Przedstawiono szeroką analizę czynników strukturalnych warunkujących często pojawiające się niezgodności wyników eksperymentalnych z modelami teoretycznymi, opisującymi własności kompozytów metalowych umacnianych cząstkami ceramicznymi. Do opisu matematycznego własności mechanicznych tego typu materiałów kompozytowych zaproponowano zaadaptowanie funkcji Maxwella, poszerzonej o parametr wprowadzony przez Halpina i Tsaia. Model ten znalazł bardzo dobre potwierdzenie w wynikach badań eksperymentalnych wytrzymałości na rozciąganie oraz umownej granicy plastyczności określonej dla kompozytów MgAI5-SiC.
While considering metal composites reinforced with ceramic particles, which are frequently obtained by casting, one cannot apply models developed for fibre composites to search for correlations, especially the ones involving mechanical pro perties. The relationships derived on basis of the additivity laws are not valid here, either for the assumption of constant stress or constant strain. Basic factors modelling the structure and properties of such composites, which should be selected while designing the specified material, are presented in Fig. 1. In the case of cast composites the greatest concern is given to the obtaining of the proper volume fraction of the particles within the matrix volume, the fraction being frequently corrected according to the actual one. Then the constant level of other factors is assumed for considering the composite. This leads to the neglecting of many dependent variables, the following being counted to them: - changes of chemical composition of the matrix caused by introduced particles or other additions (Fig. 2), - differences in the character of the joint between components, which greatly affect the obtained level of mechanical properties (Fig. 3), - uniformity (or the lack of it) of arrangement of the particles in the matrix, - changes in the matrix grain size due to introducing various volume fractions of ceramic particles of different size, - various degree of porosity (Fig. 4). Due to the presented numerous factors determining the structure of the cast metal composites reinforced with ceramic particles, reasons of frequently occurring inadequation of numerical models and experimental data seems to be obvious. After a series of analyses and experiments on composites reinforced with particles it seems that the most adequate model would be the one adopting Maxwell's relationship between a parameter (a property) and the volume fraction, properties of components, and their interaction. This function shown in a general form by Eq. (1) has found rather strict confirmation in the results of experiments performed for Mg/SiC composites. Fig. 5 presents experimental data as compared with theoretical values obtained from Eq. (1) for tensile strength and yield strength versus SiC volume fraction.