An eco-efficient helicopter tailplane hybridized from flax, balsa and carbon

A tailplane for an n ultralight helicopter was redesigned with the goal of using bio-based materials in a high proportion. Structural requirements were set to the national ultralight certification standards and were also adapted from the performance of the initial design tailplane, which was made of carbon prepreg materials and a foam core. In order to pursue this goal, pre-impregnated flax fiber composites, in combination with a balsa wood core and a small proportion of carbon fiber reinforcements, were used to design a new tailplane. A finite element model was developed, fed by material data from tensile tests and evolving iteratively from coupon and sub-component bending tests. Finally, a 450 mm section of the resulting design was built and a bio-based mass content of approximately 55 % was achieved. The new, hybrid version was analyzed experimentally in terms of weight, stiffness, strength/ failure, damping, and embodied energy, where benchmark data was obtained from either the reference tailplane or the certification specifications. Benefits of the new design were identified in a 2–8 times higher damping ratio, 65% less embodied energy (76.90 MJ kg⁻¹), and reduced carbon footprint (5 kg kg⁻¹), while weight, stiffness, and strength were performing in a sufficient and comparative manner as the reference.