In this paper, we obtain samples of composite materials with a layered niobium-based matrix unidirectionally reinforced with single-crystal sapphire fibers using the solid-phase method of diffusion welding. Sapphire fibers are obtained by the Stepanov method (EFG). As a result of tests, the dependences of the strength of such fibers on the length are obtained for the first time. The strength values correspond to the global level. X-ray spectral microanalysis of the obtained materials is performed. The formation of solid solutions and intermetallic compounds of the Nb-Al system during composite-structure formation is established. Strength tests (500–700 MPa) are carried out and the effective surface energy of fracture of the composites is determined ((9–49) × 10³ J/m²), and their correlation with the fabrication modes is established. The features of the fracture structure of such materials and the processes inhibiting its fracturing under load are studied.

A mathematical model was developed to determine the order of failure of layers in a two-layer ceramics composite and to determine the conditions for achieving the maximum limit load under three-point loading. The model was set in the space of three “bilayer parameters”: the ratio of the thickness of the lower layer to the whole thickness of the beam, the ratio of Young’s moduli of the lower layer to the upper layer, and the ratio of flexural strengths of the materials of the lower layer to the upper layer. The adequacy of the model obtained was confirmed by experimental results on the three-point bending of the experimental specimens. The experimental samples were two-layer composites consisting of a cermet layer TiB/Ti and a layer of α-Ti. The samples were obtained by free self-propagating high-temperature synthesis (SHS) compression and with varying their thickness. The results obtained make it possible to predict in advance which layer, based on the specific bilayer parameters, will trigger the brittle fracture mechanism as well as to set the maximum destructive load of bilayer composites.

The article deals with brittle failure of a two-layer beam under three-point loading conditions depending on the parameters under consideration — different proportions of thicknesses, Young’s moduli and strengths of both layers. Based on the equations of force and moment equilibrium, the dependences of the position of the beam neutral axis and its curvature are derived and the regions of parameters are determined, at which the failure begins earlier in the layer to which the load is applied than in the outer opposite layer to the load.

The problem of delayed fracture and long-term strength of multilayer composites represents not only fundamental but also applied interest. The proposed sol

Проблема замедленного разрушения и длительной прочности многослойных композитов представляет не только фундаментальный, но и прикладной интерес. Предложенное решение позволяет оценить влияние геометрии, структуры и соотношения свойств слоистого композита на его долговечность. Время до разрушения двухслойной металлической балки прямоугольного сечения определяется в зависимости от отношения толщин слоев и их модулей Юнга.