Thermal response and reaction evolution of CL-20-based aluminized explosives under varying casing constraints

As a typical high-energy material system, the impact ignition and thermal response characteristics of CL-20-based explosives are crucial for their safety design and engineering applications. This study combines experimental and numerical simulation methods to systematically reveal the reaction evolution mechanisms of CL-20-based explosives under both unconfined shock loads and thermal loads with varying shell confinements. For the shock ignition characteristics, key parameters of the three-term ignition growth reaction rate equation (FREQ = 1.78 × 10¹⁰, GROW1 = 200, GROW2 = 176) were calibrated using Laue tests and numerical simulations. The average pressure peak error between experiments and simulations was 6.92% (R² = 0.96), validating the reliability of the model. Further experiments on shell confinement under thermal loading showed that shell thickness significantly influenced heat conduction paths and energy release characteristics. The thick shell (15 mm) delayed the ignition time to 8825 s (a 2.9% increase compared to the thinner shell) and raised the maximum internal pressure by 58.7% (1437.77 MPa). The reaction degree increased nonlinearly with shell thickness (reaction degree λ = 0.62 for a 3 mm shell, increasing to λ = 0.89 for a 15 mm shell). The numerical model predictions closely matched the experimental data (with a pressure peak error < 5%), revealing that thermal accumulation at the shell corner governs the ignition mechanism. Additionally, enhanced confinement suppressed gas expansion, thus extending the energy release period. The findings provide critical theoretical support for safety performance evaluation and engineering design of CL-20-based explosives.