Effects of vents distribution on the flame propagation and dynamic fracture of combustible tubes: Experimental and fluid-structure interaction simulations

Combustible ignition tubes redistribute primer energy within modular charges through internal combustion, venting, and subsequent tube rupture. Their performance is governed jointly by the spatiotemporal release of hot products through vent holes and the transient structural response to the internal pressure field. This study combines X-ray computed tomography (XCT), visual flame-transmission experiments, and a sequentially coupled gas-solid numerical framework to examine these processes for uniform, central, and front vent distributions. XCT reveals a layered, rolled fibrous architecture in the tube wall. The visual experiments establish the relative flame-development and pressure-response characteristics of the three distributions. The numerical model couples a gas-solid interior-ballistics formulation to an explicit finite-element rupture analysis using an orthotropic elastic-plastic-damage representation of the tube. Calculated pressure histories reproduce the measured trends and support interpretation of the rupture sequence. Uniformly distributed holes promote the most balanced pressure release and yield a reproducible terminal, approximately symmetric petal-like rupture. Centralized holes delay failure but promote distributed mid-span fragmentation, while front holes induce an asymmetric terminal tear. The results identify vent-hole distribution as a practical design variable for balancing flame-transmission uniformity, pressure moderation, and controlled rupture.