Aspects of the applications of composite materials in combustion engines

The paper presents the results of investigations concerning the possibilities of application of composite materials in the construction of internal combustion engines. The total mass of the engine can be reduced by allying composite materials, which have a much higher strength than hitherto applied conventional materials. Less thermal expansion allows reducing assembly clearance between the piston and cylinder. The surface topography after the process of machining of composite materials contains hollows, which act as trays for lubricant, wear products and pollution particulates. Therefore, it is possible to reduce friction, fuel consumption, level of exhaust emission and improve the durability of engine. During the investigations, the engine piston made of aluminium matrix composite has been tested. The tests were related to the influence of surface topography of the piston skirt containing Al2O3 particles on the adsorption of lubricating oil, which facilitates lubrication in small displacement test engine. Aluminium matrix composite materials have some disadvantages, too. The most important are higher finishing costs and higher wear of the other sliding element. To reduce the finishing costs of making the suitable surface, special methods for example water jet cutting, have been worked out. To reduce the wear of the other sliding element, reinforcing spherical particles without sharp edges should be applied. Covering the tribological partner-sliding surface with a composite surface layer (e.g. Cr+Al2O3) can result in a relevant reduction of its wear.