This paper describes the operation and performance of an atomic-oxygen (AO) beam facility developed at the University of Toronto Institute for Aerospace Studies (UTIAS), capable of providing ground-state neutral oxygen atoms at ~ 2.2 eV for flux levels as high as ~ 1016 atoms (cm2 s)−1. Results are presented on the AO erosion of polymer thin films and composite materials containing graphite and aramid fibres in epoxy matrices. Comparisons with space flight tests are also given, including studies of samples recently retrieved from the UTIAS composite-materials experiment on the NASA Long Duration Exposure Facility after 70 months exposure in low Earth orbit. Parameters that have been investigated include synergistic effects of UV radiation, surface-morphology changes, and accelerated testing.