The article verifies some approximating power-law and hyperbolic dependences between stresses σ and deformations ε for experimental deformation diagrams of cement concrete and polymer concrete. When analyzing the state and residual life of reinforced concrete structures, one has to solve the problem of determining the relationship between stresses and deformations in various design sections of structures. The traditional approach, based on the selection of the approximating function "σ – ε" from the numerical values of the deformation diagram obtained by testing samples (cubes, prisms, cylinders), is practically impossible. Therefore, an alternative approach is proposed based on the selection of an approximating function according to standardized indicators: ultimate strength (σ_bu); modulus of elasticity (E_b0); ultimate deformation (ε_bu). The numerical values of the normalized indicators can be determined at a given point by analyzing the results of indentation of the indenter into the material of structures. As approximating ones, consider the power functions that are most preferable for materials with a fractal structure. Various boundary conditions are considered for determining the constant coefficients α and β according to the system of normalized indicators. The graphs of changes in tangent modules are analyzed.
A new approach to the creation of composite materials using system analysis methods is proposed. A composite is considered as a set of elements connected by relations generating an integrative quality. When studying the properties of materials, synergetic, informational and homeostatic approaches are implemented. It is noted that when the integrative parameters of the system approach the maximum permissible, a systemic crisis occurs: the system enters the bifurcation zone. The system attributes and methods for selecting elements and subsystems are determined taking into account the paradoxes of integrity and hierarchy; their implementation is indicated in the development of radiation-protective composite materials. Issues of paradigm shift in the development of composite materials are touched upon. The new paradigm does not include the old one. It is stressed that in a paradigm shift there is no continuity of theories; Involves the formation of another system of views based on fundamentally new basic models and the change of the principle of management of initial structure formation. On identification, the principle of simulating a complex system is used (it was represented by a finite set of models that reflect a certain facet of its essence) and purposefulness (matching a complex system with many private criteria and specially developed global criteria that describe its existence as a whole). An example of the synthesis of composites based on the identification of kinetic processes of formation of their physical and mechanical characteristics is indicated. Some aspects of evaluating the durability of materials are considered; the destruction of the system is interpreted as a catastrophe associated with a violation of homeostasis. It is assumed that structural elements are formed from elementary particles, which, under the influence of external factors, are combined into molecules, clusters, globules and fibrils; associative clusters and more complex ordered packing of structural elements appear. The approaches of Benoit Mandelbrot are used, a quantum-mechanical description of the process of destruction of a solid body: a solid body is represented as a set of elementary oscillators; energy is released and absorbed by elementary portions - quanta; destruction of one structural element does not lead to destruction of the entire system; destruction is considered as a process proceeding at scale levels. An illustration is given of a systematic approach to modeling a cement composite as a complex scale-invariant system with the indication of particular models.
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