In this paper the results of mechanical studies of the Aropol 536 composite on the epoxy-resin base are described. The aim of the studies was to measure elastic-plastic changes in the composite during its deformation. The obtained results were analyzed using Kolmogorov-Sinai metric entropy. The entropy was computed applying phase portraits reconstructed from a phase plane using delayed coordinates. Resolution of the particular experimental setup limits the number of the acquired data points, i.e., from several to tens of thousands of points and it has significant influence on accuracy of the obtained results. In conclusion, in the tested composites elastic-plastic deformations are periodic and repeat in a distinctive way in a wide range of deformations of the sample. Deformation of the elastic-plastic composite are associated with its complex structure and studies of its mechanical properties require more advanced methods such as use of Kolmogorov-Sinai metric entropy.

The yield point is one of the basic characteristics of construction materials, which are used in the design engineering calculations. The methods used to determine the yield point is based on the interpretation of the geometric shape of the curve uniaxial tension. This shape is specific for different construction materials and depends among others to the conditions carrying trials. Specific guidelines for determining the yield point were included in the standards specification. The conventionality of procedure concerns especially materials, which, in their deformation characteristic do not have a distinct top of knee. The authors propose an alternative method based on the use of the concept of the metric entropy by Kolmogorov-Sinai. The metric entropy by Kolmogorov-Sinai is used to study the phenomena about a dynamic character. Therefore, this method requires the recording of more number of measuring points: from a few hundred to a dozen thousand, depending on the type of research of constructional materials. A dynamic character of measurement data results from their scatter, which consists of local, non-linear disturbances occurring during deformation of the material and the noise, associated from the action of acquisition path. The aim of the study is to present a more objective method of determining the yield point structural materials, which do not require the use of conventional procedures. The paper presents the results determining of this constant material on the basis of data records monoaxially stretching of tests for metals used in shipbuilding.

ObstractComposite materials have nowadays become a group of construction materials whose application in mechanical structure designing has been constantly increasing. There is therefore a real demand for an objective opinion on the mechanical properties of composites. According to the authors, determining those properties based on the recommended methods included in current standards requires objectivization. The difficulty is that those methods are usually based on the geometrical shape of stress curves in the strain function. The study proposes an new method of testing the mechanical properties of composites through analyzing the internal dynamics of measurement data based on uniaxial stretching tests. A tool in such an analysis is determining the Kolmogorov-Sinai metric entropy values of measurement data. Nine samples of composite materials having various compositions have been tested. In selecting these materials, the focus has been on the possibility of introducing composite recyclates as their structural components.