On the question of the accuracy of determining the mechanical characteristics of carbon-carbon composites from samples obtained by hydro-cutting

Abstract

The paper presents the results of a study of the possibilities of using hydroabrasive cutting to produce standard samples for testing carbon-carbon materials for bending, stretching, compression, etc., to determine ultimate and long-term strength. It is known that the selective ability of the jet (compacted hydroabrasive flow) to flow around obstacles leads to a deviation of the trajectory of its movement, and, as a result, a change in the predicted shape of the cutting groove. For carbon-carbon materials, the problem becomes more acute, since the alternation of high-strength carbon fiber bundles with a softer pyrocarbon phase and a certain hollowness of the structure create conditions for active flow dissipation and blurring of the cross section behind the zone of direct hydroabrasive influence. Another problem is the effect on the properties of the residual moisture that is stored between the fibers.
 It is shown that the rational conditions of water-abrasive cutting and the use of tools to compensate for the jet trajectory distortion allow limiting the zone of destruction to 0.5...0.8 mm and ensuring almost complete removal of moisture from the samples within 60 minutes. Based on the width of the destruction zone, it is proposed to introduce the coefficient of the plane of the active section of the sample, which considers these features of the process.