Interlayer Gap Effect on the Dynamics and Strength of Two-Layer Metal Composite Cylinders under Internal Explosion

The effect of contact conditions and the gap between the metal and composite layers on the stress-strain state and strength of a two-layer metal composite cylinder under internal explosive loading in air is numerically studied. It is accepted that in the absence of a gap between the metal and composite layers, there is no interference. The problem was considered on the basis of the general equations of theories of elasticity and plasticity in a one-dimensional formulation (plane strain state), which makes it possible to neglect the peculiarities of loading and deformation along the cylinder length. In the absence of an initial gap, the case of perfect contact between the layers was also studied. The inner layer is made of one or another isotropic elastoplastic steel with significantly different yield strengths (steels 20 and 40KhNMA), the outer one is made of an elastic-to-failure cylindrically transtropic circumferentially reinforced composite The dynamic 1D boundary-value problem was solved using the training version of the LS-DYNA software, which is part of the ANSYS commercial application package. The solution method is the Wilkins finitedifference integro-interpolation algorithm included in above software version. It has been established that the strength of the metal composite cylinder under internal explosion is determined by the strength of the outer composite layer under tension in the radial direction and depends nonlinearly and nonmonotonically on the initial gap between the layers. The maximum strength is realized under perfect or non-perfect contact with zero initial gap, and the minimum strength is realized at the initial gap that is roughly equal to a half of the maximum displacement of the inner steel shell in the case of absence of the outer composite layer. To make the reinforcing inner layer, it is inexpedient to use, in terms of strength, structural alloy steels with high yield strength; the steels with low yield strength are more efficient.