Formation mechanism and damage characteristics of a high-entropy alloy/Al/PTFE double-layer composite liner with a truncated inner layer

Aiming at the limitations of traditional metal jets in penetrating concrete targets, such as limited damage range and insufficient dynamic response, a novel double-layer energetic composite liner structure with a truncated inner layer made of high-entropy alloys/aluminum/polytetrafluoroethylene (HEA/Al/PTFE) was proposed for the first time. The hemispherical composite liner’s HEA layer was prepared using vacuum arc melting, while the Al/PTFE inner layer was formed through powder compaction and sintering. To thoroughly verify the performance advantages of the composite liner, two types of shaped charge structures were fabricated during the experimental phase for comparison: one with the composite liner and the other with a single-layer HEA liner. C35 plain concrete cylinders were used as targets, with single-point initiation at the center of the charge top. Additionally, numerical simulations of the jet formation process were conducted using the commercial finite element software ANSYS-LS-DYNA. The explosive and liner were modeled with the Smoothed Particle Hydrodynamics (SPH) algorithm to accurately capture the dispersal behavior during jet formation, while the casing was simulated with the Lagrangian algorithm to describe the expansion and fragmentation process of the outer shell. In the simulation, the high-temperature and high-strain-rate mechanical behaviors of HEA, Al/PTFE, and 45 steel were described using the Johnson-Cook constitutive model. The explosive was modeled with the classical JWL equation of state, and air was treated as an ideal gas. All relevant parameters were sourced from published literature. Based on the axisymmetric curvature characteristics of the hemispherical liner and the material discontinuity introduced by truncation, a partitioned formation theoretical model was further established. An energy loss coefficient η (η=0.2) was introduced to modify the detonation energy transfer process. According to the truncation angle, the composite liner was divided into two regions with different physical mechanisms. The jet radius and slug radius for each region were derived using mass and momentum conservation. Experimental results show that both the composite liner and the single-layer HEA liner can form stable penetrating jets, achieving complete penetration of the concrete targets. Compared to the single-layer HEA liner, the composite structure significantly enhances the fragmentation and crack propagation capabilities inside the concrete. Numerical simulation results indicate that the Al/PTFE inner layer exhibits a “coating and cohesive” effect on the HEA jet, effectively suppressing radial dispersion and improving the continuity of the mid-section of the jet. However, multiple collision-following-separation behaviors between the inner layer and the main jet delay the system from reaching dynamic equilibrium. The established partitioned formation theoretical model demonstrates good predictive accuracy, with relative errors of less than 15% between the predicted jet and slug radii and the numerical simulation results. Further parametric analysis reveals that the thickness and height of the inner layer significantly influence jet formation. The optimal parameter combination is a thickness of 3.5 mm and a height of 12 mm, which achieves the best balance between suppressing radial dispersion, maintaining jet length, and enhancing mid-section cohesion. This composite liner effectively integrates the excellent mechanical properties of HEA with the high energy release characteristics of Al/PTFE. The established partitioned formation theoretical model provides a reliable theoretical basis for the design of hemispherical composite liners. The research findings offer important theoretical and experimental support for the optimized design and engineering application of novel energetic composite liners.