CANTILEVER BENDING AND COMPRESSION PERFORMANCE OF HYBRID COMPOSITE LOAD - BEARING ARMS FOR UNMANNED AERIAL VEHICLES

Abstract

Lightweight load - bearing arms for unmanned aerial vehicles require high bending capacity, sufficient stiffness and stable local compression response at minimum structural mass. This work evaluates ten hybrid composite arm prototypes combining aluminium tubes, aluminium flat bars, aluminium angles or wooden rods with foam core, flax reinforcement and internal ribs. Cantilever bending tests were carried out at 10.0 mm min^-1 and 22.0°C, while short composite tube specimens were additionally tested in compression at room temperature. The maximum bending moment ranged from 260 Nm to 587 Nm. The highest bending moment was obtained for the five - aluminium - flat
configuration with foam and flax reinforcement, whereas the highest bending stiffness, 63.5 N mm^-1, was obtained when the same reinforcement concept also included internal ribs. The compressive strength of the S1 - S10 tube specimens ranged from 14.7 kN to 27.5 kN. The results show that flax/foam hybridisation strongly improves bending load capacity, while ribs mainly improve stiffness and shape stability but must be designed to avoid local stress concentration. The data provide an experimental basis for selecting practical reinforced hybrid composite arms for small UAV airframes.