Study of the physicomechanical properties of full-scale objects of carbon-ceramic composite materials of the SiC–C system (communication 3)

Abstract

The physical and mechanical properties and their dispersion in carbon-ceramic composite materials of complex shaped objects are studied. Features of their difference in relation to production methods for manufacturing carbon-reinforced plastic preform-precursors are established. For objects of one geometric shape contemporary technology provides steady reproduction of a single level of mechanical properties and a statistically stable level of production residual internal stresses. In fact, the level of material properties for full-scale objects made of carbon-ceramic composite materials provides the possibility of the their operation with a reliability of not less than 0.99 with an external load from 22 to 50% of the original strength level. The limits established are connected with presence in a structure of holes for securing components.The aim of this work is a study of the physicomechanical properties of the material of large full-scale components of carbon-ceramic composite material (CCCM) of the SiC-C system, and also evaluation and establishment of the permissible limits of their strength operating capacity. Sample size and the overall form of test objects are shown in Fig. 1. Components are an arched integral structure consisting of a thin-walled open shell fastened by two rows of stiffening ribs (Fig. 2). The ribs perform the function of fastening the heat-resistant components of CCCM to a heavy-duty structure, and also increasing the stiffness and supporting capacity of the shell during manufacture and operation. The thickness of the shell d = 8 -12 mm comprising a 0.012 -0.015-th fraction of its height, or 0.006 -0.0067 fraction of the opening of the arch over its base. The width of a stiffening rib is from 80 -120 mm with a thickness up to 22 mm.The importance of developing the technology of these large components is currently increasing. In contemporary non-metallic engineering there is greater use of large composite equipment. With use of equipment made from composite materials the components are manufactured with sizes to several meters. As a result of the economic profitability of composite components there is a higher potential than for similar structures made of traditional materials. Large carbon equipment of integral construction (the firm Nova-Tech Engineering, Lynnwood, Washington) [1] is prepared by autoclave molding of the prepreg bundle. Such equipment has a linear thermal expansion coefficient (LTEC) equal to that of material of the future molded composite component. With sizes of mandrels and components pressed on them up to 5 m this of considerable practical importance. Carbon-reinforced plastic (in the case of using heat-resistant bismaleimide binder within the composition) the equipment has a working capacity of thousands of hours and they are suitable for preparing hundreds of compacts with a level of working temperature of~200°C [1,2]. In the case of preparing this pressequipment of carbon-carbon composites it becomes possible to use it in air up to the melting temperature for alum...