Hypervelocity impact investigations of composite truss tubes for in orbit assembly risk assessment

As the number of orbital structures increases, so does the threat posed by micrometeoroid and orbital debris (MMOD) impacts. These impacts range from the ballistic range (less than 1.5 km/s) to exceeding 20 km/s and can significantly weaken space structures such as the International Space Station (ISS), leading to further risk as the debris shed could damage the in-orbit assembly field. Space structures, including the James Webb Space Telescope (JWST) and the in-space assembled telescope (ISAT), often employ fiber-matrix composites in various shapes and sizes. While the effects of hypervelocity impacts (HVI) on flat plate composites have been extensively studied, there is a notable lack of research on HVI of composite tubes. Understanding how MMOD impacts affect the integrity of individual truss members, as well as the structure as a whole is essential for assessing the condition of existing space structures and improving future designs. To replicate MMOD impacts, HVI investigations from 1 to over 3 km/s were conducted on a specialized two-stage light-gas gun, showing the transition from single inlet wall damage to cascading internal fragmentation inside the tube, leading to increased damage with increasing velocity. Our investigation focuses on the image analysis of the damage area and ejecta fragmentation in the carbon fiber reinforced polymer (CFRP) tubes, as well as quantifying the resulting hole diameter. This data is crucial for validating corresponding computational models. In this study we present three separate methods of characterizing HVI including: impedance matching through equations of state, a hybrid Lagrangian finite element (FE) model using LS-DYNA with smoothed particle hydrodynamics (SPH), and experimental investigations. All methods agree that HVI can cause nearly three times the amount of damage within a tube compared to similar conditions on a plate. Our findings help enhance our understanding of MMOD impact risks on existing structures and contribute to the development of systems with greater resilience to HVI.