Deposition dynamics and analysis of polyurethane foam structure boundaries for Aerial Additive Manufacturing

Additive manufacturing in construction typically consists of ground-based platforms. Introducing aerial capabilities offers scope to create or repair structures in dangerous or elevated locations. The Aerial Additive Manufacturing (AAM) project has developed a pioneering approach using Unmanned Aerial Vehicles (UAV, ‘drones’) to deposit material during self-powered, autonomous, untethered flight. This study investigates high and low-density foams autonomously deposited as structural and insulation materials. Drilling resistance, mechanical, thermal and microscopy tests investigate density variation, interfacial integrity and thermal stability. Autonomous deposition is demonstrated using a flying UAV and robotic arm. Results reveal dense material at interfaces and directionally dependent cell expansion during foaming. Cured interfacial regions are vulnerable to loading parallel to interfaces but resistant to perpendicular loading. Mitigation of trajectory printing errors caused by UAV flight disturbance is demonstrated by a stabilising end effector, with trajectory errors ≤10 mm. AAM provides a significant development towards on-site automation in construction. Highlights Aerial Additive Manufacturing (AAM) releases additive manufacturing (AM) for construction applications from ground-based and tethered restraints. Multiple self-powered flying Unmanned Aerial Vehicles (UAV) can deposit layers of polyurethane foam in planned trajectories. High-density polyurethane foam and low-density foam can be suitable for structural and insulating layers, respectively. Laboratory tests, including drilling resistance, demonstrate the high-density of interfacial boundary regions in relation to material located away from a boundary. The challenges of reducing lateral deformation of extruded material are evaluated, and improved flight stabilisation provided by an end effector keeping trajectory errors within 10 mm is demonstrated.