Study of the crack resistance and fracture mechanism of steel-aluminum composite material

Abstract

Steel-aluminum composite materials are widely used in technology due to perfect wedding of their weight efficiency and high mechanical properties. This is the reason for their wide application in the aerospace industry for manufacturing case-type parts of rockets, fuel tanks and elements of aviation armor. The goal of the study is analysis of the crack resistance and the mechanism of fracture of aluminum-steel composite material (20 vol.%) with a density of 2.85 g/cm 3. The matrix component of the material was obtained using a finely dispersed aluminum powder PAP-2. The reinforcing component was made of steel meshes woven from austenitic steel cable (08Kh17N13M2). The transverse bending strength of the obtained material (550 – 600 MPa) was calculated from the maximum load corresponding to the first jump (onset) of the crack nucleating in the matrix. The crack resistance of the composite material at the stage of fracture initiation (estimated using K 1 c parameter) varied from 15 to 30 MPa · m 1/2 . The crack resistance of the composite at the stage of fracture development was described using the specific effective fracture work γ F ranged from 2 × 10 4 to 8 × 10 4 J/m 2 . The latter parameter exceeds by the order of magnitude the value γ F determined for steel St3, aluminum alloy D16T, and titanium alloy VT-5. The high value of γ F (which is an advantage of the obtained composite) is attributed to high-energy-consuming mechanism of the material fracture provided by the increased energy consumption for the destruction of the bridges between the matrix aluminum layers by cutting them off with a cable resulting from the shear stresses, for overcoming the friction forces when pulling cable out of the matrix, and for shifting layered packets formed by diffusion-bonded aluminum scaly particles inside the matrix. The properties of the obtained steel-aluminum composite provide the expediency of using the material for lightweight structural elements operated under mechanical loading.