties in the Radial Direction

Based on the results of bending tests on cut glass-fiber-reinforced plastic rings with a longitudinal-circumferential reinforcement, their radial peel strength is evaluated. The effect of the fiber layout on the properties of the rings in the radial direction is investigated. It is shown that their radial tensile strength only slightly depends on the fiber layout but is basically determined by the properties of the polymer interlayer between the fibers. In radial tension, the presence of fibers in the polymer layer leads to a strain concentration, which results in a premature failure of the polymer phase of the composite. The strain-concentration factor cannot be used for an accurate prediction of the breaking stresses or strains of the composite, because of different failure modes of the pure resin and the composite.     

脉冲磁体增强技术发展概述

在脉冲强磁体设计中，磁应力是目前面临的最大困难，当磁场强度达到100T时，磁体绕组中的磁应力高达4GPa，这是目前任何实用导体材料都无法随的，因此，脉冲强磁体的发展在很大程度上取决于磁应力的解决情况，文章介绍了国外在解决脉冲强磁体巨大问题上采用的方法，主要叙述了新材料技术，绕组加固技术和改善电流分布技术，并对其优缺点及性能进行了分析。     

A 4D Composite Reinforced along Cube Diagonals with a Small Content of Yarns under Large Shear Deformations

The deformation behavior of a 4D composite reinforced along cube diagonals under large shear deformations is examined. The investigation is based on an applied theory which allows one to perform a macromechanical analysis of composite materials with small volume contents of reinforcing yarns to an accuracy sufficient in practice. Qualitative differences between the properties of such composites under large and small shear deformations are revealed. The evolution of the structural geometry of the deformed composite material is traced.     

Modelling and hierarchical learning control of a dryer

This paper deals with modelling and hierarchical learning control of an industrial phosphate dryer. The model is derived from heat and mass balances. It consists of hyperbolic nonlinear partial differential equations. The control and the output variables appear at the boundary conditions. The method of characteristics that is based on two independent variables is used for numerical simulation purposes. The control objectives are to minimize fuel consumption and to keep the moisture content of dried phosphate close to a desired value, despite external perturbations acting on the drying process. The fuel flow and the dried product moisture content have been selected as control variables. A hierarchical learning system, operating in a random environment that corresponds to the dryer, is used for control purposes. During its operation the learning system collects the pertinent information about the variables that describe the process to be controlled and generates a control action. The obtained results show the good performance characteristics of the considered controller.     

Electrical and mechanical behavior of filled elastomers. I. The effect of strain

Electrical and mechanical property tests have been used to examine the changes in the carbon black network structure that occur in a filled elastomer at large strains in tension and compression. These changes have been examined both in materials that have no previous loading history and in test pieces that have been subjected to a specific known prestrain. When a previously unstrained, filled elastomer specimen is stretched to moderate extensions, the electrical resistivity increases. This is ascribed to the breakdown of the carbon black network structure. At higher tensile extensions, the resistivity decreases. This reduction in the electrical resistivity is attributed to the alignment of the shaped carbon black aggregates under strain. During unloading, the resistivity behavior is different from that during loading, with the final unloaded electrical resistivity being significantly higher than that measured in the unstrained elastomer. This dramatic change in the electrical properties after unloading is in marked contrast to the relatively modest changes observed in the mechanical behavior. After the first cycle, the electrical behavior becomes much more reversible, and this indicates that the bulk of the damage experienced by the carbon black network is developed during the first cycle. After unloading from a large strain, the electrical anisotropy is small, whereas the mechanical anisotropy is more marked. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2079–2089, 2003