Research on the ignition process and mechanism of reactive fragments hitting aircraft fuel tanks

Compared with inert fragments, reactive fragments exhibit an ignition-enhancing damage effect on aircraft fuel tanks. However, research on the ignition process and mechanism of fuel tanks impacted by reactive fragments is not deep enough, mainly due to insufficient focus on the behavior of reactive fragments within the tank and the state of the gas phase layer. In this study, we ascertained a new ignition process and revealed the ignition mechanism when reactive fragments hit the gas phase layers of a non-full tank. First, we conducted damage tests on a non-full fuel tank with reactive fragments. Several new phenomena were discovered, such as internal ignition from reactive fragments impacting a non-full fuel tank and the reignition of the fuel tank. Second, based on the test results and the state of the gas phase layer inside the tank, we ascertained a typical six-stage ignition process for the fuel tank impacted by reactive fragments. Finally, using the real internal pressure of the fuel tank during impact tests and the ignition delay curve, we revealed the ignition mechanism of reactive fragments. The research results show that the ascertained ignition process and mechanism align with high-speed photography of reactive fragment impacts on an internally viewable fuel tank. Related research can provide critical insights for assessing reactive fragment threats to aircraft fuel tanks and optimizing their ballistic protection.