This thesis focuses on the design and structural analysis of a bicycle frame made of composite material. Given the increasing necessity of reducing waste and recycling, the aim is to analyse its behavior when made with natural fiber reinforced composite compared to carbon fiber, looking for a trade off between sustainability and performance. It has been decided to apply these kind of materials on a bicycle typically used by amateurs, that can ride both on road both off road: a gravel bike. The first section of the paper deals with design itself of the frame and explains the geometrical choices and constraints given by calculations, experience and standards developed through the years in the cycling world.