Application of fractal theory to the study of adhesive bonding

Fractals are found in the structure of solids, self-similarity is also characteristic of the structure of wood. The property of individual parts to be similar to the entire structure as a whole is called fractal. Based on the application of the principles of fractal geometry, the equations of topochemical kinetics are modified. This approach makes it possible to generalize the existing equations and obtain more accurate values of the kinetic parameters. Being a quantitative integral characteristic of the microstructure of an object, the fractal dimension makes it possible to find its surface area or volume with a given level of approximation. At the same time, the relationship between the surface area of solid-phase reagents and their fractal dimension makes it possible to use it in a formal kinetic analysis. To describe the kinetics of processes involving reaction centers, the «reaction fractal dimension» can be used, i.e. the dimension of the set of reaction centers. The introduction of fractal dimension into the equations of topochemical kinetics makes it possible to quantitatively take into account the influence of the state of the surface, as well as, in the future, the change in its morphology with time. Understanding the principles of constructing fractal systems, it is possible to determine the structure and topography of the surface of porous bodies, in particular, the glue joint of wood (plywood), which was the goal of this work. Based on the measurements carried out, we came to the conclusion about the heterogeneity of the structure of wood, in the framework of the theory of fractals. The main factor indicating the heterogeneity of the wood structure is the consolidation processes in one form or another, present in the plywood production technology. It is assumed that the composite wood material, in particular plywood, has a dispersion base, i.e. the skeleton of the material is formed by dispersed particles (a wood substance partially filled with glue) and interparticle pores. The idealization of wood-polymer material is carried out, since by their nature such materials are consolidated dispersed media, in their manufacture it is necessary to take into account random deviations and random interactions of technological factors. To build the structure of a wood-polymer material (plywood), a method for determining the fractal dimension is used, based on measuring the laws of density distribution in composites. The fractal dimension can be used as a universal constant characterizing the structure of the composite. The values of the fractal dimension obtained by us for plywood based on modified adhesives indicate that the so-called superposition (overlay) of both types of components (resin and modifier) takes place during manufacture. Note that the fractal dimension is sensitive to changes in technological regimes, so when the nature and nature of the modifier change, the fractal dimension changes, as well as, in our opinion, the physical and mechanical parameters of plywood.

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